[PATCHES][RFC] the meat of tree-in-dcache series

[PATCHES][RFC] the meat of tree-in-dcache series

[Al Viro]

[my apologies for the size of patchbomb and the size of Cc; this series
really affects a lot of places, if lightly]

Some filesystems use a kinda-sorta controlled dentry refcount leak to pin
dentries of created objects in dcache (and undo it when removing those).
Reference is grabbed and not released, but it's not actually _stored_
anywhere.  That works, but it's hard to follow and verify; among other
things, we have no way to tell _which_ of the increments is intended
to be an unpaired one.  Worse, on removal we need to decide whether
the reference had already been dropped, which can be non-trivial if
that removal is on umount and we need to figure out if this dentry is
pinned due to e.g. unlink() not done.  Usually that is handled by using
kill_litter_super() as ->kill_sb(), but there are open-coded special
cases of the same (consider e.g. /proc/self).

Things get simpler if we introduce a new dentry flag (DCACHE_PERSISTENT)
marking those "leaked" dentries.  Having it set claims responsibility
for +1 in refcount.

The end result this series is aiming for:

* get these unbalanced dget() and dput() replaced with new primitives that
  would, in addition to adjusting refcount, set and clear persistency flag.
* instead of having kill_litter_super() mess with removing the remaining
  "leaked" references (e.g. for all tmpfs files that hadn't been removed
  prior to umount), have the regular shrink_dcache_for_umount() strip
  DCACHE_PERSISTENT of all dentries, dropping the corresponding
  reference if it had been set.  After that kill_litter_super() becomes
  an equivalent of kill_anon_super().

Doing that in a single step is not feasible - it would affect too many places
in too many filesystems.  It has to be split into a series.

This work has really started early in 2024; quite a few preliminary pieces
have already gone into mainline.  This chunk is finally getting to the
meat of that stuff - infrastructure and most of the conversions to it.

Some pieces are still sitting in the local branches, but the bulk of
that stuff is here.

The branch is -rc5-based; it lives in
git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git #work.persistency
individual patches in followups.

Please, help with review and testing; it does appear to survive the local beating,
but extra eyes on it would be very welcome.

First two commits add a couple of useful helpers, the next three add the
infrastructure and the rest consists of per-filesystem conversions.

Shortlog:
      new helper: simple_remove_by_name()
      new helper: simple_done_creating()
      introduce a flag for explicitly marking persistently pinned dentries
      primitives for maintaining persisitency
      convert simple_{link,unlink,rmdir,rename,fill_super}() to new primitives
      convert ramfs and tmpfs
      procfs: make /self and /thread_self dentries persistent
      configfs, securityfs: kill_litter_super() not needed
      convert xenfs
      convert smackfs
      convert hugetlbfs
      convert mqueue
      convert bpf
      convert dlmfs
      convert fuse_ctl
      convert pstore
      convert tracefs
      convert debugfs
      debugfs: remove duplicate checks in callers of start_creating()
      convert efivarfs
      convert spufs
      convert ibmasmfs
      ibmasmfs: get rid of ibmasmfs_dir_ops
      convert devpts
      binderfs: use simple_start_creating()
      binderfs_binder_ctl_create(): kill a bogus check
      convert binderfs
      autofs_{rmdir,unlink}: dentry->d_fsdata->dentry == dentry there
      convert autofs
      convert binfmt_misc
      convert selinuxfs
      functionfs: switch to simple_remove_by_name()
      convert functionfs
      gadgetfs: switch to simple_remove_by_name()
      convert gadgetfs
      hypfs: don't pin dentries twice
      hypfs: switch hypfs_create_str() to returning int
      hypfs: swich hypfs_create_u64() to returning int
      convert hypfs

Diffstat:
 arch/powerpc/platforms/cell/spufs/inode.c | 15 ++---
 arch/s390/hypfs/hypfs.h                   |  6 +-
 arch/s390/hypfs/hypfs_diag_fs.c           | 60 +++++++-------------
 arch/s390/hypfs/hypfs_vm_fs.c             | 21 +++----
 arch/s390/hypfs/inode.c                   | 82 +++++++++------------------
 drivers/android/binderfs.c                | 82 +++++++--------------------
 drivers/base/devtmpfs.c                   |  2 +-
 drivers/misc/ibmasm/ibmasmfs.c            | 24 ++++----
 drivers/usb/gadget/function/f_fs.c        | 54 ++++++++----------
 drivers/usb/gadget/legacy/inode.c         | 49 ++++++++--------
 drivers/xen/xenfs/super.c                 |  2 +-
 fs/autofs/inode.c                         |  2 +-
 fs/autofs/root.c                          | 11 ++--
 fs/binfmt_misc.c                          | 69 +++++++++++------------
 fs/configfs/mount.c                       |  2 +-
 fs/dcache.c                               | 93 ++++++++++++++++++++++++-------
 fs/debugfs/inode.c                        | 32 +++--------
 fs/devpts/inode.c                         | 57 +++++++------------
 fs/efivarfs/inode.c                       |  7 +--
 fs/efivarfs/super.c                       |  5 +-
 fs/fuse/control.c                         | 19 ++++---
 fs/hugetlbfs/inode.c                      | 12 ++--
 fs/libfs.c                                | 31 +++++++++--
 fs/ocfs2/dlmfs/dlmfs.c                    |  8 +--
 fs/proc/base.c                            |  6 +-
 fs/proc/internal.h                        |  1 +
 fs/proc/root.c                            | 14 ++---
 fs/proc/self.c                            | 10 +---
 fs/proc/thread_self.c                     | 11 +---
 fs/pstore/inode.c                         |  7 ++-
 fs/ramfs/inode.c                          |  8 +--
 fs/tracefs/event_inode.c                  |  4 +-
 fs/tracefs/inode.c                        | 13 ++---
 include/linux/dcache.h                    |  3 +
 include/linux/fs.h                        |  3 +
 include/linux/proc_fs.h                   |  2 -
 init/do_mounts.c                          |  2 +-
 ipc/mqueue.c                              | 12 +---
 kernel/bpf/inode.c                        | 15 ++---
 mm/shmem.c                                | 23 ++------
 security/inode.c                          |  2 +-
 security/selinux/selinuxfs.c              | 52 +++++++++--------
 security/smack/smackfs.c                  |  2 +-
 43 files changed, 412 insertions(+), 523 deletions(-)

[PATCH 01/39] new helper: simple_remove_by_name()

[Al Viro]

simple_recursive_removal(), but instead of victim dentry it takes
parent + name.

Used to be open-coded in fs/fuse/control.c, but there's no need to expose
the guts of that thing there and there are other potential users, so
let's lift it into libfs...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/fuse/control.c  |  7 +------
 fs/libfs.c         | 13 +++++++++++++
 include/linux/fs.h |  2 ++
 3 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/fs/fuse/control.c b/fs/fuse/control.c
index bb407705603c..31fa816d0189 100644
--- a/fs/fuse/control.c
+++ b/fs/fuse/control.c
@@ -289,18 +289,13 @@ static void remove_one(struct dentry *dentry)
  */
 void fuse_ctl_remove_conn(struct fuse_conn *fc)
 {
-	struct dentry *dentry;
 	char name[32];
 
 	if (!fuse_control_sb || fc->no_control)
 		return;
 
 	sprintf(name, "%u", fc->dev);
-	dentry = lookup_noperm_positive_unlocked(&QSTR(name), fuse_control_sb->s_root);
-	if (!IS_ERR(dentry)) {
-		simple_recursive_removal(dentry, remove_one);
-		dput(dentry);	// paired with lookup_noperm_positive_unlocked()
-	}
+	simple_remove_by_name(fuse_control_sb->s_root, name, remove_one);
 }
 
 static int fuse_ctl_fill_super(struct super_block *sb, struct fs_context *fsc)
diff --git a/fs/libfs.c b/fs/libfs.c
index ce8c496a6940..d029aff41f66 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -655,6 +655,19 @@ void simple_recursive_removal(struct dentry *dentry,
 }
 EXPORT_SYMBOL(simple_recursive_removal);
 
+void simple_remove_by_name(struct dentry *parent, const char *name,
+                           void (*callback)(struct dentry *))
+{
+	struct dentry *dentry;
+
+	dentry = lookup_noperm_positive_unlocked(&QSTR(name), parent);
+	if (!IS_ERR(dentry)) {
+		simple_recursive_removal(dentry, callback);
+		dput(dentry);	// paired with lookup_noperm_positive_unlocked()
+	}
+}
+EXPORT_SYMBOL(simple_remove_by_name);
+
 /* caller holds parent directory with I_MUTEX_PARENT */
 void locked_recursive_removal(struct dentry *dentry,
                               void (*callback)(struct dentry *))
diff --git a/include/linux/fs.h b/include/linux/fs.h
index d7ab4f96d705..3a33c68249e2 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3628,6 +3628,8 @@ extern int simple_rename(struct mnt_idmap *, struct inode *,
 			 unsigned int);
 extern void simple_recursive_removal(struct dentry *,
                               void (*callback)(struct dentry *));
+extern void simple_remove_by_name(struct dentry *, const char *,
+                              void (*callback)(struct dentry *));
 extern void locked_recursive_removal(struct dentry *,
                               void (*callback)(struct dentry *));
 extern int noop_fsync(struct file *, loff_t, loff_t, int);
-- 
2.47.3

[PATCH 02/39] new helper: simple_done_creating()

[Al Viro]

should be paired with simple_start_creating() - unlocks parent and
drops dentry reference.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/libfs.c         | 8 ++++++++
 include/linux/fs.h | 1 +
 2 files changed, 9 insertions(+)

diff --git a/fs/libfs.c b/fs/libfs.c
index d029aff41f66..a033f35493d0 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -2326,3 +2326,11 @@ struct dentry *simple_start_creating(struct dentry *parent, const char *name)
 	return dentry;
 }
 EXPORT_SYMBOL(simple_start_creating);
+
+/* parent must have been held exclusive since simple_start_creating() */
+void simple_done_creating(struct dentry *child)
+{
+	inode_unlock(child->d_parent->d_inode);
+	dput(child);
+}
+EXPORT_SYMBOL(simple_done_creating);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3a33c68249e2..e3000302c3b9 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3659,6 +3659,7 @@ extern int simple_fill_super(struct super_block *, unsigned long,
 extern int simple_pin_fs(struct file_system_type *, struct vfsmount **mount, int *count);
 extern void simple_release_fs(struct vfsmount **mount, int *count);
 struct dentry *simple_start_creating(struct dentry *, const char *);
+void simple_done_creating(struct dentry *);
 
 extern ssize_t simple_read_from_buffer(void __user *to, size_t count,
 			loff_t *ppos, const void *from, size_t available);
-- 
2.47.3

[PATCH 03/39] introduce a flag for explicitly marking persistently pinned dentries

[Al Viro]

Some filesystems use a kinda-sorta controlled dentry refcount leak to pin
dentries of created objects in dcache (and undo it when removing those).
Reference is grabbed and not released, but it's not actually _stored_
anywhere.  That works, but it's hard to follow and verify; among other
things, we have no way to tell _which_ of the increments is intended
to be an unpaired one.  Worse, on removal we need to decide whether
the reference had already been dropped, which can be non-trivial if
that removal is on umount and we need to figure out if this dentry is
pinned due to e.g. unlink() not done.  Usually that is handled by using
kill_litter_super() as ->kill_sb(), but there are open-coded special
cases of the same (consider e.g. /proc/self).

Things get simpler if we introduce a new dentry flag (DCACHE_PERSISTENT)
marking those "leaked" dentries.  Having it set claims responsibility
for +1 in refcount.

The end result this series is aiming for:

* get these unbalanced dget() and dput() replaced with new primitives that
  would, in addition to adjusting refcount, set and clear persistency flag.
* instead of having kill_litter_super() mess with removing the remaining
  "leaked" references (e.g. for all tmpfs files that hadn't been removed
  prior to umount), have the regular shrink_dcache_for_umount() strip
  DCACHE_PERSISTENT of all dentries, dropping the corresponding
  reference if it had been set.  After that kill_litter_super() becomes
  an equivalent of kill_anon_super().

Doing that in a single step is not feasible - it would affect too many places
in too many filesystems.  It has to be split into a series.

Here we
	* introduce the new flag
	* teach shrink_dcache_for_umount() to handle it (i.e. remove
and drop refcount on anything that survives to umount with that flag
still set)
	* teach kill_litter_super() that anything with that flag does
*not* need to be unpinned.

Next commits will add primitives for maintaing that flag and convert the
common helpers to those.  After that - a long series of per-filesystem
patches converting to those primitives.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/dcache.c            | 27 ++++++++++++++++++++++-----
 include/linux/dcache.h |  1 +
 2 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index 60046ae23d51..e34290e15fd2 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1511,6 +1511,15 @@ static enum d_walk_ret select_collect(void *_data, struct dentry *dentry)
 	return ret;
 }
 
+static enum d_walk_ret select_collect_umount(void *_data, struct dentry *dentry)
+{
+	if (dentry->d_flags & DCACHE_PERSISTENT) {
+		dentry->d_flags &= ~DCACHE_PERSISTENT;
+		dentry->d_lockref.count--;
+	}
+	return select_collect(_data, dentry);
+}
+
 static enum d_walk_ret select_collect2(void *_data, struct dentry *dentry)
 {
 	struct select_data *data = _data;
@@ -1539,18 +1548,20 @@ static enum d_walk_ret select_collect2(void *_data, struct dentry *dentry)
 }
 
 /**
- * shrink_dcache_parent - prune dcache
+ * shrink_dcache_tree - prune dcache
  * @parent: parent of entries to prune
+ * @for_umount: true if we want to unpin the persistent ones
  *
  * Prune the dcache to remove unused children of the parent dentry.
  */
-void shrink_dcache_parent(struct dentry *parent)
+static void shrink_dcache_tree(struct dentry *parent, bool for_umount)
 {
 	for (;;) {
 		struct select_data data = {.start = parent};
 
 		INIT_LIST_HEAD(&data.dispose);
-		d_walk(parent, &data, select_collect);
+		d_walk(parent, &data,
+			for_umount ? select_collect_umount : select_collect);
 
 		if (!list_empty(&data.dispose)) {
 			shrink_dentry_list(&data.dispose);
@@ -1575,6 +1586,11 @@ void shrink_dcache_parent(struct dentry *parent)
 			shrink_dentry_list(&data.dispose);
 	}
 }
+
+void shrink_dcache_parent(struct dentry *parent)
+{
+	shrink_dcache_tree(parent, false);
+}
 EXPORT_SYMBOL(shrink_dcache_parent);
 
 static enum d_walk_ret umount_check(void *_data, struct dentry *dentry)
@@ -1601,7 +1617,7 @@ static enum d_walk_ret umount_check(void *_data, struct dentry *dentry)
 
 static void do_one_tree(struct dentry *dentry)
 {
-	shrink_dcache_parent(dentry);
+	shrink_dcache_tree(dentry, true);
 	d_walk(dentry, dentry, umount_check);
 	d_drop(dentry);
 	dput(dentry);
@@ -3108,7 +3124,8 @@ static enum d_walk_ret d_genocide_kill(void *data, struct dentry *dentry)
 {
 	struct dentry *root = data;
 	if (dentry != root) {
-		if (d_unhashed(dentry) || !dentry->d_inode)
+		if (d_unhashed(dentry) || !dentry->d_inode ||
+		    dentry->d_flags & DCACHE_PERSISTENT)
 			return D_WALK_SKIP;
 
 		if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index cc3e1c1a3454..946f40168c73 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -222,6 +222,7 @@ enum dentry_flags {
 	DCACHE_PAR_LOOKUP		= BIT(24),	/* being looked up (with parent locked shared) */
 	DCACHE_DENTRY_CURSOR		= BIT(25),
 	DCACHE_NORCU			= BIT(26),	/* No RCU delay for freeing */
+	DCACHE_PERSISTENT		= BIT(27)
 };
 
 #define DCACHE_MANAGED_DENTRY \
-- 
2.47.3

[PATCH 04/39] primitives for maintaining persisitency

[Al Viro]

* d_make_persistent(dentry, inode) - bump refcount, mark persistent and
make hashed positive.  Return value is a borrowed reference to dentry;
it can be used until something removes persistency (at the very least,
until the parent gets unlocked, but some filesystems may have stronger
exclusion).

* d_make_discardable() - remove persistency mark and drop reference.

d_make_persistent() is similar to combination of d_instantiate(), dget()
and setting flag.  The only difference is that unlike d_instantiate()
it accepts hashed and unhashed negatives alike.  It is always called in
strong locking environment (parent held exclusive); if we ever start using
it with parent held only shared, we'll need to copy the in-lookup logics
from __d_add().

d_make_discardable() is eqiuvalent to combination of removing flag and
dput(); since flag removal requires ->d_lock, there's no point trying
to avoid taking that for refcount decrement as fast_dput() does.
The slow path of dput() has been taken into a helper and reused in
d_make_discardable() instead.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/dcache.c            | 66 ++++++++++++++++++++++++++++++++----------
 include/linux/dcache.h |  2 ++
 2 files changed, 53 insertions(+), 15 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index e34290e15fd2..9f802f6f9e3b 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -869,6 +869,24 @@ static inline bool fast_dput(struct dentry *dentry)
 	return false;
 }
 
+static void finish_dput(struct dentry *dentry)
+	__releases(dentry->d_lock)
+	__releases(RCU)
+{
+	while (lock_for_kill(dentry)) {
+		rcu_read_unlock();
+		dentry = __dentry_kill(dentry);
+		if (!dentry)
+			return;
+		if (retain_dentry(dentry, true)) {
+			spin_unlock(&dentry->d_lock);
+			return;
+		}
+		rcu_read_lock();
+	}
+	rcu_read_unlock();
+	spin_unlock(&dentry->d_lock);
+}
 
 /* 
  * This is dput
@@ -906,22 +924,20 @@ void dput(struct dentry *dentry)
 		rcu_read_unlock();
 		return;
 	}
-	while (lock_for_kill(dentry)) {
-		rcu_read_unlock();
-		dentry = __dentry_kill(dentry);
-		if (!dentry)
-			return;
-		if (retain_dentry(dentry, true)) {
-			spin_unlock(&dentry->d_lock);
-			return;
-		}
-		rcu_read_lock();
-	}
-	rcu_read_unlock();
-	spin_unlock(&dentry->d_lock);
+	finish_dput(dentry);
 }
 EXPORT_SYMBOL(dput);
 
+void d_make_discardable(struct dentry *dentry)
+{
+	spin_lock(&dentry->d_lock);
+	dentry->d_flags &= ~DCACHE_PERSISTENT;
+	dentry->d_lockref.count--;
+	rcu_read_lock();
+	finish_dput(dentry);
+}
+EXPORT_SYMBOL(d_make_discardable);
+
 static void to_shrink_list(struct dentry *dentry, struct list_head *list)
 __must_hold(&dentry->d_lock)
 {
@@ -1939,7 +1955,6 @@ static void __d_instantiate(struct dentry *dentry, struct inode *inode)
 	unsigned add_flags = d_flags_for_inode(inode);
 	WARN_ON(d_in_lookup(dentry));
 
-	spin_lock(&dentry->d_lock);
 	/*
 	 * The negative counter only tracks dentries on the LRU. Don't dec if
 	 * d_lru is on another list.
@@ -1952,7 +1967,6 @@ static void __d_instantiate(struct dentry *dentry, struct inode *inode)
 	__d_set_inode_and_type(dentry, inode, add_flags);
 	raw_write_seqcount_end(&dentry->d_seq);
 	fsnotify_update_flags(dentry);
-	spin_unlock(&dentry->d_lock);
 }
 
 /**
@@ -1976,7 +1990,9 @@ void d_instantiate(struct dentry *entry, struct inode * inode)
 	if (inode) {
 		security_d_instantiate(entry, inode);
 		spin_lock(&inode->i_lock);
+		spin_lock(&entry->d_lock);
 		__d_instantiate(entry, inode);
+		spin_unlock(&entry->d_lock);
 		spin_unlock(&inode->i_lock);
 	}
 }
@@ -1995,7 +2011,9 @@ void d_instantiate_new(struct dentry *entry, struct inode *inode)
 	lockdep_annotate_inode_mutex_key(inode);
 	security_d_instantiate(entry, inode);
 	spin_lock(&inode->i_lock);
+	spin_lock(&entry->d_lock);
 	__d_instantiate(entry, inode);
+	spin_unlock(&entry->d_lock);
 	WARN_ON(!(inode->i_state & I_NEW));
 	inode->i_state &= ~I_NEW & ~I_CREATING;
 	/*
@@ -2752,6 +2770,24 @@ void d_add(struct dentry *entry, struct inode *inode)
 }
 EXPORT_SYMBOL(d_add);
 
+struct dentry *d_make_persistent(struct dentry *dentry, struct inode *inode)
+{
+	BUG_ON(!hlist_unhashed(&dentry->d_u.d_alias));
+	BUG_ON(!inode);
+	security_d_instantiate(dentry, inode);
+	spin_lock(&inode->i_lock);
+	spin_lock(&dentry->d_lock);
+	__d_instantiate(dentry, inode);
+	dentry->d_flags |= DCACHE_PERSISTENT;
+	dget_dlock(dentry);
+	if (d_unhashed(dentry))
+		__d_rehash(dentry);
+	spin_unlock(&dentry->d_lock);
+	spin_unlock(&inode->i_lock);
+	return dentry;
+}
+EXPORT_SYMBOL(d_make_persistent);
+
 static void swap_names(struct dentry *dentry, struct dentry *target)
 {
 	if (unlikely(dname_external(target))) {
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 946f40168c73..77c205693ef8 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -608,5 +608,7 @@ static inline struct dentry *d_next_sibling(const struct dentry *dentry)
 }
 
 void set_default_d_op(struct super_block *, const struct dentry_operations *);
+struct dentry *d_make_persistent(struct dentry *, struct inode *);
+void d_make_discardable(struct dentry *dentry);
 
 #endif	/* __LINUX_DCACHE_H */
-- 
2.47.3

[PATCH 05/39] convert simple_{link,unlink,rmdir,rename,fill_super}() to new primitives

[Al Viro]

Note that simple_unlink() et.al. are used by many filesystems; for now
they can not assume that persistency mark will have been set back
when the object got created.  Once all conversions are done we'll
have them complain if called for something that had not been marked
persistent.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/libfs.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/fs/libfs.c b/fs/libfs.c
index a033f35493d0..80f288a771e3 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -630,7 +630,7 @@ static void __simple_recursive_removal(struct dentry *dentry,
 				if (callback)
 					callback(victim);
 				fsnotify_delete(inode, d_inode(victim), victim);
-				dput(victim);		// unpin it
+				d_make_discardable(victim);
 			}
 			if (victim == dentry) {
 				inode_set_mtime_to_ts(inode,
@@ -764,8 +764,7 @@ int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *den
 			      inode_set_ctime_to_ts(dir, inode_set_ctime_current(inode)));
 	inc_nlink(inode);
 	ihold(inode);
-	dget(dentry);
-	d_instantiate(dentry, inode);
+	d_make_persistent(dentry, inode);
 	return 0;
 }
 EXPORT_SYMBOL(simple_link);
@@ -798,7 +797,7 @@ int simple_unlink(struct inode *dir, struct dentry *dentry)
 	inode_set_mtime_to_ts(dir,
 			      inode_set_ctime_to_ts(dir, inode_set_ctime_current(inode)));
 	drop_nlink(inode);
-	dput(dentry);
+	d_make_discardable(dentry);
 	return 0;
 }
 EXPORT_SYMBOL(simple_unlink);
@@ -1078,7 +1077,8 @@ int simple_fill_super(struct super_block *s, unsigned long magic,
 		simple_inode_init_ts(inode);
 		inode->i_fop = files->ops;
 		inode->i_ino = i;
-		d_add(dentry, inode);
+		d_make_persistent(dentry, inode);
+		dput(dentry);
 	}
 	return 0;
 }
-- 
2.47.3

[PATCH 06/39] convert ramfs and tmpfs

[Al Viro]

Quite a bit is already done by infrastructure changes (simple_link(),
simple_unlink()) - all that is left is replacing d_instantiate() +
pinning dget() (in ->symlink() and ->mknod()) with d_make_persistent(),
and, in case of shmem, unpinning dput() in ->unlink() with d_make_discardable().
Since d_make_persistent() accepts (and hashes) unhashed ones,
shmem situation gets simpler - we no longer care whether ->lookup()
has hashed the sucker.

With that done, we don't need kill_litter_super() for these filesystems
anymore - by the umount time all remaining dentries will be marked
persistent and kill_litter_super() will boil down to call of
kill_anon_super().

The same goes for devtmpfs and rootfs - they are handled by
ramfs or by shmem, depending upon config.

NB: strictly speaking, both devtmpfs and rootfs ought to use
ramfs_kill_sb() if they end up using ramfs; that's a separate
story and the only impact of "just use kill_{litter,anon}_super()"
is that we fail to free their sb->s_fs_info... on reboot.
That's orthogonal to the changes in this series - kill_litter_super()
is identical to kill_anon_super() for those at this point.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 drivers/base/devtmpfs.c |  2 +-
 fs/ramfs/inode.c        |  8 +++-----
 init/do_mounts.c        |  2 +-
 mm/shmem.c              | 23 +++++------------------
 4 files changed, 10 insertions(+), 25 deletions(-)

diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
index 31bfb3194b4c..30b5ae8d79cf 100644
--- a/drivers/base/devtmpfs.c
+++ b/drivers/base/devtmpfs.c
@@ -70,7 +70,7 @@ static struct file_system_type internal_fs_type = {
 #else
 	.init_fs_context = ramfs_init_fs_context,
 #endif
-	.kill_sb = kill_litter_super,
+	.kill_sb = kill_anon_super,
 };
 
 /* Simply take a ref on the existing mount */
diff --git a/fs/ramfs/inode.c b/fs/ramfs/inode.c
index f8874c3b8c1e..3cc36b1c60b3 100644
--- a/fs/ramfs/inode.c
+++ b/fs/ramfs/inode.c
@@ -110,8 +110,7 @@ ramfs_mknod(struct mnt_idmap *idmap, struct inode *dir,
 			goto out;
 		}
 
-		d_instantiate(dentry, inode);
-		dget(dentry);	/* Extra count - pin the dentry in core */
+		d_make_persistent(dentry, inode);
 		error = 0;
 		inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
 	}
@@ -154,8 +153,7 @@ static int ramfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
 
 		error = page_symlink(inode, symname, l);
 		if (!error) {
-			d_instantiate(dentry, inode);
-			dget(dentry);
+			d_make_persistent(dentry, inode);
 			inode_set_mtime_to_ts(dir,
 					      inode_set_ctime_current(dir));
 		} else
@@ -313,7 +311,7 @@ int ramfs_init_fs_context(struct fs_context *fc)
 void ramfs_kill_sb(struct super_block *sb)
 {
 	kfree(sb->s_fs_info);
-	kill_litter_super(sb);
+	kill_anon_super(sb);
 }
 
 static struct file_system_type ramfs_fs_type = {
diff --git a/init/do_mounts.c b/init/do_mounts.c
index 6af29da8889e..810878fb55b6 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -507,7 +507,7 @@ static int rootfs_init_fs_context(struct fs_context *fc)
 struct file_system_type rootfs_fs_type = {
 	.name		= "rootfs",
 	.init_fs_context = rootfs_init_fs_context,
-	.kill_sb	= kill_litter_super,
+	.kill_sb	= kill_anon_super,
 };
 
 void __init init_rootfs(void)
diff --git a/mm/shmem.c b/mm/shmem.c
index e2c76a30802b..2d5832a1e67a 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -3922,12 +3922,7 @@ shmem_mknod(struct mnt_idmap *idmap, struct inode *dir,
 	inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
 	inode_inc_iversion(dir);
 
-	if (IS_ENABLED(CONFIG_UNICODE) && IS_CASEFOLDED(dir))
-		d_add(dentry, inode);
-	else
-		d_instantiate(dentry, inode);
-
-	dget(dentry); /* Extra count - pin the dentry in core */
+	d_make_persistent(dentry, inode);
 	return error;
 
 out_iput:
@@ -4016,11 +4011,7 @@ static int shmem_link(struct dentry *old_dentry, struct inode *dir,
 	inode_inc_iversion(dir);
 	inc_nlink(inode);
 	ihold(inode);	/* New dentry reference */
-	dget(dentry);	/* Extra pinning count for the created dentry */
-	if (IS_ENABLED(CONFIG_UNICODE) && IS_CASEFOLDED(dir))
-		d_add(dentry, inode);
-	else
-		d_instantiate(dentry, inode);
+	d_make_persistent(dentry, inode);
 out:
 	return ret;
 }
@@ -4039,7 +4030,7 @@ static int shmem_unlink(struct inode *dir, struct dentry *dentry)
 			      inode_set_ctime_to_ts(dir, inode_set_ctime_current(inode)));
 	inode_inc_iversion(dir);
 	drop_nlink(inode);
-	dput(dentry);	/* Undo the count from "create" - does all the work */
+	d_make_discardable(dentry);
 
 	/*
 	 * For now, VFS can't deal with case-insensitive negative dentries, so
@@ -4194,11 +4185,7 @@ static int shmem_symlink(struct mnt_idmap *idmap, struct inode *dir,
 	dir->i_size += BOGO_DIRENT_SIZE;
 	inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
 	inode_inc_iversion(dir);
-	if (IS_ENABLED(CONFIG_UNICODE) && IS_CASEFOLDED(dir))
-		d_add(dentry, inode);
-	else
-		d_instantiate(dentry, inode);
-	dget(dentry);
+	d_make_persistent(dentry, inode);
 	return 0;
 
 out_remove_offset:
@@ -5395,7 +5382,7 @@ static struct file_system_type shmem_fs_type = {
 #ifdef CONFIG_TMPFS
 	.parameters	= shmem_fs_parameters,
 #endif
-	.kill_sb	= kill_litter_super,
+	.kill_sb	= kill_anon_super,
 	.fs_flags	= FS_USERNS_MOUNT | FS_ALLOW_IDMAP | FS_MGTIME,
 };
 
-- 
2.47.3

[PATCH 07/39] procfs: make /self and /thread_self dentries persistent

[Al Viro]

... and there's no need to remember those pointers anywhere - ->kill_sb()
no longer needs to bother since kill_anon_super() will take care of
them anyway and proc_pid_readdir() only wants the inumbers, which
we had in a couple of static variables all along.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/proc/base.c          |  6 ++----
 fs/proc/internal.h      |  1 +
 fs/proc/root.c          | 14 ++++----------
 fs/proc/self.c          | 10 +++-------
 fs/proc/thread_self.c   | 11 +++--------
 include/linux/proc_fs.h |  2 --
 6 files changed, 13 insertions(+), 31 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 62d35631ba8c..f5071b0bdb1b 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -3583,14 +3583,12 @@ int proc_pid_readdir(struct file *file, struct dir_context *ctx)
 		return 0;
 
 	if (pos == TGID_OFFSET - 2) {
-		struct inode *inode = d_inode(fs_info->proc_self);
-		if (!dir_emit(ctx, "self", 4, inode->i_ino, DT_LNK))
+		if (!dir_emit(ctx, "self", 4, self_inum, DT_LNK))
 			return 0;
 		ctx->pos = pos = pos + 1;
 	}
 	if (pos == TGID_OFFSET - 1) {
-		struct inode *inode = d_inode(fs_info->proc_thread_self);
-		if (!dir_emit(ctx, "thread-self", 11, inode->i_ino, DT_LNK))
+		if (!dir_emit(ctx, "thread-self", 11, thread_self_inum, DT_LNK))
 			return 0;
 		ctx->pos = pos = pos + 1;
 	}
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index e737401d7383..e165e406c14d 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -373,6 +373,7 @@ static inline void proc_tty_init(void) {}
 extern struct proc_dir_entry proc_root;
 
 extern void proc_self_init(void);
+extern unsigned self_inum, thread_self_inum;
 
 /*
  * task_[no]mmu.c
diff --git a/fs/proc/root.c b/fs/proc/root.c
index ed86ac710384..7cedc08b92d3 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -261,17 +261,11 @@ static void proc_kill_sb(struct super_block *sb)
 {
 	struct proc_fs_info *fs_info = proc_sb_info(sb);
 
-	if (!fs_info) {
-		kill_anon_super(sb);
-		return;
-	}
-
-	dput(fs_info->proc_self);
-	dput(fs_info->proc_thread_self);
-
 	kill_anon_super(sb);
-	put_pid_ns(fs_info->pid_ns);
-	kfree_rcu(fs_info, rcu);
+	if (fs_info) {
+		put_pid_ns(fs_info->pid_ns);
+		kfree_rcu(fs_info, rcu);
+	}
 }
 
 static struct file_system_type proc_fs_type = {
diff --git a/fs/proc/self.c b/fs/proc/self.c
index b46fbfd22681..62d2c0cfe35c 100644
--- a/fs/proc/self.c
+++ b/fs/proc/self.c
@@ -31,12 +31,11 @@ static const struct inode_operations proc_self_inode_operations = {
 	.get_link	= proc_self_get_link,
 };
 
-static unsigned self_inum __ro_after_init;
+unsigned self_inum __ro_after_init;
 
 int proc_setup_self(struct super_block *s)
 {
 	struct inode *root_inode = d_inode(s->s_root);
-	struct proc_fs_info *fs_info = proc_sb_info(s);
 	struct dentry *self;
 	int ret = -ENOMEM;
 
@@ -51,18 +50,15 @@ int proc_setup_self(struct super_block *s)
 			inode->i_uid = GLOBAL_ROOT_UID;
 			inode->i_gid = GLOBAL_ROOT_GID;
 			inode->i_op = &proc_self_inode_operations;
-			d_add(self, inode);
+			d_make_persistent(self, inode);
 			ret = 0;
-		} else {
-			dput(self);
 		}
+		dput(self);
 	}
 	inode_unlock(root_inode);
 
 	if (ret)
 		pr_err("proc_fill_super: can't allocate /proc/self\n");
-	else
-		fs_info->proc_self = self;
 
 	return ret;
 }
diff --git a/fs/proc/thread_self.c b/fs/proc/thread_self.c
index 0e5050d6ab64..d6113dbe58e0 100644
--- a/fs/proc/thread_self.c
+++ b/fs/proc/thread_self.c
@@ -31,12 +31,11 @@ static const struct inode_operations proc_thread_self_inode_operations = {
 	.get_link	= proc_thread_self_get_link,
 };
 
-static unsigned thread_self_inum __ro_after_init;
+unsigned thread_self_inum __ro_after_init;
 
 int proc_setup_thread_self(struct super_block *s)
 {
 	struct inode *root_inode = d_inode(s->s_root);
-	struct proc_fs_info *fs_info = proc_sb_info(s);
 	struct dentry *thread_self;
 	int ret = -ENOMEM;
 
@@ -51,19 +50,15 @@ int proc_setup_thread_self(struct super_block *s)
 			inode->i_uid = GLOBAL_ROOT_UID;
 			inode->i_gid = GLOBAL_ROOT_GID;
 			inode->i_op = &proc_thread_self_inode_operations;
-			d_add(thread_self, inode);
+			d_make_persistent(thread_self, inode);
 			ret = 0;
-		} else {
-			dput(thread_self);
 		}
+		dput(thread_self);
 	}
 	inode_unlock(root_inode);
 
 	if (ret)
 		pr_err("proc_fill_super: can't allocate /proc/thread-self\n");
-	else
-		fs_info->proc_thread_self = thread_self;
-
 	return ret;
 }
 
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index f139377f4b31..19d1c5e5f335 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -66,8 +66,6 @@ enum proc_pidonly {
 
 struct proc_fs_info {
 	struct pid_namespace *pid_ns;
-	struct dentry *proc_self;        /* For /proc/self */
-	struct dentry *proc_thread_self; /* For /proc/thread-self */
 	kgid_t pid_gid;
 	enum proc_hidepid hide_pid;
 	enum proc_pidonly pidonly;
-- 
2.47.3

[PATCH 08/39] configfs, securityfs: kill_litter_super() not needed

[Al Viro]

These are guaranteed to be empty by the time they are shut down;
both are single-instance and there is an internal mount maintained
for as long as there is any contents.

Both have that internal mount pinned by every object in root.

In other words, kill_litter_super() boils down to kill_anon_super()
for those.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/configfs/mount.c | 2 +-
 security/inode.c    | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/configfs/mount.c b/fs/configfs/mount.c
index 740f18b60c9d..fa66e25f0d75 100644
--- a/fs/configfs/mount.c
+++ b/fs/configfs/mount.c
@@ -116,7 +116,7 @@ static struct file_system_type configfs_fs_type = {
 	.owner		= THIS_MODULE,
 	.name		= "configfs",
 	.init_fs_context = configfs_init_fs_context,
-	.kill_sb	= kill_litter_super,
+	.kill_sb	= kill_anon_super,
 };
 MODULE_ALIAS_FS("configfs");
 
diff --git a/security/inode.c b/security/inode.c
index 43382ef8896e..bf7b5e2e6955 100644
--- a/security/inode.c
+++ b/security/inode.c
@@ -70,7 +70,7 @@ static struct file_system_type fs_type = {
 	.owner =	THIS_MODULE,
 	.name =		"securityfs",
 	.init_fs_context = securityfs_init_fs_context,
-	.kill_sb =	kill_litter_super,
+	.kill_sb =	kill_anon_super,
 };
 
 /**
-- 
2.47.3

Re: [PATCH 08/39] configfs, securityfs: kill_litter_super() not needed

[Joel Becker]

Reviewed-by: Joel Becker <jlbec@evilplan.org>

On Sat, Sep 20, 2025 at 08:47:27AM +0100, Al Viro wrote:
> These are guaranteed to be empty by the time they are shut down;
> both are single-instance and there is an internal mount maintained
> for as long as there is any contents.
> 
> Both have that internal mount pinned by every object in root.
> 
> In other words, kill_litter_super() boils down to kill_anon_super()
> for those.
> 
> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
> ---
>  fs/configfs/mount.c | 2 +-
>  security/inode.c    | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/configfs/mount.c b/fs/configfs/mount.c
> index 740f18b60c9d..fa66e25f0d75 100644
> --- a/fs/configfs/mount.c
> +++ b/fs/configfs/mount.c
> @@ -116,7 +116,7 @@ static struct file_system_type configfs_fs_type = {
>  	.owner		= THIS_MODULE,
>  	.name		= "configfs",
>  	.init_fs_context = configfs_init_fs_context,
> -	.kill_sb	= kill_litter_super,
> +	.kill_sb	= kill_anon_super,
>  };
>  MODULE_ALIAS_FS("configfs");
>  
> diff --git a/security/inode.c b/security/inode.c
> index 43382ef8896e..bf7b5e2e6955 100644
> --- a/security/inode.c
> +++ b/security/inode.c
> @@ -70,7 +70,7 @@ static struct file_system_type fs_type = {
>  	.owner =	THIS_MODULE,
>  	.name =		"securityfs",
>  	.init_fs_context = securityfs_init_fs_context,
> -	.kill_sb =	kill_litter_super,
> +	.kill_sb =	kill_anon_super,
>  };
>  
>  /**
> -- 
> 2.47.3
> 
> 

-- 

The Graham Corollary:

	The longer a socially-moderated news website exists, the
	probability of an old Paul Graham link appearing at the top
	approaches certainty.

			http://www.jlbec.org/
			jlbec@evilplan.org

[PATCH 09/39] convert xenfs

[Al Viro]

entirely static tree, populated by simple_fill_super().  Can switch
to kill_anon_super() without any other changes.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 drivers/xen/xenfs/super.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/xen/xenfs/super.c b/drivers/xen/xenfs/super.c
index d7d64235010d..37ea7c5c0346 100644
--- a/drivers/xen/xenfs/super.c
+++ b/drivers/xen/xenfs/super.c
@@ -88,7 +88,7 @@ static struct file_system_type xenfs_type = {
 	.owner =	THIS_MODULE,
 	.name =		"xenfs",
 	.init_fs_context = xenfs_init_fs_context,
-	.kill_sb =	kill_litter_super,
+	.kill_sb =	kill_anon_super,
 };
 MODULE_ALIAS_FS("xenfs");
 
-- 
2.47.3

[PATCH 10/39] convert smackfs

[Al Viro]

Entirely static tree populated by simple_fill_super().  Can use
kill_anon_super() as-is.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 security/smack/smackfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
index b1e5e62f5cbd..e989ae3890c7 100644
--- a/security/smack/smackfs.c
+++ b/security/smack/smackfs.c
@@ -2960,7 +2960,7 @@ static int smk_init_fs_context(struct fs_context *fc)
 static struct file_system_type smk_fs_type = {
 	.name		= "smackfs",
 	.init_fs_context = smk_init_fs_context,
-	.kill_sb	= kill_litter_super,
+	.kill_sb	= kill_anon_super,
 };
 
 static struct vfsmount *smackfs_mount;
-- 
2.47.3

Re: [PATCH 10/39] convert smackfs

[Casey Schaufler]

On 9/20/2025 12:47 AM, Al Viro wrote:
> Entirely static tree populated by simple_fill_super().  Can use
> kill_anon_super() as-is.
>
> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Looks fine to me.
Acked-by: Casey Schaufler <casey@schaufler-ca.com>

> ---
>  security/smack/smackfs.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
> index b1e5e62f5cbd..e989ae3890c7 100644
> --- a/security/smack/smackfs.c
> +++ b/security/smack/smackfs.c
> @@ -2960,7 +2960,7 @@ static int smk_init_fs_context(struct fs_context *fc)
>  static struct file_system_type smk_fs_type = {
>  	.name		= "smackfs",
>  	.init_fs_context = smk_init_fs_context,
> -	.kill_sb	= kill_litter_super,
> +	.kill_sb	= kill_anon_super,
>  };
>  
>  static struct vfsmount *smackfs_mount;

[PATCH 11/39] convert hugetlbfs

[Al Viro]

Very much ramfs-like; dget()+d_instantiate() -> d_make_persistent()
(in two places) is all it takes.

NB: might make sense to turn its ->put_super() into ->kill_sb().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/hugetlbfs/inode.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 09d4baef29cf..f77fb71f78fc 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -985,8 +985,7 @@ static int hugetlbfs_mknod(struct mnt_idmap *idmap, struct inode *dir,
 	if (!inode)
 		return -ENOSPC;
 	inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
-	d_instantiate(dentry, inode);
-	dget(dentry);/* Extra count - pin the dentry in core */
+	d_make_persistent(dentry, inode);
 	return 0;
 }
 
@@ -1033,10 +1032,9 @@ static int hugetlbfs_symlink(struct mnt_idmap *idmap,
 	if (inode) {
 		int l = strlen(symname)+1;
 		error = page_symlink(inode, symname, l);
-		if (!error) {
-			d_instantiate(dentry, inode);
-			dget(dentry);
-		} else
+		if (!error)
+			d_make_persistent(dentry, inode);
+		else
 			iput(inode);
 	}
 	inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
@@ -1493,7 +1491,7 @@ static struct file_system_type hugetlbfs_fs_type = {
 	.name			= "hugetlbfs",
 	.init_fs_context	= hugetlbfs_init_fs_context,
 	.parameters		= hugetlb_fs_parameters,
-	.kill_sb		= kill_litter_super,
+	.kill_sb		= kill_anon_super,
 	.fs_flags               = FS_ALLOW_IDMAP,
 };
 
-- 
2.47.3

[PATCH 12/39] convert mqueue

[Al Viro]

All modifications via normal VFS codepaths; just take care of making
persistent in in mqueue_create_attr() and discardable in mqueue_unlink()
and it doesn't need kill_litter_super() at all.

mqueue_unlink() side is best handled by having it call simple_unlink()
rather than duplicating its guts...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 ipc/mqueue.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index 093551fe66a7..5737130137bf 100644
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -599,8 +599,7 @@ static int mqueue_create_attr(struct dentry *dentry, umode_t mode, void *arg)
 	dir->i_size += DIRENT_SIZE;
 	simple_inode_init_ts(dir);
 
-	d_instantiate(dentry, inode);
-	dget(dentry);
+	d_make_persistent(dentry, inode);
 	return 0;
 out_unlock:
 	spin_unlock(&mq_lock);
@@ -617,13 +616,8 @@ static int mqueue_create(struct mnt_idmap *idmap, struct inode *dir,
 
 static int mqueue_unlink(struct inode *dir, struct dentry *dentry)
 {
-	struct inode *inode = d_inode(dentry);
-
-	simple_inode_init_ts(dir);
 	dir->i_size -= DIRENT_SIZE;
-	drop_nlink(inode);
-	dput(dentry);
-	return 0;
+	return simple_unlink(dir, dentry);
 }
 
 /*
@@ -1638,7 +1632,7 @@ static const struct fs_context_operations mqueue_fs_context_ops = {
 static struct file_system_type mqueue_fs_type = {
 	.name			= "mqueue",
 	.init_fs_context	= mqueue_init_fs_context,
-	.kill_sb		= kill_litter_super,
+	.kill_sb		= kill_anon_super,
 	.fs_flags		= FS_USERNS_MOUNT,
 };
 
-- 
2.47.3

[PATCH 13/39] convert bpf

[Al Viro]

object creation goes through the normal VFS paths or approximation
thereof (user_path_create()/done_path_create() in case of bpf_obj_do_pin(),
open-coded simple_{start,done}_creating() in bpf_iter_link_pin_kernel()
at mount time), removals go entirely through the normal VFS paths (and
->unlink() is simple_unlink() there).

Enough to have bpf_dentry_finalize() use d_make_persistent() instead
of dget() and we are done.

Convert bpf_iter_link_pin_kernel() to simple_{start,done}_creating(),
while we are at it.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 kernel/bpf/inode.c | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c
index 5c2e96b19392..b9ef1f80ade5 100644
--- a/kernel/bpf/inode.c
+++ b/kernel/bpf/inode.c
@@ -144,8 +144,7 @@ static int bpf_inode_type(const struct inode *inode, enum bpf_type *type)
 static void bpf_dentry_finalize(struct dentry *dentry, struct inode *inode,
 				struct inode *dir)
 {
-	d_instantiate(dentry, inode);
-	dget(dentry);
+	d_make_persistent(dentry, inode);
 
 	inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
 }
@@ -420,16 +419,12 @@ static int bpf_iter_link_pin_kernel(struct dentry *parent,
 	struct dentry *dentry;
 	int ret;
 
-	inode_lock(parent->d_inode);
-	dentry = lookup_noperm(&QSTR(name), parent);
-	if (IS_ERR(dentry)) {
-		inode_unlock(parent->d_inode);
+	dentry = simple_start_creating(parent, name);
+	if (IS_ERR(dentry))
 		return PTR_ERR(dentry);
-	}
 	ret = bpf_mkobj_ops(dentry, mode, link, &bpf_link_iops,
 			    &bpf_iter_fops);
-	dput(dentry);
-	inode_unlock(parent->d_inode);
+	simple_done_creating(dentry);
 	return ret;
 }
 
@@ -1080,7 +1075,7 @@ static void bpf_kill_super(struct super_block *sb)
 {
 	struct bpf_mount_opts *opts = sb->s_fs_info;
 
-	kill_litter_super(sb);
+	kill_anon_super(sb);
 	kfree(opts);
 }
 
-- 
2.47.3

[PATCH 14/39] convert dlmfs

[Al Viro]

All modifications via normal VFS codepaths; just take care of making
persistent in ->create() and ->mkdir() and that's it (removal side
doesn't need any changes, since it uses simple_rmdir() for ->rmdir()
and calls simple_unlink() from ->unlink()).

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/ocfs2/dlmfs/dlmfs.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/fs/ocfs2/dlmfs/dlmfs.c b/fs/ocfs2/dlmfs/dlmfs.c
index 5130ec44e5e1..c1419765a8fb 100644
--- a/fs/ocfs2/dlmfs/dlmfs.c
+++ b/fs/ocfs2/dlmfs/dlmfs.c
@@ -441,8 +441,7 @@ static struct dentry *dlmfs_mkdir(struct mnt_idmap * idmap,
 	ip->ip_conn = conn;
 
 	inc_nlink(dir);
-	d_instantiate(dentry, inode);
-	dget(dentry);	/* Extra count - pin the dentry in core */
+	d_make_persistent(dentry, inode);
 
 	status = 0;
 bail:
@@ -480,8 +479,7 @@ static int dlmfs_create(struct mnt_idmap *idmap,
 		goto bail;
 	}
 
-	d_instantiate(dentry, inode);
-	dget(dentry);	/* Extra count - pin the dentry in core */
+	d_make_persistent(dentry, inode);
 bail:
 	return status;
 }
@@ -574,7 +572,7 @@ static int dlmfs_init_fs_context(struct fs_context *fc)
 static struct file_system_type dlmfs_fs_type = {
 	.owner		= THIS_MODULE,
 	.name		= "ocfs2_dlmfs",
-	.kill_sb	= kill_litter_super,
+	.kill_sb	= kill_anon_super,
 	.init_fs_context = dlmfs_init_fs_context,
 };
 MODULE_ALIAS_FS("ocfs2_dlmfs");
-- 
2.47.3

[PATCH 15/39] convert fuse_ctl

[Al Viro]

objects are created in fuse_ctl_add_dentry() by d_alloc_name()+d_add(),
removed by simple_remove_by_name().

What we return is a borrowed reference - it is valid until the call of
fuse_ctl_remove_conn() and we depend upon the exclusion (on fuse_mutex)
for safety.  Return value is used only within the caller
(fuse_ctl_add_conn()).

Replace d_add() with d_make_persistent() + dput().  dput() is paired
with d_alloc_name() and return value is the result of d_make_persistent().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/fuse/control.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/fs/fuse/control.c b/fs/fuse/control.c
index 31fa816d0189..adcb81e04802 100644
--- a/fs/fuse/control.c
+++ b/fs/fuse/control.c
@@ -234,8 +234,14 @@ static struct dentry *fuse_ctl_add_dentry(struct dentry *parent,
 	inode->i_fop = fop;
 	set_nlink(inode, nlink);
 	inode->i_private = fc;
-	d_add(dentry, inode);
-
+	d_make_persistent(dentry, inode);
+	dput(dentry);
+
+	/*
+	 * We are returning a borrowed reference here - it's only good while
+	 * fuse_mutex is held.  Actually it's d_make_persistent() return
+	 * value...
+	 */
 	return dentry;
 }
 
@@ -345,7 +351,7 @@ static void fuse_ctl_kill_sb(struct super_block *sb)
 	fuse_control_sb = NULL;
 	mutex_unlock(&fuse_mutex);
 
-	kill_litter_super(sb);
+	kill_anon_super(sb);
 }
 
 static struct file_system_type fuse_ctl_fs_type = {
-- 
2.47.3

[PATCH 16/39] convert pstore

[Al Viro]

object creation by d_alloc_name()+d_add() in pstore_mkfile(), removal -
via normal VFS codepaths (with ->unlink() using simple_unlink()) or
in pstore_put_backend_records() via locked_recursive_removal()

Replace d_add() with d_make_persistent()+dput() - that's what really
happens there.  The reference that goes into record->dentry is valid
only until the unlink (and explicitly cleared by pstore_unlink()).

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/pstore/inode.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
index 1a2e1185426c..bad479fbb0ff 100644
--- a/fs/pstore/inode.c
+++ b/fs/pstore/inode.c
@@ -373,7 +373,7 @@ int pstore_mkfile(struct dentry *root, struct pstore_record *record)
 	if (!dentry)
 		return -ENOMEM;
 
-	private->dentry = dentry;
+	private->dentry = dentry; // borrowed
 	private->record = record;
 	inode->i_size = private->total_size = size;
 	inode->i_private = private;
@@ -382,7 +382,8 @@ int pstore_mkfile(struct dentry *root, struct pstore_record *record)
 		inode_set_mtime_to_ts(inode,
 				      inode_set_ctime_to_ts(inode, record->time));
 
-	d_add(dentry, no_free_ptr(inode));
+	d_make_persistent(dentry, no_free_ptr(inode));
+	dput(dentry);
 
 	list_add(&(no_free_ptr(private))->list, &records_list);
 
@@ -465,7 +466,7 @@ static void pstore_kill_sb(struct super_block *sb)
 	guard(mutex)(&pstore_sb_lock);
 	WARN_ON(pstore_sb && pstore_sb != sb);
 
-	kill_litter_super(sb);
+	kill_anon_super(sb);
 	pstore_sb = NULL;
 
 	guard(mutex)(&records_list_lock);
-- 
2.47.3

[PATCH 17/39] convert tracefs

[Al Viro]

A mix of persistent and non-persistent dentries in there.  Strictly
speaking, no need for kill_litter_super() anyway - it pins an internal
mount whenever a persistent dentry is created, so at fs shutdown time
there won't be any to deal with.

However, let's make it explicit - replace d_instantiate() with
d_make_persistent() + dput() (the latter in tracefs_end_creating())
for dentries we want persistent and have d_make_discardable() done
either by simple_recursive_removal() (used by tracefs_remove())
or explicitly in eventfs_remove_events_dir().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/tracefs/event_inode.c |  4 ++--
 fs/tracefs/inode.c       | 13 ++++++-------
 2 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index 8705c77a9e75..97bb0a79b0cd 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -822,7 +822,7 @@ struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry
 	 * something not worth much. Keeping directory links at 1
 	 * tells userspace not to trust the link number.
 	 */
-	d_instantiate(dentry, inode);
+	d_make_persistent(dentry, inode);
 	/* The dentry of the "events" parent does keep track though */
 	inc_nlink(dentry->d_parent->d_inode);
 	fsnotify_mkdir(dentry->d_parent->d_inode, dentry);
@@ -909,5 +909,5 @@ void eventfs_remove_events_dir(struct eventfs_inode *ei)
 	 * and destroyed dynamically.
 	 */
 	d_invalidate(dentry);
-	dput(dentry);
+	d_make_discardable(dentry);
 }
diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index 0c023941a316..d9d8932a7b9c 100644
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -538,7 +538,7 @@ static struct file_system_type trace_fs_type = {
 	.name =		"tracefs",
 	.init_fs_context = tracefs_init_fs_context,
 	.parameters	= tracefs_param_specs,
-	.kill_sb =	kill_litter_super,
+	.kill_sb =	kill_anon_super,
 };
 MODULE_ALIAS_FS("tracefs");
 
@@ -571,16 +571,15 @@ struct dentry *tracefs_start_creating(const char *name, struct dentry *parent)
 
 struct dentry *tracefs_failed_creating(struct dentry *dentry)
 {
-	inode_unlock(d_inode(dentry->d_parent));
-	dput(dentry);
+	simple_done_creating(dentry);
 	simple_release_fs(&tracefs_mount, &tracefs_mount_count);
 	return NULL;
 }
 
 struct dentry *tracefs_end_creating(struct dentry *dentry)
 {
-	inode_unlock(d_inode(dentry->d_parent));
-	return dentry;
+	simple_done_creating(dentry);
+	return dentry;	// borrowed
 }
 
 /* Find the inode that this will use for default */
@@ -661,7 +660,7 @@ struct dentry *tracefs_create_file(const char *name, umode_t mode,
 	inode->i_private = data;
 	inode->i_uid = d_inode(dentry->d_parent)->i_uid;
 	inode->i_gid = d_inode(dentry->d_parent)->i_gid;
-	d_instantiate(dentry, inode);
+	d_make_persistent(dentry, inode);
 	fsnotify_create(d_inode(dentry->d_parent), dentry);
 	return tracefs_end_creating(dentry);
 }
@@ -692,7 +691,7 @@ static struct dentry *__create_dir(const char *name, struct dentry *parent,
 
 	/* directory inodes start off with i_nlink == 2 (for "." entry) */
 	inc_nlink(inode);
-	d_instantiate(dentry, inode);
+	d_make_persistent(dentry, inode);
 	inc_nlink(d_inode(dentry->d_parent));
 	fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
 	return tracefs_end_creating(dentry);
-- 
2.47.3

[PATCH 18/39] convert debugfs

[Al Viro]

similar to tracefs - simulation of normal codepath for creation,
simple_recursive_removal() for removal.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/debugfs/inode.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index c12d649df6a5..1302995d6816 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -329,7 +329,7 @@ static struct file_system_type debug_fs_type = {
 	.name =		"debugfs",
 	.init_fs_context = debugfs_init_fs_context,
 	.parameters =	debugfs_param_specs,
-	.kill_sb =	kill_litter_super,
+	.kill_sb =	kill_anon_super,
 };
 MODULE_ALIAS_FS("debugfs");
 
@@ -404,16 +404,15 @@ static struct dentry *start_creating(const char *name, struct dentry *parent)
 
 static struct dentry *failed_creating(struct dentry *dentry)
 {
-	inode_unlock(d_inode(dentry->d_parent));
-	dput(dentry);
+	simple_done_creating(dentry);
 	simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 	return ERR_PTR(-ENOMEM);
 }
 
 static struct dentry *end_creating(struct dentry *dentry)
 {
-	inode_unlock(d_inode(dentry->d_parent));
-	return dentry;
+	simple_done_creating(dentry);
+	return dentry; // borrowed
 }
 
 static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
@@ -455,7 +454,7 @@ static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
 	DEBUGFS_I(inode)->raw = real_fops;
 	DEBUGFS_I(inode)->aux = (void *)aux;
 
-	d_instantiate(dentry, inode);
+	d_make_persistent(dentry, inode);
 	fsnotify_create(d_inode(dentry->d_parent), dentry);
 	return end_creating(dentry);
 }
@@ -601,7 +600,7 @@ struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
 
 	/* directory inodes start off with i_nlink == 2 (for "." entry) */
 	inc_nlink(inode);
-	d_instantiate(dentry, inode);
+	d_make_persistent(dentry, inode);
 	inc_nlink(d_inode(dentry->d_parent));
 	fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
 	return end_creating(dentry);
@@ -648,7 +647,7 @@ struct dentry *debugfs_create_automount(const char *name,
 	DEBUGFS_I(inode)->automount = f;
 	/* directory inodes start off with i_nlink == 2 (for "." entry) */
 	inc_nlink(inode);
-	d_instantiate(dentry, inode);
+	d_make_persistent(dentry, inode);
 	inc_nlink(d_inode(dentry->d_parent));
 	fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
 	return end_creating(dentry);
@@ -703,7 +702,7 @@ struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
 	inode->i_mode = S_IFLNK | S_IRWXUGO;
 	inode->i_op = &debugfs_symlink_inode_operations;
 	inode->i_link = link;
-	d_instantiate(dentry, inode);
+	d_make_persistent(dentry, inode);
 	return end_creating(dentry);
 }
 EXPORT_SYMBOL_GPL(debugfs_create_symlink);
-- 
2.47.3

Re: [PATCH 18/39] convert debugfs

[Greg KH]

On Sat, Sep 20, 2025 at 08:47:37AM +0100, Al Viro wrote:
> similar to tracefs - simulation of normal codepath for creation,
> simple_recursive_removal() for removal.
> 
> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
> ---
>  fs/debugfs/inode.c | 17 ++++++++---------
>  1 file changed, 8 insertions(+), 9 deletions(-)

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

[PATCH 19/39] debugfs: remove duplicate checks in callers of start_creating()

[Al Viro]

we'd already verified that DEBUGFS_ALLOW_API was there in
start_creating() - it would've failed otherwise

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/debugfs/inode.c | 15 ---------------
 1 file changed, 15 deletions(-)

diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index 1302995d6816..95eb57566d26 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -432,11 +432,6 @@ static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
 	if (IS_ERR(dentry))
 		return dentry;
 
-	if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
-		failed_creating(dentry);
-		return ERR_PTR(-EPERM);
-	}
-
 	inode = debugfs_get_inode(dentry->d_sb);
 	if (unlikely(!inode)) {
 		pr_err("out of free dentries, can not create file '%s'\n",
@@ -582,11 +577,6 @@ struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
 	if (IS_ERR(dentry))
 		return dentry;
 
-	if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
-		failed_creating(dentry);
-		return ERR_PTR(-EPERM);
-	}
-
 	inode = debugfs_get_inode(dentry->d_sb);
 	if (unlikely(!inode)) {
 		pr_err("out of free dentries, can not create directory '%s'\n",
@@ -629,11 +619,6 @@ struct dentry *debugfs_create_automount(const char *name,
 	if (IS_ERR(dentry))
 		return dentry;
 
-	if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
-		failed_creating(dentry);
-		return ERR_PTR(-EPERM);
-	}
-
 	inode = debugfs_get_inode(dentry->d_sb);
 	if (unlikely(!inode)) {
 		pr_err("out of free dentries, can not create automount '%s'\n",
-- 
2.47.3

Re: [PATCH 19/39] debugfs: remove duplicate checks in callers of start_creating()

[Greg KH]

On Sat, Sep 20, 2025 at 08:47:38AM +0100, Al Viro wrote:
> we'd already verified that DEBUGFS_ALLOW_API was there in
> start_creating() - it would've failed otherwise
> 
> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
> ---
>  fs/debugfs/inode.c | 15 ---------------
>  1 file changed, 15 deletions(-)

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

[PATCH 20/39] convert efivarfs

[Al Viro]

Initially filesystem is populated with d_alloc_name() + d_add().
That becomes d_alloc_name() + d_make_persistent() + dput().
Dynamic creation is switched to d_make_persistent();
removal - to simple_unlink() (no point open-coding it in
efivarfs_unlink(), better call it there)

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/efivarfs/inode.c | 7 ++-----
 fs/efivarfs/super.c | 5 +++--
 2 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/fs/efivarfs/inode.c b/fs/efivarfs/inode.c
index 2891614abf8d..95dcad83da11 100644
--- a/fs/efivarfs/inode.c
+++ b/fs/efivarfs/inode.c
@@ -113,8 +113,7 @@ static int efivarfs_create(struct mnt_idmap *idmap, struct inode *dir,
 
 	inode->i_private = var;
 
-	d_instantiate(dentry, inode);
-	dget(dentry);
+	d_make_persistent(dentry, inode);
 
 	return 0;
 }
@@ -126,9 +125,7 @@ static int efivarfs_unlink(struct inode *dir, struct dentry *dentry)
 	if (efivar_entry_delete(var))
 		return -EINVAL;
 
-	drop_nlink(d_inode(dentry));
-	dput(dentry);
-	return 0;
+	return simple_unlink(dir, dentry);
 };
 
 const struct inode_operations efivarfs_dir_inode_operations = {
diff --git a/fs/efivarfs/super.c b/fs/efivarfs/super.c
index 4bb4002e3cdf..21208660bfe2 100644
--- a/fs/efivarfs/super.c
+++ b/fs/efivarfs/super.c
@@ -278,7 +278,8 @@ static int efivarfs_create_dentry(struct super_block *sb, efi_char16_t *name16,
 	inode->i_private = entry;
 	i_size_write(inode, size + sizeof(__u32)); /* attributes + data */
 	inode_unlock(inode);
-	d_add(dentry, inode);
+	d_make_persistent(dentry, inode);
+	dput(dentry);
 
 	return 0;
 
@@ -522,7 +523,7 @@ static void efivarfs_kill_sb(struct super_block *sb)
 	struct efivarfs_fs_info *sfi = sb->s_fs_info;
 
 	blocking_notifier_chain_unregister(&efivar_ops_nh, &sfi->nb);
-	kill_litter_super(sb);
+	kill_anon_super(sb);
 
 	kfree(sfi);
 }
-- 
2.47.3

[PATCH 21/39] convert spufs

[Al Viro]

have spufs_new_file() use d_make_persistent() instead of d_add() and
do an uncondition dput() in the caller; the rest is completely
straightforward.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 arch/powerpc/platforms/cell/spufs/inode.c | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/arch/powerpc/platforms/cell/spufs/inode.c b/arch/powerpc/platforms/cell/spufs/inode.c
index 7ec60290abe6..f21f7a76ef0b 100644
--- a/arch/powerpc/platforms/cell/spufs/inode.c
+++ b/arch/powerpc/platforms/cell/spufs/inode.c
@@ -127,7 +127,7 @@ spufs_new_file(struct super_block *sb, struct dentry *dentry,
 	inode->i_fop = fops;
 	inode->i_size = size;
 	inode->i_private = SPUFS_I(inode)->i_ctx = get_spu_context(ctx);
-	d_add(dentry, inode);
+	d_make_persistent(dentry, inode);
 out:
 	return ret;
 }
@@ -163,10 +163,9 @@ static int spufs_fill_dir(struct dentry *dir,
 			return -ENOMEM;
 		ret = spufs_new_file(dir->d_sb, dentry, files->ops,
 					files->mode & mode, files->size, ctx);
-		if (ret) {
-			dput(dentry);
+		dput(dentry);
+		if (ret)
 			return ret;
-		}
 		files++;
 	}
 	return 0;
@@ -241,11 +240,10 @@ spufs_mkdir(struct inode *dir, struct dentry *dentry, unsigned int flags,
 
 	inode_lock(inode);
 
-	dget(dentry);
 	inc_nlink(dir);
 	inc_nlink(inode);
 
-	d_instantiate(dentry, inode);
+	d_make_persistent(dentry, inode);
 
 	if (flags & SPU_CREATE_NOSCHED)
 		ret = spufs_fill_dir(dentry, spufs_dir_nosched_contents,
@@ -479,10 +477,9 @@ spufs_mkgang(struct inode *dir, struct dentry *dentry, umode_t mode)
 	inode->i_op = &simple_dir_inode_operations;
 	inode->i_fop = &simple_dir_operations;
 
-	d_instantiate(dentry, inode);
-	dget(dentry);
 	inc_nlink(dir);
 	inc_nlink(d_inode(dentry));
+	d_make_persistent(dentry, inode);
 	return ret;
 
 out_iput:
@@ -780,7 +777,7 @@ static struct file_system_type spufs_type = {
 	.name = "spufs",
 	.init_fs_context = spufs_init_fs_context,
 	.parameters	= spufs_fs_parameters,
-	.kill_sb = kill_litter_super,
+	.kill_sb = kill_anon_super,
 };
 MODULE_ALIAS_FS("spufs");
 
-- 
2.47.3

[PATCH 22/39] convert ibmasmfs

[Al Viro]

static contents for each "service processor", whatever the fuck it is.
Congruent subdirectories of root, created at mount time, taken out
by kill_litter_super().  All dentries created with d_alloc_name() and are
left pinned.  The odd part is that the list of service providers is
assumed to be unchanging - no locking, nothing to handle removals or
extra elements added later on.

... and it's a PCI device.  If you ever tell it to remove an instance,
you are fucked - it doesn't bother with removing its directory from filesystem,
it has a strange check that presumably wanted to be a check for removed
devices, but it had never been fleshed out.

Anyway, d_add() -> d_make_persistent()+dput() in ibmasmfs_create_dir() and
ibmasmfs_create_file(), and make the latter return int - no need to even
borrow that dentry, callers completely ignore it.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 drivers/misc/ibmasm/ibmasmfs.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/misc/ibmasm/ibmasmfs.c b/drivers/misc/ibmasm/ibmasmfs.c
index c44de892a61e..785ce294f4b9 100644
--- a/drivers/misc/ibmasm/ibmasmfs.c
+++ b/drivers/misc/ibmasm/ibmasmfs.c
@@ -103,7 +103,7 @@ static struct file_system_type ibmasmfs_type = {
 	.owner          = THIS_MODULE,
 	.name           = "ibmasmfs",
 	.init_fs_context = ibmasmfs_init_fs_context,
-	.kill_sb        = kill_litter_super,
+	.kill_sb        = kill_anon_super,
 };
 MODULE_ALIAS_FS("ibmasmfs");
 
@@ -144,7 +144,7 @@ static struct inode *ibmasmfs_make_inode(struct super_block *sb, int mode)
 	return ret;
 }
 
-static struct dentry *ibmasmfs_create_file(struct dentry *parent,
+static int ibmasmfs_create_file(struct dentry *parent,
 			const char *name,
 			const struct file_operations *fops,
 			void *data,
@@ -155,19 +155,20 @@ static struct dentry *ibmasmfs_create_file(struct dentry *parent,
 
 	dentry = d_alloc_name(parent, name);
 	if (!dentry)
-		return NULL;
+		return -ENOMEM;
 
 	inode = ibmasmfs_make_inode(parent->d_sb, S_IFREG | mode);
 	if (!inode) {
 		dput(dentry);
-		return NULL;
+		return -ENOMEM;
 	}
 
 	inode->i_fop = fops;
 	inode->i_private = data;
 
-	d_add(dentry, inode);
-	return dentry;
+	d_make_persistent(dentry, inode);
+	dput(dentry);
+	return 0;
 }
 
 static struct dentry *ibmasmfs_create_dir(struct dentry *parent,
@@ -189,8 +190,9 @@ static struct dentry *ibmasmfs_create_dir(struct dentry *parent,
 	inode->i_op = &simple_dir_inode_operations;
 	inode->i_fop = ibmasmfs_dir_ops;
 
-	d_add(dentry, inode);
-	return dentry;
+	d_make_persistent(dentry, inode);
+	dput(dentry);
+	return dentry; // borrowed
 }
 
 int ibmasmfs_register(void)
-- 
2.47.3

[PATCH 23/39] ibmasmfs: get rid of ibmasmfs_dir_ops

[Al Viro]

it is always equal (and always had been equal) to &simple_dir_operations

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 drivers/misc/ibmasm/ibmasmfs.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/misc/ibmasm/ibmasmfs.c b/drivers/misc/ibmasm/ibmasmfs.c
index 785ce294f4b9..7427adff2a62 100644
--- a/drivers/misc/ibmasm/ibmasmfs.c
+++ b/drivers/misc/ibmasm/ibmasmfs.c
@@ -97,8 +97,6 @@ static const struct super_operations ibmasmfs_s_ops = {
 	.drop_inode	= generic_delete_inode,
 };
 
-static const struct file_operations *ibmasmfs_dir_ops = &simple_dir_operations;
-
 static struct file_system_type ibmasmfs_type = {
 	.owner          = THIS_MODULE,
 	.name           = "ibmasmfs",
@@ -122,7 +120,7 @@ static int ibmasmfs_fill_super(struct super_block *sb, struct fs_context *fc)
 		return -ENOMEM;
 
 	root->i_op = &simple_dir_inode_operations;
-	root->i_fop = ibmasmfs_dir_ops;
+	root->i_fop = &simple_dir_operations;
 
 	sb->s_root = d_make_root(root);
 	if (!sb->s_root)
@@ -188,7 +186,7 @@ static struct dentry *ibmasmfs_create_dir(struct dentry *parent,
 	}
 
 	inode->i_op = &simple_dir_inode_operations;
-	inode->i_fop = ibmasmfs_dir_ops;
+	inode->i_fop = &simple_dir_operations;
 
 	d_make_persistent(dentry, inode);
 	dput(dentry);
-- 
2.47.3

[PATCH 24/39] convert devpts

[Al Viro]

Two kinds of objects there - ptmx and everything else (pty).  The former is
created on mount and kept until the fs shutdown; the latter get created
and removed by tty layer (the references are borrowed into tty->driver_data).
The reference to ptmx dentry is also kept, but we only ever use it to
find ptmx inode on remount.

* turn d_add() into d_make_persistent() + dput()  both in mknod_ptmx() and
in devpts_pty_new().

* turn dput() to d_make_discardable() in devpts_pty_kill().

* switch mknod_ptmx() to simple_{start,done}_creating().

* instead of storing a reference to ptmx dentry pts_fs_info, store a reference
to its inode, seeing that this is what we use it for.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/devpts/inode.c | 57 +++++++++++++++++------------------------------
 1 file changed, 21 insertions(+), 36 deletions(-)

diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c
index fdf22264a8e9..9f3de528c358 100644
--- a/fs/devpts/inode.c
+++ b/fs/devpts/inode.c
@@ -102,7 +102,7 @@ struct pts_fs_info {
 	struct ida allocated_ptys;
 	struct pts_mount_opts mount_opts;
 	struct super_block *sb;
-	struct dentry *ptmx_dentry;
+	struct inode *ptmx_inode; // borrowed
 };
 
 static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb)
@@ -259,7 +259,6 @@ static int devpts_parse_param(struct fs_context *fc, struct fs_parameter *param)
 static int mknod_ptmx(struct super_block *sb, struct fs_context *fc)
 {
 	int mode;
-	int rc = -ENOMEM;
 	struct dentry *dentry;
 	struct inode *inode;
 	struct dentry *root = sb->s_root;
@@ -268,18 +267,10 @@ static int mknod_ptmx(struct super_block *sb, struct fs_context *fc)
 	kuid_t ptmx_uid = current_fsuid();
 	kgid_t ptmx_gid = current_fsgid();
 
-	inode_lock(d_inode(root));
-
-	/* If we have already created ptmx node, return */
-	if (fsi->ptmx_dentry) {
-		rc = 0;
-		goto out;
-	}
-
-	dentry = d_alloc_name(root, "ptmx");
-	if (!dentry) {
+	dentry = simple_start_creating(root, "ptmx");
+	if (IS_ERR(dentry)) {
 		pr_err("Unable to alloc dentry for ptmx node\n");
-		goto out;
+		return PTR_ERR(dentry);
 	}
 
 	/*
@@ -287,9 +278,9 @@ static int mknod_ptmx(struct super_block *sb, struct fs_context *fc)
 	 */
 	inode = new_inode(sb);
 	if (!inode) {
+		simple_done_creating(dentry);
 		pr_err("Unable to alloc inode for ptmx node\n");
-		dput(dentry);
-		goto out;
+		return -ENOMEM;
 	}
 
 	inode->i_ino = 2;
@@ -299,23 +290,18 @@ static int mknod_ptmx(struct super_block *sb, struct fs_context *fc)
 	init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2));
 	inode->i_uid = ptmx_uid;
 	inode->i_gid = ptmx_gid;
+	fsi->ptmx_inode = inode;
 
-	d_add(dentry, inode);
+	d_make_persistent(dentry, inode);
 
-	fsi->ptmx_dentry = dentry;
-	rc = 0;
-out:
-	inode_unlock(d_inode(root));
-	return rc;
+	simple_done_creating(dentry);
+
+	return 0;
 }
 
 static void update_ptmx_mode(struct pts_fs_info *fsi)
 {
-	struct inode *inode;
-	if (fsi->ptmx_dentry) {
-		inode = d_inode(fsi->ptmx_dentry);
-		inode->i_mode = S_IFCHR|fsi->mount_opts.ptmxmode;
-	}
+	fsi->ptmx_inode->i_mode = S_IFCHR|fsi->mount_opts.ptmxmode;
 }
 
 static int devpts_reconfigure(struct fs_context *fc)
@@ -461,7 +447,7 @@ static void devpts_kill_sb(struct super_block *sb)
 	if (fsi)
 		ida_destroy(&fsi->allocated_ptys);
 	kfree(fsi);
-	kill_litter_super(sb);
+	kill_anon_super(sb);
 }
 
 static struct file_system_type devpts_fs_type = {
@@ -534,16 +520,15 @@ struct dentry *devpts_pty_new(struct pts_fs_info *fsi, int index, void *priv)
 	sprintf(s, "%d", index);
 
 	dentry = d_alloc_name(root, s);
-	if (dentry) {
-		dentry->d_fsdata = priv;
-		d_add(dentry, inode);
-		fsnotify_create(d_inode(root), dentry);
-	} else {
+	if (!dentry) {
 		iput(inode);
-		dentry = ERR_PTR(-ENOMEM);
+		return ERR_PTR(-ENOMEM);
 	}
-
-	return dentry;
+	dentry->d_fsdata = priv;
+	d_make_persistent(dentry, inode);
+	fsnotify_create(d_inode(root), dentry);
+	dput(dentry);
+	return dentry; // borrowed
 }
 
 /**
@@ -573,7 +558,7 @@ void devpts_pty_kill(struct dentry *dentry)
 	drop_nlink(dentry->d_inode);
 	d_drop(dentry);
 	fsnotify_unlink(d_inode(dentry->d_parent), dentry);
-	dput(dentry);	/* d_alloc_name() in devpts_pty_new() */
+	d_make_discardable(dentry);
 }
 
 static int __init init_devpts_fs(void)
-- 
2.47.3

[PATCH 25/39] binderfs: use simple_start_creating()

[Al Viro]

binderfs_binder_device_create() gets simpler, binderfs_create_dentry() simply
goes away...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 drivers/android/binderfs.c | 43 +++++---------------------------------
 1 file changed, 5 insertions(+), 38 deletions(-)

diff --git a/drivers/android/binderfs.c b/drivers/android/binderfs.c
index 0d9d95a7fb60..41a0f3c26fcf 100644
--- a/drivers/android/binderfs.c
+++ b/drivers/android/binderfs.c
@@ -181,24 +181,11 @@ static int binderfs_binder_device_create(struct inode *ref_inode,
 	}
 
 	root = sb->s_root;
-	inode_lock(d_inode(root));
-
-	/* look it up */
-	dentry = lookup_noperm(&QSTR(name), root);
+	dentry = simple_start_creating(root, name);
 	if (IS_ERR(dentry)) {
-		inode_unlock(d_inode(root));
 		ret = PTR_ERR(dentry);
 		goto err;
 	}
-
-	if (d_really_is_positive(dentry)) {
-		/* already exists */
-		dput(dentry);
-		inode_unlock(d_inode(root));
-		ret = -EEXIST;
-		goto err;
-	}
-
 	inode->i_private = device;
 	d_instantiate(dentry, inode);
 	fsnotify_create(root->d_inode, dentry);
@@ -479,24 +466,6 @@ static struct inode *binderfs_make_inode(struct super_block *sb, int mode)
 	return ret;
 }
 
-static struct dentry *binderfs_create_dentry(struct dentry *parent,
-					     const char *name)
-{
-	struct dentry *dentry;
-
-	dentry = lookup_noperm(&QSTR(name), parent);
-	if (IS_ERR(dentry))
-		return dentry;
-
-	/* Return error if the file/dir already exists. */
-	if (d_really_is_positive(dentry)) {
-		dput(dentry);
-		return ERR_PTR(-EEXIST);
-	}
-
-	return dentry;
-}
-
 struct dentry *binderfs_create_file(struct dentry *parent, const char *name,
 				    const struct file_operations *fops,
 				    void *data)
@@ -506,11 +475,10 @@ struct dentry *binderfs_create_file(struct dentry *parent, const char *name,
 	struct super_block *sb;
 
 	parent_inode = d_inode(parent);
-	inode_lock(parent_inode);
 
-	dentry = binderfs_create_dentry(parent, name);
+	dentry = simple_start_creating(parent, name);
 	if (IS_ERR(dentry))
-		goto out;
+		return dentry;
 
 	sb = parent_inode->i_sb;
 	new_inode = binderfs_make_inode(sb, S_IFREG | 0444);
@@ -538,11 +506,10 @@ static struct dentry *binderfs_create_dir(struct dentry *parent,
 	struct super_block *sb;
 
 	parent_inode = d_inode(parent);
-	inode_lock(parent_inode);
 
-	dentry = binderfs_create_dentry(parent, name);
+	dentry = simple_start_creating(parent, name);
 	if (IS_ERR(dentry))
-		goto out;
+		return dentry;
 
 	sb = parent_inode->i_sb;
 	new_inode = binderfs_make_inode(sb, S_IFDIR | 0755);
-- 
2.47.3

[PATCH 26/39] binderfs_binder_ctl_create(): kill a bogus check

[Al Viro]

It's called once, during binderfs mount, right after allocating
root dentry.  Checking that it hadn't been already called is
only obfuscating things.

Looks like that bogosity had been copied from devpts...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 drivers/android/binderfs.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/drivers/android/binderfs.c b/drivers/android/binderfs.c
index 41a0f3c26fcf..bb81280a3e9f 100644
--- a/drivers/android/binderfs.c
+++ b/drivers/android/binderfs.c
@@ -395,12 +395,6 @@ static int binderfs_binder_ctl_create(struct super_block *sb)
 	if (!device)
 		return -ENOMEM;
 
-	/* If we have already created a binder-control node, return. */
-	if (info->control_dentry) {
-		ret = 0;
-		goto out;
-	}
-
 	ret = -ENOMEM;
 	inode = new_inode(sb);
 	if (!inode)
-- 
2.47.3

[PATCH 27/39] convert binderfs

[Al Viro]

Objects are created either by d_alloc_name()+d_add() (in
binderfs_ctl_create()) or by simple_start_creating()+d_instantiate().
Removals are by simple_recurisive_removal().

Switch d_add()/d_instantiate() to d_make_persistent() + dput().
Voila - kill_litter_super() is not needed anymore.

Fold dput()+unlocking the parent into simple_done_creating(), while
we are at it.

NOTE: return value of binderfs_create_file() is borrowed; it may get
stored in proc->binderfs_entry.  See binder_release()...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 drivers/android/binderfs.c | 33 ++++++++++++++-------------------
 1 file changed, 14 insertions(+), 19 deletions(-)

diff --git a/drivers/android/binderfs.c b/drivers/android/binderfs.c
index bb81280a3e9f..20c5b34fc775 100644
--- a/drivers/android/binderfs.c
+++ b/drivers/android/binderfs.c
@@ -187,9 +187,9 @@ static int binderfs_binder_device_create(struct inode *ref_inode,
 		goto err;
 	}
 	inode->i_private = device;
-	d_instantiate(dentry, inode);
+	d_make_persistent(dentry, inode);
 	fsnotify_create(root->d_inode, dentry);
-	inode_unlock(d_inode(root));
+	simple_done_creating(dentry);
 
 	binder_add_device(device);
 
@@ -430,7 +430,8 @@ static int binderfs_binder_ctl_create(struct super_block *sb)
 
 	inode->i_private = device;
 	info->control_dentry = dentry;
-	d_add(dentry, inode);
+	d_make_persistent(dentry, inode);
+	dput(dentry);
 
 	return 0;
 
@@ -477,19 +478,16 @@ struct dentry *binderfs_create_file(struct dentry *parent, const char *name,
 	sb = parent_inode->i_sb;
 	new_inode = binderfs_make_inode(sb, S_IFREG | 0444);
 	if (!new_inode) {
-		dput(dentry);
-		dentry = ERR_PTR(-ENOMEM);
-		goto out;
+		simple_done_creating(dentry);
+		return ERR_PTR(-ENOMEM);
 	}
 
 	new_inode->i_fop = fops;
 	new_inode->i_private = data;
-	d_instantiate(dentry, new_inode);
+	d_make_persistent(dentry, new_inode);
 	fsnotify_create(parent_inode, dentry);
-
-out:
-	inode_unlock(parent_inode);
-	return dentry;
+	simple_done_creating(dentry);
+	return dentry; // borrowed
 }
 
 static struct dentry *binderfs_create_dir(struct dentry *parent,
@@ -508,21 +506,18 @@ static struct dentry *binderfs_create_dir(struct dentry *parent,
 	sb = parent_inode->i_sb;
 	new_inode = binderfs_make_inode(sb, S_IFDIR | 0755);
 	if (!new_inode) {
-		dput(dentry);
-		dentry = ERR_PTR(-ENOMEM);
-		goto out;
+		simple_done_creating(dentry);
+		return ERR_PTR(-ENOMEM);
 	}
 
 	new_inode->i_fop = &simple_dir_operations;
 	new_inode->i_op = &simple_dir_inode_operations;
 
 	set_nlink(new_inode, 2);
-	d_instantiate(dentry, new_inode);
+	d_make_persistent(dentry, new_inode);
 	inc_nlink(parent_inode);
 	fsnotify_mkdir(parent_inode, dentry);
-
-out:
-	inode_unlock(parent_inode);
+	simple_done_creating(dentry);
 	return dentry;
 }
 
@@ -732,7 +727,7 @@ static void binderfs_kill_super(struct super_block *sb)
 	 * During inode eviction struct binderfs_info is needed.
 	 * So first wipe the super_block then free struct binderfs_info.
 	 */
-	kill_litter_super(sb);
+	kill_anon_super(sb);
 
 	if (info && info->ipc_ns)
 		put_ipc_ns(info->ipc_ns);
-- 
2.47.3

[PATCH 28/39] autofs_{rmdir,unlink}: dentry->d_fsdata->dentry == dentry there

[Al Viro]

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/autofs/root.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/fs/autofs/root.c b/fs/autofs/root.c
index 174c7205fee4..39794633d484 100644
--- a/fs/autofs/root.c
+++ b/fs/autofs/root.c
@@ -623,12 +623,11 @@ static int autofs_dir_symlink(struct mnt_idmap *idmap,
 static int autofs_dir_unlink(struct inode *dir, struct dentry *dentry)
 {
 	struct autofs_sb_info *sbi = autofs_sbi(dir->i_sb);
-	struct autofs_info *ino = autofs_dentry_ino(dentry);
 	struct autofs_info *p_ino;
 
 	p_ino = autofs_dentry_ino(dentry->d_parent);
 	p_ino->count--;
-	dput(ino->dentry);
+	dput(dentry);
 
 	d_inode(dentry)->i_size = 0;
 	clear_nlink(d_inode(dentry));
@@ -710,7 +709,7 @@ static int autofs_dir_rmdir(struct inode *dir, struct dentry *dentry)
 
 	p_ino = autofs_dentry_ino(dentry->d_parent);
 	p_ino->count--;
-	dput(ino->dentry);
+	dput(dentry);
 	d_inode(dentry)->i_size = 0;
 	clear_nlink(d_inode(dentry));
 
-- 
2.47.3

[PATCH 29/39] convert autofs

[Al Viro]

creation/removal is via normal VFS paths; make ->mkdir() and ->symlink()
use d_make_persistent(); ->rmdir() and ->unlink() - d_make_discardable()
instead of dput() and that's it.

d_make_persistent() works for unhashed just fine...

Note that only persistent dentries are ever hashed there; unusual absense
of ->d_delete() in dentry_operations is due to that - anything that has
refcount reach 0 will be unhashed there, so it won't get to checking
->d_delete anyway.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/autofs/inode.c |  2 +-
 fs/autofs/root.c  | 10 ++++------
 2 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/fs/autofs/inode.c b/fs/autofs/inode.c
index f5c16ffba013..eb86f893efbb 100644
--- a/fs/autofs/inode.c
+++ b/fs/autofs/inode.c
@@ -55,7 +55,7 @@ void autofs_kill_sb(struct super_block *sb)
 	}
 
 	pr_debug("shutting down\n");
-	kill_litter_super(sb);
+	kill_anon_super(sb);
 	if (sbi)
 		kfree_rcu(sbi, rcu);
 }
diff --git a/fs/autofs/root.c b/fs/autofs/root.c
index 39794633d484..fb6c8215456c 100644
--- a/fs/autofs/root.c
+++ b/fs/autofs/root.c
@@ -594,9 +594,8 @@ static int autofs_dir_symlink(struct mnt_idmap *idmap,
 	}
 	inode->i_private = cp;
 	inode->i_size = size;
-	d_add(dentry, inode);
 
-	dget(dentry);
+	d_make_persistent(dentry, inode);
 	p_ino = autofs_dentry_ino(dentry->d_parent);
 	p_ino->count++;
 
@@ -627,7 +626,7 @@ static int autofs_dir_unlink(struct inode *dir, struct dentry *dentry)
 
 	p_ino = autofs_dentry_ino(dentry->d_parent);
 	p_ino->count--;
-	dput(dentry);
+	d_make_discardable(dentry);
 
 	d_inode(dentry)->i_size = 0;
 	clear_nlink(d_inode(dentry));
@@ -709,7 +708,7 @@ static int autofs_dir_rmdir(struct inode *dir, struct dentry *dentry)
 
 	p_ino = autofs_dentry_ino(dentry->d_parent);
 	p_ino->count--;
-	dput(dentry);
+	d_make_discardable(dentry);
 	d_inode(dentry)->i_size = 0;
 	clear_nlink(d_inode(dentry));
 
@@ -739,12 +738,11 @@ static struct dentry *autofs_dir_mkdir(struct mnt_idmap *idmap,
 	inode = autofs_get_inode(dir->i_sb, S_IFDIR | mode);
 	if (!inode)
 		return ERR_PTR(-ENOMEM);
-	d_add(dentry, inode);
 
 	if (sbi->version < 5)
 		autofs_set_leaf_automount_flags(dentry);
 
-	dget(dentry);
+	d_make_persistent(dentry, inode);
 	p_ino = autofs_dentry_ino(dentry->d_parent);
 	p_ino->count++;
 	inc_nlink(dir);
-- 
2.47.3

[PATCH 30/39] convert binfmt_misc

[Al Viro]

removals are done with locked_recursive_removal(); switch creations to
simple_start_creating()/d_make_persistent()/simple_done_creating() and
take them to a helper (add_entry()), while we are at it - simpler control
flow that way.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/binfmt_misc.c | 69 ++++++++++++++++++++++--------------------------
 1 file changed, 32 insertions(+), 37 deletions(-)

diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index a839f960cd4a..2093f9dcd321 100644
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -765,14 +765,41 @@ static const struct file_operations bm_entry_operations = {
 
 /* /register */
 
+/* add to filesystem */
+static int add_entry(Node *e, struct super_block *sb)
+{
+	struct dentry *dentry = simple_start_creating(sb->s_root, e->name);
+	struct inode *inode;
+	struct binfmt_misc *misc;
+
+	if (IS_ERR(dentry))
+		return PTR_ERR(dentry);
+
+	inode = bm_get_inode(sb, S_IFREG | 0644);
+	if (unlikely(!inode)) {
+		simple_done_creating(dentry);
+		return -ENOMEM;
+	}
+
+	refcount_set(&e->users, 1);
+	e->dentry = dentry;
+	inode->i_private = e;
+	inode->i_fop = &bm_entry_operations;
+
+	d_make_persistent(dentry, inode);
+	misc = i_binfmt_misc(inode);
+	write_lock(&misc->entries_lock);
+	list_add(&e->list, &misc->entries);
+	write_unlock(&misc->entries_lock);
+	simple_done_creating(dentry);
+	return 0;
+}
+
 static ssize_t bm_register_write(struct file *file, const char __user *buffer,
 			       size_t count, loff_t *ppos)
 {
 	Node *e;
-	struct inode *inode;
 	struct super_block *sb = file_inode(file)->i_sb;
-	struct dentry *root = sb->s_root, *dentry;
-	struct binfmt_misc *misc;
 	int err = 0;
 	struct file *f = NULL;
 
@@ -803,39 +830,7 @@ static ssize_t bm_register_write(struct file *file, const char __user *buffer,
 		e->interp_file = f;
 	}
 
-	inode_lock(d_inode(root));
-	dentry = lookup_noperm(&QSTR(e->name), root);
-	err = PTR_ERR(dentry);
-	if (IS_ERR(dentry))
-		goto out;
-
-	err = -EEXIST;
-	if (d_really_is_positive(dentry))
-		goto out2;
-
-	inode = bm_get_inode(sb, S_IFREG | 0644);
-
-	err = -ENOMEM;
-	if (!inode)
-		goto out2;
-
-	refcount_set(&e->users, 1);
-	e->dentry = dget(dentry);
-	inode->i_private = e;
-	inode->i_fop = &bm_entry_operations;
-
-	d_instantiate(dentry, inode);
-	misc = i_binfmt_misc(inode);
-	write_lock(&misc->entries_lock);
-	list_add(&e->list, &misc->entries);
-	write_unlock(&misc->entries_lock);
-
-	err = 0;
-out2:
-	dput(dentry);
-out:
-	inode_unlock(d_inode(root));
-
+	err = add_entry(e, sb);
 	if (err) {
 		if (f)
 			filp_close(f, NULL);
@@ -1028,7 +1023,7 @@ static struct file_system_type bm_fs_type = {
 	.name		= "binfmt_misc",
 	.init_fs_context = bm_init_fs_context,
 	.fs_flags	= FS_USERNS_MOUNT,
-	.kill_sb	= kill_litter_super,
+	.kill_sb	= kill_anon_super,
 };
 MODULE_ALIAS_FS("binfmt_misc");
 
-- 
2.47.3

[PATCH 31/39] convert selinuxfs

[Al Viro]

Tree has invariant part + two subtrees that get replaced upon each
policy load.  Invariant parts stay for the lifetime of filesystem,
these two subdirs - from policy load to policy load (serialized
on lock_rename(root, ...)).

All object creations are via d_alloc_name()+d_add() inside selinuxfs,
all removals are via simple_recursive_removal().

Turn those d_add() into d_make_persistent()+dput() and that's mostly it.
Don't bother to store the dentry of /policy_capabilities - it belongs
to invariant part of tree and we only use it to populate that directory,
so there's no reason to keep it around afterwards.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 security/selinux/selinuxfs.c | 52 +++++++++++++++++++++---------------
 1 file changed, 30 insertions(+), 22 deletions(-)

diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index 9aa1d03ab612..dc1bb49664f2 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -75,7 +75,6 @@ struct selinux_fs_info {
 	struct dentry *class_dir;
 	unsigned long last_class_ino;
 	bool policy_opened;
-	struct dentry *policycap_dir;
 	unsigned long last_ino;
 	struct super_block *sb;
 };
@@ -1404,7 +1403,8 @@ static int sel_make_bools(struct selinux_policy *newpolicy, struct dentry *bool_
 		isec->initialized = LABEL_INITIALIZED;
 		inode->i_fop = &sel_bool_ops;
 		inode->i_ino = i|SEL_BOOL_INO_OFFSET;
-		d_add(dentry, inode);
+		d_make_persistent(dentry, inode);
+		dput(dentry);
 	}
 out:
 	free_page((unsigned long)page);
@@ -1614,7 +1614,8 @@ static int sel_make_avc_files(struct dentry *dir)
 
 		inode->i_fop = files[i].ops;
 		inode->i_ino = ++fsi->last_ino;
-		d_add(dentry, inode);
+		d_make_persistent(dentry, inode);
+		dput(dentry);
 	}
 
 	return 0;
@@ -1645,7 +1646,8 @@ static int sel_make_ss_files(struct dentry *dir)
 
 		inode->i_fop = files[i].ops;
 		inode->i_ino = ++fsi->last_ino;
-		d_add(dentry, inode);
+		d_make_persistent(dentry, inode);
+		dput(dentry);
 	}
 
 	return 0;
@@ -1696,7 +1698,8 @@ static int sel_make_initcon_files(struct dentry *dir)
 
 		inode->i_fop = &sel_initcon_ops;
 		inode->i_ino = i|SEL_INITCON_INO_OFFSET;
-		d_add(dentry, inode);
+		d_make_persistent(dentry, inode);
+		dput(dentry);
 	}
 
 	return 0;
@@ -1800,7 +1803,8 @@ static int sel_make_perm_files(struct selinux_policy *newpolicy,
 		inode->i_fop = &sel_perm_ops;
 		/* i+1 since perm values are 1-indexed */
 		inode->i_ino = sel_perm_to_ino(classvalue, i + 1);
-		d_add(dentry, inode);
+		d_make_persistent(dentry, inode);
+		dput(dentry);
 	}
 	rc = 0;
 out:
@@ -1831,7 +1835,8 @@ static int sel_make_class_dir_entries(struct selinux_policy *newpolicy,
 
 	inode->i_fop = &sel_class_ops;
 	inode->i_ino = sel_class_to_ino(index);
-	d_add(dentry, inode);
+	d_make_persistent(dentry, inode);
+	dput(dentry);
 
 	dentry = sel_make_dir(dir, "perms", &fsi->last_class_ino);
 	if (IS_ERR(dentry))
@@ -1879,7 +1884,7 @@ static int sel_make_classes(struct selinux_policy *newpolicy,
 	return rc;
 }
 
-static int sel_make_policycap(struct selinux_fs_info *fsi)
+static int sel_make_policycap(struct selinux_fs_info *fsi, struct dentry *dir)
 {
 	unsigned int iter;
 	struct dentry *dentry = NULL;
@@ -1887,10 +1892,10 @@ static int sel_make_policycap(struct selinux_fs_info *fsi)
 
 	for (iter = 0; iter <= POLICYDB_CAP_MAX; iter++) {
 		if (iter < ARRAY_SIZE(selinux_policycap_names))
-			dentry = d_alloc_name(fsi->policycap_dir,
+			dentry = d_alloc_name(dir,
 					      selinux_policycap_names[iter]);
 		else
-			dentry = d_alloc_name(fsi->policycap_dir, "unknown");
+			dentry = d_alloc_name(dir, "unknown");
 
 		if (dentry == NULL)
 			return -ENOMEM;
@@ -1903,7 +1908,8 @@ static int sel_make_policycap(struct selinux_fs_info *fsi)
 
 		inode->i_fop = &sel_policycap_ops;
 		inode->i_ino = iter | SEL_POLICYCAP_INO_OFFSET;
-		d_add(dentry, inode);
+		d_make_persistent(dentry, inode);
+		dput(dentry);
 	}
 
 	return 0;
@@ -1929,11 +1935,12 @@ static struct dentry *sel_make_dir(struct dentry *dir, const char *name,
 	inode->i_ino = ++(*ino);
 	/* directory inodes start off with i_nlink == 2 (for "." entry) */
 	inc_nlink(inode);
-	d_add(dentry, inode);
+	d_make_persistent(dentry, inode);
 	/* bump link count on parent directory, too */
 	inc_nlink(d_inode(dir));
 
-	return dentry;
+	dput(dentry);
+	return dentry; // borrowed
 }
 
 static int reject_all(struct mnt_idmap *idmap, struct inode *inode, int mask)
@@ -1966,10 +1973,11 @@ static struct dentry *sel_make_swapover_dir(struct super_block *sb,
 	/* directory inodes start off with i_nlink == 2 (for "." entry) */
 	inc_nlink(inode);
 	inode_lock(sb->s_root->d_inode);
-	d_add(dentry, inode);
+	d_make_persistent(dentry, inode);
 	inc_nlink(sb->s_root->d_inode);
 	inode_unlock(sb->s_root->d_inode);
-	return dentry;
+	dput(dentry);
+	return dentry;	// borrowed
 }
 
 #define NULL_FILE_NAME "null"
@@ -2040,7 +2048,8 @@ static int sel_fill_super(struct super_block *sb, struct fs_context *fc)
 	isec->initialized = LABEL_INITIALIZED;
 
 	init_special_inode(inode, S_IFCHR | S_IRUGO | S_IWUGO, MKDEV(MEM_MAJOR, 3));
-	d_add(dentry, inode);
+	d_make_persistent(dentry, inode);
+	dput(dentry);
 
 	dentry = sel_make_dir(sb->s_root, "avc", &fsi->last_ino);
 	if (IS_ERR(dentry)) {
@@ -2079,15 +2088,14 @@ static int sel_fill_super(struct super_block *sb, struct fs_context *fc)
 		goto err;
 	}
 
-	fsi->policycap_dir = sel_make_dir(sb->s_root, POLICYCAP_DIR_NAME,
+	dentry = sel_make_dir(sb->s_root, POLICYCAP_DIR_NAME,
 					  &fsi->last_ino);
-	if (IS_ERR(fsi->policycap_dir)) {
-		ret = PTR_ERR(fsi->policycap_dir);
-		fsi->policycap_dir = NULL;
+	if (IS_ERR(dentry)) {
+		ret = PTR_ERR(dentry);
 		goto err;
 	}
 
-	ret = sel_make_policycap(fsi);
+	ret = sel_make_policycap(fsi, dentry);
 	if (ret) {
 		pr_err("SELinux: failed to load policy capabilities\n");
 		goto err;
@@ -2119,7 +2127,7 @@ static int sel_init_fs_context(struct fs_context *fc)
 static void sel_kill_sb(struct super_block *sb)
 {
 	selinux_fs_info_free(sb);
-	kill_litter_super(sb);
+	kill_anon_super(sb);
 }
 
 static struct file_system_type sel_fs_type = {
-- 
2.47.3

Re: [PATCH 31/39] convert selinuxfs

[Paul Moore]

On Sat, Sep 20, 2025 at 3:48 AM Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> Tree has invariant part + two subtrees that get replaced upon each
> policy load.  Invariant parts stay for the lifetime of filesystem,
> these two subdirs - from policy load to policy load (serialized
> on lock_rename(root, ...)).
>
> All object creations are via d_alloc_name()+d_add() inside selinuxfs,
> all removals are via simple_recursive_removal().
>
> Turn those d_add() into d_make_persistent()+dput() and that's mostly it.
> Don't bother to store the dentry of /policy_capabilities - it belongs
> to invariant part of tree and we only use it to populate that directory,
> so there's no reason to keep it around afterwards.

Minor comment on that below, as well as a comment style nitpick, but
overall no major concerns from me.

Acked-by: Paul Moore <paul@paul-moore.com>

> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
> ---
>  security/selinux/selinuxfs.c | 52 +++++++++++++++++++++---------------
>  1 file changed, 30 insertions(+), 22 deletions(-)

...

> diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
> index 9aa1d03ab612..dc1bb49664f2 100644
> --- a/security/selinux/selinuxfs.c
> +++ b/security/selinux/selinuxfs.c
> @@ -1966,10 +1973,11 @@ static struct dentry *sel_make_swapover_dir(struct super_block *sb,
>         /* directory inodes start off with i_nlink == 2 (for "." entry) */
>         inc_nlink(inode);
>         inode_lock(sb->s_root->d_inode);
> -       d_add(dentry, inode);
> +       d_make_persistent(dentry, inode);
>         inc_nlink(sb->s_root->d_inode);
>         inode_unlock(sb->s_root->d_inode);
> -       return dentry;
> +       dput(dentry);
> +       return dentry;  // borrowed
>  }

Prefer C style comments on their own line:

  dput(dentry);
  /* borrowed dentry */
  return dentry;

> @@ -2079,15 +2088,14 @@ static int sel_fill_super(struct super_block *sb, struct fs_context *fc)
>                 goto err;
>         }
>
> -       fsi->policycap_dir = sel_make_dir(sb->s_root, POLICYCAP_DIR_NAME,
> +       dentry = sel_make_dir(sb->s_root, POLICYCAP_DIR_NAME,
>                                           &fsi->last_ino);

I'd probably keep fsi->policycap_dir in this patch simply to limit the
scope of this patch to just the DCACHE_PERSISTENT related changes, but
I'm not going to make a big fuss about that.

> -       if (IS_ERR(fsi->policycap_dir)) {
> -               ret = PTR_ERR(fsi->policycap_dir);
> -               fsi->policycap_dir = NULL;
> +       if (IS_ERR(dentry)) {
> +               ret = PTR_ERR(dentry);
>                 goto err;
>         }
>
> -       ret = sel_make_policycap(fsi);
> +       ret = sel_make_policycap(fsi, dentry);
>         if (ret) {
>                 pr_err("SELinux: failed to load policy capabilities\n");
>                 goto err;

-- 
paul-moore.com

Re: [PATCH 31/39] convert selinuxfs

[Al Viro]

On Sun, Sep 21, 2025 at 04:44:28PM -0400, Paul Moore wrote:
> On Sat, Sep 20, 2025 at 3:48 AM Al Viro <viro@zeniv.linux.org.uk> wrote:
> >
> > Tree has invariant part + two subtrees that get replaced upon each
> > policy load.  Invariant parts stay for the lifetime of filesystem,
> > these two subdirs - from policy load to policy load (serialized
> > on lock_rename(root, ...)).
> >
> > All object creations are via d_alloc_name()+d_add() inside selinuxfs,
> > all removals are via simple_recursive_removal().
> >
> > Turn those d_add() into d_make_persistent()+dput() and that's mostly it.
> > Don't bother to store the dentry of /policy_capabilities - it belongs
> > to invariant part of tree and we only use it to populate that directory,
> > so there's no reason to keep it around afterwards.
> 
> Minor comment on that below, as well as a comment style nitpick, but
> overall no major concerns from me.

FWIW, how's this for the preparatory part?

commit 17f3b70a28233078dd3dae3cf773b68fcd899950
Author: Al Viro <viro@zeniv.linux.org.uk>
Date:   Sun Sep 21 18:09:48 2025 -0400

    selinuxfs: don't stash the dentry of /policy_capabilities
    
    Don't bother to store the dentry of /policy_capabilities - it belongs
    to invariant part of tree and we only use it to populate that directory,
    so there's no reason to keep it around afterwards.
    
    Same situation as with /avc, /ss, etc.  There are two directories that
    get replaced on policy load - /class and /booleans.  These we need to
    stash (and update the pointers on policy reload); /policy_capabilities
    is not in the same boat.
    
    Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index 9aa1d03ab612..482a2cac9640 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -75,7 +75,6 @@ struct selinux_fs_info {
 	struct dentry *class_dir;
 	unsigned long last_class_ino;
 	bool policy_opened;
-	struct dentry *policycap_dir;
 	unsigned long last_ino;
 	struct super_block *sb;
 };
@@ -117,7 +116,6 @@ static void selinux_fs_info_free(struct super_block *sb)
 
 #define BOOL_DIR_NAME "booleans"
 #define CLASS_DIR_NAME "class"
-#define POLICYCAP_DIR_NAME "policy_capabilities"
 
 #define TMPBUFLEN	12
 static ssize_t sel_read_enforce(struct file *filp, char __user *buf,
@@ -1879,23 +1877,24 @@ static int sel_make_classes(struct selinux_policy *newpolicy,
 	return rc;
 }
 
-static int sel_make_policycap(struct selinux_fs_info *fsi)
+static int sel_make_policycap(struct dentry *dir)
 {
+	struct super_block *sb = dir->d_sb;
 	unsigned int iter;
 	struct dentry *dentry = NULL;
 	struct inode *inode = NULL;
 
 	for (iter = 0; iter <= POLICYDB_CAP_MAX; iter++) {
 		if (iter < ARRAY_SIZE(selinux_policycap_names))
-			dentry = d_alloc_name(fsi->policycap_dir,
+			dentry = d_alloc_name(dir,
 					      selinux_policycap_names[iter]);
 		else
-			dentry = d_alloc_name(fsi->policycap_dir, "unknown");
+			dentry = d_alloc_name(dir, "unknown");
 
 		if (dentry == NULL)
 			return -ENOMEM;
 
-		inode = sel_make_inode(fsi->sb, S_IFREG | 0444);
+		inode = sel_make_inode(sb, S_IFREG | 0444);
 		if (inode == NULL) {
 			dput(dentry);
 			return -ENOMEM;
@@ -2079,15 +2078,13 @@ static int sel_fill_super(struct super_block *sb, struct fs_context *fc)
 		goto err;
 	}
 
-	fsi->policycap_dir = sel_make_dir(sb->s_root, POLICYCAP_DIR_NAME,
-					  &fsi->last_ino);
-	if (IS_ERR(fsi->policycap_dir)) {
-		ret = PTR_ERR(fsi->policycap_dir);
-		fsi->policycap_dir = NULL;
+	dentry = sel_make_dir(sb->s_root, "policy_capabilities", &fsi->last_ino);
+	if (IS_ERR(dentry)) {
+		ret = PTR_ERR(dentry);
 		goto err;
 	}
 
-	ret = sel_make_policycap(fsi);
+	ret = sel_make_policycap(dentry);
 	if (ret) {
 		pr_err("SELinux: failed to load policy capabilities\n");
 		goto err;

Re: [PATCH 31/39] convert selinuxfs

[Paul Moore]

On Sun, Sep 21, 2025 at 6:26 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
> On Sun, Sep 21, 2025 at 04:44:28PM -0400, Paul Moore wrote:
> > On Sat, Sep 20, 2025 at 3:48 AM Al Viro <viro@zeniv.linux.org.uk> wrote:
> > >
> > > Tree has invariant part + two subtrees that get replaced upon each
> > > policy load.  Invariant parts stay for the lifetime of filesystem,
> > > these two subdirs - from policy load to policy load (serialized
> > > on lock_rename(root, ...)).
> > >
> > > All object creations are via d_alloc_name()+d_add() inside selinuxfs,
> > > all removals are via simple_recursive_removal().
> > >
> > > Turn those d_add() into d_make_persistent()+dput() and that's mostly it.
> > > Don't bother to store the dentry of /policy_capabilities - it belongs
> > > to invariant part of tree and we only use it to populate that directory,
> > > so there's no reason to keep it around afterwards.
> >
> > Minor comment on that below, as well as a comment style nitpick, but
> > overall no major concerns from me.
>
> FWIW, how's this for the preparatory part?
>
> commit 17f3b70a28233078dd3dae3cf773b68fcd899950
> Author: Al Viro <viro@zeniv.linux.org.uk>
> Date:   Sun Sep 21 18:09:48 2025 -0400
>
>     selinuxfs: don't stash the dentry of /policy_capabilities
>
>     Don't bother to store the dentry of /policy_capabilities - it belongs
>     to invariant part of tree and we only use it to populate that directory,
>     so there's no reason to keep it around afterwards.
>
>     Same situation as with /avc, /ss, etc.  There are two directories that
>     get replaced on policy load - /class and /booleans.  These we need to
>     stash (and update the pointers on policy reload); /policy_capabilities
>     is not in the same boat.
>
>     Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Looks good to me, ACK below.  For me personally, it's a bit late to
take non-bugfix stuff for the upcoming merge window so I would defer
this for a few weeks, but if you want to take it now that's your call.
Also your call if you would prefer this to go in with the rest of the
patchset you've working on, or if you want me to take it via the
SELinux tree.  Let me know.

Acked-by: Paul Moore <paul@paul-moore.com>

> diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
> index 9aa1d03ab612..482a2cac9640 100644
> --- a/security/selinux/selinuxfs.c
> +++ b/security/selinux/selinuxfs.c
> @@ -75,7 +75,6 @@ struct selinux_fs_info {
>         struct dentry *class_dir;
>         unsigned long last_class_ino;
>         bool policy_opened;
> -       struct dentry *policycap_dir;
>         unsigned long last_ino;
>         struct super_block *sb;
>  };
> @@ -117,7 +116,6 @@ static void selinux_fs_info_free(struct super_block *sb)
>
>  #define BOOL_DIR_NAME "booleans"
>  #define CLASS_DIR_NAME "class"
> -#define POLICYCAP_DIR_NAME "policy_capabilities"
>
>  #define TMPBUFLEN      12
>  static ssize_t sel_read_enforce(struct file *filp, char __user *buf,
> @@ -1879,23 +1877,24 @@ static int sel_make_classes(struct selinux_policy *newpolicy,
>         return rc;
>  }
>
> -static int sel_make_policycap(struct selinux_fs_info *fsi)
> +static int sel_make_policycap(struct dentry *dir)
>  {
> +       struct super_block *sb = dir->d_sb;
>         unsigned int iter;
>         struct dentry *dentry = NULL;
>         struct inode *inode = NULL;
>
>         for (iter = 0; iter <= POLICYDB_CAP_MAX; iter++) {
>                 if (iter < ARRAY_SIZE(selinux_policycap_names))
> -                       dentry = d_alloc_name(fsi->policycap_dir,
> +                       dentry = d_alloc_name(dir,
>                                               selinux_policycap_names[iter]);
>                 else
> -                       dentry = d_alloc_name(fsi->policycap_dir, "unknown");
> +                       dentry = d_alloc_name(dir, "unknown");
>
>                 if (dentry == NULL)
>                         return -ENOMEM;
>
> -               inode = sel_make_inode(fsi->sb, S_IFREG | 0444);
> +               inode = sel_make_inode(sb, S_IFREG | 0444);
>                 if (inode == NULL) {
>                         dput(dentry);
>                         return -ENOMEM;
> @@ -2079,15 +2078,13 @@ static int sel_fill_super(struct super_block *sb, struct fs_context *fc)
>                 goto err;
>         }
>
> -       fsi->policycap_dir = sel_make_dir(sb->s_root, POLICYCAP_DIR_NAME,
> -                                         &fsi->last_ino);
> -       if (IS_ERR(fsi->policycap_dir)) {
> -               ret = PTR_ERR(fsi->policycap_dir);
> -               fsi->policycap_dir = NULL;
> +       dentry = sel_make_dir(sb->s_root, "policy_capabilities", &fsi->last_ino);
> +       if (IS_ERR(dentry)) {
> +               ret = PTR_ERR(dentry);
>                 goto err;
>         }
>
> -       ret = sel_make_policycap(fsi);
> +       ret = sel_make_policycap(dentry);
>         if (ret) {
>                 pr_err("SELinux: failed to load policy capabilities\n");
>                 goto err;

-- 
paul-moore.com

Re: [PATCH 31/39] convert selinuxfs

[Al Viro]

On Sun, Sep 21, 2025 at 10:50:02PM -0400, Paul Moore wrote:

> Looks good to me, ACK below.  For me personally, it's a bit late to
> take non-bugfix stuff for the upcoming merge window so I would defer
> this for a few weeks, but if you want to take it now that's your call.
> Also your call if you would prefer this to go in with the rest of the
> patchset you've working on, or if you want me to take it via the
> SELinux tree.  Let me know.

Seeing that it's already a 41-commit patchset (rpc_pipe conversion pulled
in, now +1 from this split) with several more in the pipeline (securityfs
conversion, for starters) and it's -rc7...

I think I'll post v2 in the middle of the week, but aim for the next
cycle.  Rebase to -rc1 as soon as it comes, post v3 for review and testing,
then shove it into -next.

Especially since #work.nfsctl is in -next, so hopefully by -rc1 there won't
be any need to put merges in the middle of the series, with conversion of
nfsctl included into the series, bringing with it removal of kill_litter_super()
and (hopefully) "give configfs and apparmorfs private copies of simple_unlink()
and simple_rmdir() doing dput() instead of d_make_discardable(), then make
d_make_discardable() complain about being called on non-persistent dentries".

Speaking of additional patches into that series: AFAICS there's no reason
for selinuxfs to allocate dentry before the inode.  Doing it the other way
round simplifies the things quite a bit, IMO.  Something like this (as followup
to the previous patch):

diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index 482a2cac9640..7bee2d8bdec5 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -1197,6 +1197,25 @@ static struct inode *sel_make_inode(struct super_block *sb, umode_t mode)
 	return ret;
 }
 
+static struct dentry *sel_attach(struct dentry *parent, const char *name,
+				 struct inode *inode)
+{
+	struct dentry *dentry = d_alloc_name(parent, name);
+	if (unlikely(!dentry)) {
+		iput(inode);
+		return ERR_PTR(-ENOMEM);
+	}
+	d_add(dentry, inode);
+	return dentry;
+}
+
+static int sel_attach_file(struct dentry *parent, const char *name,
+			   struct inode *inode)
+{
+	struct dentry *dentry = sel_attach(parent, name, inode);
+	return PTR_ERR_OR_ZERO(dentry);
+}
+
 static ssize_t sel_read_bool(struct file *filep, char __user *buf,
 			     size_t count, loff_t *ppos)
 {
@@ -1364,8 +1383,7 @@ static int sel_make_bools(struct selinux_policy *newpolicy, struct dentry *bool_
 	*bool_num = num;
 	*bool_pending_names = names;
 
-	for (i = 0; i < num; i++) {
-		struct dentry *dentry;
+	for (i = 0; !ret && i < num; i++) {
 		struct inode *inode;
 		struct inode_security_struct *isec;
 		ssize_t len;
@@ -1376,15 +1394,9 @@ static int sel_make_bools(struct selinux_policy *newpolicy, struct dentry *bool_
 			ret = -ENAMETOOLONG;
 			break;
 		}
-		dentry = d_alloc_name(bool_dir, names[i]);
-		if (!dentry) {
-			ret = -ENOMEM;
-			break;
-		}
 
 		inode = sel_make_inode(bool_dir->d_sb, S_IFREG | S_IRUGO | S_IWUSR);
 		if (!inode) {
-			dput(dentry);
 			ret = -ENOMEM;
 			break;
 		}
@@ -1402,7 +1414,8 @@ static int sel_make_bools(struct selinux_policy *newpolicy, struct dentry *bool_
 		isec->initialized = LABEL_INITIALIZED;
 		inode->i_fop = &sel_bool_ops;
 		inode->i_ino = i|SEL_BOOL_INO_OFFSET;
-		d_add(dentry, inode);
+
+		ret = sel_attach_file(bool_dir, names[i], inode);
 	}
 out:
 	free_page((unsigned long)page);
@@ -1587,6 +1600,7 @@ static int sel_make_avc_files(struct dentry *dir)
 	struct super_block *sb = dir->d_sb;
 	struct selinux_fs_info *fsi = sb->s_fs_info;
 	unsigned int i;
+	int err = 0;
 	static const struct tree_descr files[] = {
 		{ "cache_threshold",
 		  &sel_avc_cache_threshold_ops, S_IRUGO|S_IWUSR },
@@ -1596,26 +1610,20 @@ static int sel_make_avc_files(struct dentry *dir)
 #endif
 	};
 
-	for (i = 0; i < ARRAY_SIZE(files); i++) {
+	for (i = 0; !err && i < ARRAY_SIZE(files); i++) {
 		struct inode *inode;
-		struct dentry *dentry;
-
-		dentry = d_alloc_name(dir, files[i].name);
-		if (!dentry)
-			return -ENOMEM;
 
 		inode = sel_make_inode(dir->d_sb, S_IFREG|files[i].mode);
-		if (!inode) {
-			dput(dentry);
+		if (!inode)
 			return -ENOMEM;
-		}
 
 		inode->i_fop = files[i].ops;
 		inode->i_ino = ++fsi->last_ino;
-		d_add(dentry, inode);
+
+		err = sel_attach_file(dir, files[i].name, inode);
 	}
 
-	return 0;
+	return err;
 }
 
 static int sel_make_ss_files(struct dentry *dir)
@@ -1623,30 +1631,25 @@ static int sel_make_ss_files(struct dentry *dir)
 	struct super_block *sb = dir->d_sb;
 	struct selinux_fs_info *fsi = sb->s_fs_info;
 	unsigned int i;
+	int err = 0;
 	static const struct tree_descr files[] = {
 		{ "sidtab_hash_stats", &sel_sidtab_hash_stats_ops, S_IRUGO },
 	};
 
-	for (i = 0; i < ARRAY_SIZE(files); i++) {
+	for (i = 0; !err && i < ARRAY_SIZE(files); i++) {
 		struct inode *inode;
-		struct dentry *dentry;
-
-		dentry = d_alloc_name(dir, files[i].name);
-		if (!dentry)
-			return -ENOMEM;
 
 		inode = sel_make_inode(dir->d_sb, S_IFREG|files[i].mode);
-		if (!inode) {
-			dput(dentry);
+		if (!inode)
 			return -ENOMEM;
-		}
 
 		inode->i_fop = files[i].ops;
 		inode->i_ino = ++fsi->last_ino;
-		d_add(dentry, inode);
+
+		err = sel_attach_file(dir, files[i].name, inode);
 	}
 
-	return 0;
+	return err;
 }
 
 static ssize_t sel_read_initcon(struct file *file, char __user *buf,
@@ -1674,30 +1677,25 @@ static const struct file_operations sel_initcon_ops = {
 static int sel_make_initcon_files(struct dentry *dir)
 {
 	unsigned int i;
+	int err = 0;
 
-	for (i = 1; i <= SECINITSID_NUM; i++) {
-		struct inode *inode;
-		struct dentry *dentry;
+	for (i = 1; !err && i <= SECINITSID_NUM; i++) {
 		const char *s = security_get_initial_sid_context(i);
+		struct inode *inode;
 
 		if (!s)
 			continue;
-		dentry = d_alloc_name(dir, s);
-		if (!dentry)
-			return -ENOMEM;
 
 		inode = sel_make_inode(dir->d_sb, S_IFREG|S_IRUGO);
-		if (!inode) {
-			dput(dentry);
+		if (!inode)
 			return -ENOMEM;
-		}
 
 		inode->i_fop = &sel_initcon_ops;
 		inode->i_ino = i|SEL_INITCON_INO_OFFSET;
-		d_add(dentry, inode);
+		err = sel_attach_file(dir, s, inode);
 	}
 
-	return 0;
+	return err;
 }
 
 static inline unsigned long sel_class_to_ino(u16 class)
@@ -1779,29 +1777,21 @@ static int sel_make_perm_files(struct selinux_policy *newpolicy,
 	if (rc)
 		return rc;
 
-	for (i = 0; i < nperms; i++) {
+	for (i = 0; !rc && i < nperms; i++) {
 		struct inode *inode;
-		struct dentry *dentry;
 
-		rc = -ENOMEM;
-		dentry = d_alloc_name(dir, perms[i]);
-		if (!dentry)
-			goto out;
-
-		rc = -ENOMEM;
 		inode = sel_make_inode(dir->d_sb, S_IFREG|S_IRUGO);
 		if (!inode) {
-			dput(dentry);
-			goto out;
+			rc = -ENOMEM;
+			break;
 		}
 
 		inode->i_fop = &sel_perm_ops;
 		/* i+1 since perm values are 1-indexed */
 		inode->i_ino = sel_perm_to_ino(classvalue, i + 1);
-		d_add(dentry, inode);
+
+		rc = sel_attach_file(dir, perms[i], inode);
 	}
-	rc = 0;
-out:
 	for (i = 0; i < nperms; i++)
 		kfree(perms[i]);
 	kfree(perms);
@@ -1816,20 +1806,18 @@ static int sel_make_class_dir_entries(struct selinux_policy *newpolicy,
 	struct selinux_fs_info *fsi = sb->s_fs_info;
 	struct dentry *dentry = NULL;
 	struct inode *inode = NULL;
-
-	dentry = d_alloc_name(dir, "index");
-	if (!dentry)
-		return -ENOMEM;
+	int err;
 
 	inode = sel_make_inode(dir->d_sb, S_IFREG|S_IRUGO);
-	if (!inode) {
-		dput(dentry);
+	if (!inode)
 		return -ENOMEM;
-	}
 
 	inode->i_fop = &sel_class_ops;
 	inode->i_ino = sel_class_to_ino(index);
-	d_add(dentry, inode);
+
+	err = sel_attach_file(dir, "index", inode);
+	if (err)
+		return err;
 
 	dentry = sel_make_dir(dir, "perms", &fsi->last_class_ino);
 	if (IS_ERR(dentry))
@@ -1881,58 +1869,47 @@ static int sel_make_policycap(struct dentry *dir)
 {
 	struct super_block *sb = dir->d_sb;
 	unsigned int iter;
-	struct dentry *dentry = NULL;
 	struct inode *inode = NULL;
+	int err = 0;
+
+	for (iter = 0; !err && iter <= POLICYDB_CAP_MAX; iter++) {
+		const char *name;
 
-	for (iter = 0; iter <= POLICYDB_CAP_MAX; iter++) {
 		if (iter < ARRAY_SIZE(selinux_policycap_names))
-			dentry = d_alloc_name(dir,
-					      selinux_policycap_names[iter]);
+			name = selinux_policycap_names[iter];
 		else
-			dentry = d_alloc_name(dir, "unknown");
-
-		if (dentry == NULL)
-			return -ENOMEM;
+			name = "unknown";
 
 		inode = sel_make_inode(sb, S_IFREG | 0444);
-		if (inode == NULL) {
-			dput(dentry);
+		if (!inode)
 			return -ENOMEM;
-		}
 
 		inode->i_fop = &sel_policycap_ops;
 		inode->i_ino = iter | SEL_POLICYCAP_INO_OFFSET;
-		d_add(dentry, inode);
+		err = sel_attach_file(dir, name, inode);
 	}
 
-	return 0;
+	return err;
 }
 
 static struct dentry *sel_make_dir(struct dentry *dir, const char *name,
 			unsigned long *ino)
 {
-	struct dentry *dentry = d_alloc_name(dir, name);
 	struct inode *inode;
 
-	if (!dentry)
-		return ERR_PTR(-ENOMEM);
-
 	inode = sel_make_inode(dir->d_sb, S_IFDIR | S_IRUGO | S_IXUGO);
-	if (!inode) {
-		dput(dentry);
+	if (!inode)
 		return ERR_PTR(-ENOMEM);
-	}
 
 	inode->i_op = &simple_dir_inode_operations;
 	inode->i_fop = &simple_dir_operations;
 	inode->i_ino = ++(*ino);
 	/* directory inodes start off with i_nlink == 2 (for "." entry) */
 	inc_nlink(inode);
-	d_add(dentry, inode);
 	/* bump link count on parent directory, too */
 	inc_nlink(d_inode(dir));
 
-	return dentry;
+	return sel_attach(dir, name, inode);
 }
 
 static int reject_all(struct mnt_idmap *idmap, struct inode *inode, int mask)
@@ -2020,17 +1997,10 @@ static int sel_fill_super(struct super_block *sb, struct fs_context *fc)
 		goto err;
 	}
 
-	ret = -ENOMEM;
-	dentry = d_alloc_name(sb->s_root, NULL_FILE_NAME);
-	if (!dentry)
-		goto err;
-
 	ret = -ENOMEM;
 	inode = sel_make_inode(sb, S_IFCHR | S_IRUGO | S_IWUGO);
-	if (!inode) {
-		dput(dentry);
+	if (!inode)
 		goto err;
-	}
 
 	inode->i_ino = ++fsi->last_ino;
 	isec = selinux_inode(inode);
@@ -2039,7 +2009,9 @@ static int sel_fill_super(struct super_block *sb, struct fs_context *fc)
 	isec->initialized = LABEL_INITIALIZED;
 
 	init_special_inode(inode, S_IFCHR | S_IRUGO | S_IWUGO, MKDEV(MEM_MAJOR, 3));
-	d_add(dentry, inode);
+	ret = sel_attach_file(sb->s_root, NULL_FILE_NAME, inode);
+	if (ret)
+		goto err;
 
 	dentry = sel_make_dir(sb->s_root, "avc", &fsi->last_ino);
 	if (IS_ERR(dentry)) {

[PATCH 32/39] functionfs: switch to simple_remove_by_name()

[Al Viro]

No need to return dentry from ffs_sb_create_file() or keep it around
afterwards.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 drivers/usb/gadget/function/f_fs.c | 39 ++++++++++++------------------
 1 file changed, 15 insertions(+), 24 deletions(-)

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index 08a251df20c4..5c9a7bd4e41e 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -160,8 +160,6 @@ struct ffs_epfile {
 	struct ffs_data			*ffs;
 	struct ffs_ep			*ep;	/* P: ffs->eps_lock */
 
-	struct dentry			*dentry;
-
 	/*
 	 * Buffer for holding data from partial reads which may happen since
 	 * we’re rounding user read requests to a multiple of a max packet size.
@@ -273,9 +271,8 @@ struct ffs_desc_helper {
 static int  __must_check ffs_epfiles_create(struct ffs_data *ffs);
 static void ffs_epfiles_destroy(struct ffs_epfile *epfiles, unsigned count);
 
-static struct dentry *
-ffs_sb_create_file(struct super_block *sb, const char *name, void *data,
-		   const struct file_operations *fops);
+static int ffs_sb_create_file(struct super_block *sb, const char *name,
+			      void *data, const struct file_operations *fops);
 
 /* Devices management *******************************************************/
 
@@ -1866,9 +1863,8 @@ ffs_sb_make_inode(struct super_block *sb, void *data,
 }
 
 /* Create "regular" file */
-static struct dentry *ffs_sb_create_file(struct super_block *sb,
-					const char *name, void *data,
-					const struct file_operations *fops)
+static int ffs_sb_create_file(struct super_block *sb, const char *name,
+			      void *data, const struct file_operations *fops)
 {
 	struct ffs_data	*ffs = sb->s_fs_info;
 	struct dentry	*dentry;
@@ -1876,16 +1872,16 @@ static struct dentry *ffs_sb_create_file(struct super_block *sb,
 
 	dentry = d_alloc_name(sb->s_root, name);
 	if (!dentry)
-		return NULL;
+		return -ENOMEM;
 
 	inode = ffs_sb_make_inode(sb, data, fops, NULL, &ffs->file_perms);
 	if (!inode) {
 		dput(dentry);
-		return NULL;
+		return -ENOMEM;
 	}
 
 	d_add(dentry, inode);
-	return dentry;
+	return 0;
 }
 
 /* Super block */
@@ -1928,10 +1924,7 @@ static int ffs_sb_fill(struct super_block *sb, struct fs_context *fc)
 		return -ENOMEM;
 
 	/* EP0 file */
-	if (!ffs_sb_create_file(sb, "ep0", ffs, &ffs_ep0_operations))
-		return -ENOMEM;
-
-	return 0;
+	return ffs_sb_create_file(sb, "ep0", ffs, &ffs_ep0_operations);
 }
 
 enum {
@@ -2323,6 +2316,7 @@ static int ffs_epfiles_create(struct ffs_data *ffs)
 {
 	struct ffs_epfile *epfile, *epfiles;
 	unsigned i, count;
+	int err;
 
 	count = ffs->eps_count;
 	epfiles = kcalloc(count, sizeof(*epfiles), GFP_KERNEL);
@@ -2339,12 +2333,11 @@ static int ffs_epfiles_create(struct ffs_data *ffs)
 			sprintf(epfile->name, "ep%02x", ffs->eps_addrmap[i]);
 		else
 			sprintf(epfile->name, "ep%u", i);
-		epfile->dentry = ffs_sb_create_file(ffs->sb, epfile->name,
-						 epfile,
-						 &ffs_epfile_operations);
-		if (!epfile->dentry) {
+		err = ffs_sb_create_file(ffs->sb, epfile->name,
+					 epfile, &ffs_epfile_operations);
+		if (err) {
 			ffs_epfiles_destroy(epfiles, i - 1);
-			return -ENOMEM;
+			return err;
 		}
 	}
 
@@ -2355,13 +2348,11 @@ static int ffs_epfiles_create(struct ffs_data *ffs)
 static void ffs_epfiles_destroy(struct ffs_epfile *epfiles, unsigned count)
 {
 	struct ffs_epfile *epfile = epfiles;
+	struct dentry *root = epfile->ffs->sb->s_root;
 
 	for (; count; --count, ++epfile) {
 		BUG_ON(mutex_is_locked(&epfile->mutex));
-		if (epfile->dentry) {
-			simple_recursive_removal(epfile->dentry, NULL);
-			epfile->dentry = NULL;
-		}
+		simple_remove_by_name(root, epfile->name, NULL);
 	}
 
 	kfree(epfiles);
-- 
2.47.3

[PATCH 33/39] convert functionfs

[Al Viro]

All files are regular; ep0 is there all along, other ep* may appear
and go away during the filesystem lifetime; all of those are guaranteed
to be gone by the time we umount it.

Object creation is in ffs_sb_create_file(), removals - at ->kill_sb()
time (for ep0) or by simple_remove_by_name() from ffs_epfiles_destroy()
(for the rest of them).

Switch ffs_sb_create_file() to simple_start_creating()/d_make_persistent()/
simple_done_creating() and that's it.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 drivers/usb/gadget/function/f_fs.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index 5c9a7bd4e41e..65d9109b4051 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -1870,17 +1870,18 @@ static int ffs_sb_create_file(struct super_block *sb, const char *name,
 	struct dentry	*dentry;
 	struct inode	*inode;
 
-	dentry = d_alloc_name(sb->s_root, name);
-	if (!dentry)
-		return -ENOMEM;
-
 	inode = ffs_sb_make_inode(sb, data, fops, NULL, &ffs->file_perms);
-	if (!inode) {
-		dput(dentry);
+	if (!inode)
 		return -ENOMEM;
+	dentry = simple_start_creating(sb->s_root, name);
+	if (IS_ERR(dentry)) {
+		iput(inode);
+		return PTR_ERR(dentry);
 	}
 
-	d_add(dentry, inode);
+	d_make_persistent(dentry, inode);
+
+	simple_done_creating(dentry);
 	return 0;
 }
 
@@ -2067,7 +2068,7 @@ static int ffs_fs_init_fs_context(struct fs_context *fc)
 static void
 ffs_fs_kill_sb(struct super_block *sb)
 {
-	kill_litter_super(sb);
+	kill_anon_super(sb);
 	if (sb->s_fs_info)
 		ffs_data_closed(sb->s_fs_info);
 }
-- 
2.47.3

[PATCH 34/39] gadgetfs: switch to simple_remove_by_name()

[Al Viro]

No need to return dentry from gadgetfs_create_file() or keep it around
afterwards.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 drivers/usb/gadget/legacy/inode.c | 32 +++++++++++++------------------
 1 file changed, 13 insertions(+), 19 deletions(-)

diff --git a/drivers/usb/gadget/legacy/inode.c b/drivers/usb/gadget/legacy/inode.c
index b51e132b0cd2..fcc5f5455625 100644
--- a/drivers/usb/gadget/legacy/inode.c
+++ b/drivers/usb/gadget/legacy/inode.c
@@ -150,7 +150,6 @@ struct dev_data {
 	void				*buf;
 	wait_queue_head_t		wait;
 	struct super_block		*sb;
-	struct dentry			*dentry;
 
 	/* except this scratch i/o buffer for ep0 */
 	u8				rbuf[RBUF_SIZE];
@@ -208,7 +207,6 @@ struct ep_data {
 	struct usb_endpoint_descriptor	desc, hs_desc;
 	struct list_head		epfiles;
 	wait_queue_head_t		wait;
-	struct dentry			*dentry;
 };
 
 static inline void get_ep (struct ep_data *data)
@@ -1561,16 +1559,12 @@ static void destroy_ep_files (struct dev_data *dev)
 	spin_lock_irq (&dev->lock);
 	while (!list_empty(&dev->epfiles)) {
 		struct ep_data	*ep;
-		struct dentry	*dentry;
 
 		/* break link to FS */
 		ep = list_first_entry (&dev->epfiles, struct ep_data, epfiles);
 		list_del_init (&ep->epfiles);
 		spin_unlock_irq (&dev->lock);
 
-		dentry = ep->dentry;
-		ep->dentry = NULL;
-
 		/* break link to controller */
 		mutex_lock(&ep->lock);
 		if (ep->state == STATE_EP_ENABLED)
@@ -1581,10 +1575,11 @@ static void destroy_ep_files (struct dev_data *dev)
 		mutex_unlock(&ep->lock);
 
 		wake_up (&ep->wait);
-		put_ep (ep);
 
 		/* break link to dcache */
-		simple_recursive_removal(dentry, NULL);
+		simple_remove_by_name(dev->sb->s_root, ep->name, NULL);
+
+		put_ep (ep);
 
 		spin_lock_irq (&dev->lock);
 	}
@@ -1592,14 +1587,14 @@ static void destroy_ep_files (struct dev_data *dev)
 }
 
 
-static struct dentry *
-gadgetfs_create_file (struct super_block *sb, char const *name,
+static int gadgetfs_create_file (struct super_block *sb, char const *name,
 		void *data, const struct file_operations *fops);
 
 static int activate_ep_files (struct dev_data *dev)
 {
 	struct usb_ep	*ep;
 	struct ep_data	*data;
+	int err;
 
 	gadget_for_each_ep (ep, dev->gadget) {
 
@@ -1622,9 +1617,9 @@ static int activate_ep_files (struct dev_data *dev)
 		if (!data->req)
 			goto enomem1;
 
-		data->dentry = gadgetfs_create_file (dev->sb, data->name,
+		err = gadgetfs_create_file (dev->sb, data->name,
 				data, &ep_io_operations);
-		if (!data->dentry)
+		if (err)
 			goto enomem2;
 		list_add_tail (&data->epfiles, &dev->epfiles);
 	}
@@ -1988,8 +1983,7 @@ gadgetfs_make_inode (struct super_block *sb,
 /* creates in fs root directory, so non-renamable and non-linkable.
  * so inode and dentry are paired, until device reconfig.
  */
-static struct dentry *
-gadgetfs_create_file (struct super_block *sb, char const *name,
+static int gadgetfs_create_file (struct super_block *sb, char const *name,
 		void *data, const struct file_operations *fops)
 {
 	struct dentry	*dentry;
@@ -1997,16 +1991,16 @@ gadgetfs_create_file (struct super_block *sb, char const *name,
 
 	dentry = d_alloc_name(sb->s_root, name);
 	if (!dentry)
-		return NULL;
+		return -ENOMEM;
 
 	inode = gadgetfs_make_inode (sb, data, fops,
 			S_IFREG | (default_perm & S_IRWXUGO));
 	if (!inode) {
 		dput(dentry);
-		return NULL;
+		return -ENOMEM;
 	}
 	d_add (dentry, inode);
-	return dentry;
+	return 0;
 }
 
 static const struct super_operations gadget_fs_operations = {
@@ -2059,8 +2053,8 @@ gadgetfs_fill_super (struct super_block *sb, struct fs_context *fc)
 		goto Enomem;
 
 	dev->sb = sb;
-	dev->dentry = gadgetfs_create_file(sb, CHIP, dev, &ep0_operations);
-	if (!dev->dentry) {
+	rc = gadgetfs_create_file(sb, CHIP, dev, &ep0_operations);
+	if (rc) {
 		put_dev(dev);
 		goto Enomem;
 	}
-- 
2.47.3

[PATCH 35/39] convert gadgetfs

[Al Viro]

same as functionfs

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 drivers/usb/gadget/legacy/inode.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/drivers/usb/gadget/legacy/inode.c b/drivers/usb/gadget/legacy/inode.c
index fcc5f5455625..6b7adf153407 100644
--- a/drivers/usb/gadget/legacy/inode.c
+++ b/drivers/usb/gadget/legacy/inode.c
@@ -1989,17 +1989,20 @@ static int gadgetfs_create_file (struct super_block *sb, char const *name,
 	struct dentry	*dentry;
 	struct inode	*inode;
 
-	dentry = d_alloc_name(sb->s_root, name);
-	if (!dentry)
-		return -ENOMEM;
-
 	inode = gadgetfs_make_inode (sb, data, fops,
 			S_IFREG | (default_perm & S_IRWXUGO));
-	if (!inode) {
-		dput(dentry);
+	if (!inode)
 		return -ENOMEM;
+
+	dentry = simple_start_creating(sb->s_root, name);
+	if (IS_ERR(dentry)) {
+		iput(inode);
+		return PTR_ERR(dentry);
 	}
-	d_add (dentry, inode);
+
+	d_make_persistent(dentry, inode);
+
+	simple_done_creating(dentry);
 	return 0;
 }
 
@@ -2096,7 +2099,7 @@ static void
 gadgetfs_kill_sb (struct super_block *sb)
 {
 	mutex_lock(&sb_mutex);
-	kill_litter_super (sb);
+	kill_anon_super (sb);
 	if (the_device) {
 		put_dev (the_device);
 		the_device = NULL;
-- 
2.47.3

[PATCH 36/39] hypfs: don't pin dentries twice

[Al Viro]

hypfs dentries end up with refcount 2 when they are not busy.
Refcount 1 is enough to keep them pinned, and going that way
allows to simplify things nicely:
	* don't need to drop an extra reference before the
call of kill_litter_super() in ->kill_sb(); all we need
there is to reset the cleanup list - everything on it will
be taken out automatically.
	* we can make use of simple_recursive_removal() on
tree rebuilds; just make sure that only children of root
end up in the cleanup list and hypfs_delete_tree() becomes
much simpler

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 arch/s390/hypfs/inode.c | 41 ++++++++++-------------------------------
 1 file changed, 10 insertions(+), 31 deletions(-)

diff --git a/arch/s390/hypfs/inode.c b/arch/s390/hypfs/inode.c
index 96409573c75d..a4dc8e13d999 100644
--- a/arch/s390/hypfs/inode.c
+++ b/arch/s390/hypfs/inode.c
@@ -61,33 +61,17 @@ static void hypfs_update_update(struct super_block *sb)
 
 static void hypfs_add_dentry(struct dentry *dentry)
 {
-	dentry->d_fsdata = hypfs_last_dentry;
-	hypfs_last_dentry = dentry;
-}
-
-static void hypfs_remove(struct dentry *dentry)
-{
-	struct dentry *parent;
-
-	parent = dentry->d_parent;
-	inode_lock(d_inode(parent));
-	if (simple_positive(dentry)) {
-		if (d_is_dir(dentry))
-			simple_rmdir(d_inode(parent), dentry);
-		else
-			simple_unlink(d_inode(parent), dentry);
+	if (IS_ROOT(dentry->d_parent)) {
+		dentry->d_fsdata = hypfs_last_dentry;
+		hypfs_last_dentry = dentry;
 	}
-	d_drop(dentry);
-	dput(dentry);
-	inode_unlock(d_inode(parent));
 }
 
-static void hypfs_delete_tree(struct dentry *root)
+static void hypfs_delete_tree(void)
 {
 	while (hypfs_last_dentry) {
-		struct dentry *next_dentry;
-		next_dentry = hypfs_last_dentry->d_fsdata;
-		hypfs_remove(hypfs_last_dentry);
+		struct dentry *next_dentry = hypfs_last_dentry->d_fsdata;
+		simple_recursive_removal(hypfs_last_dentry, NULL);
 		hypfs_last_dentry = next_dentry;
 	}
 }
@@ -184,14 +168,14 @@ static ssize_t hypfs_write_iter(struct kiocb *iocb, struct iov_iter *from)
 		rc = -EBUSY;
 		goto out;
 	}
-	hypfs_delete_tree(sb->s_root);
+	hypfs_delete_tree();
 	if (machine_is_vm())
 		rc = hypfs_vm_create_files(sb->s_root);
 	else
 		rc = hypfs_diag_create_files(sb->s_root);
 	if (rc) {
 		pr_err("Updating the hypfs tree failed\n");
-		hypfs_delete_tree(sb->s_root);
+		hypfs_delete_tree();
 		goto out;
 	}
 	hypfs_update_update(sb);
@@ -326,13 +310,9 @@ static void hypfs_kill_super(struct super_block *sb)
 {
 	struct hypfs_sb_info *sb_info = sb->s_fs_info;
 
-	if (sb->s_root)
-		hypfs_delete_tree(sb->s_root);
-	if (sb_info && sb_info->update_file)
-		hypfs_remove(sb_info->update_file);
-	kfree(sb->s_fs_info);
-	sb->s_fs_info = NULL;
+	hypfs_last_dentry = NULL;
 	kill_litter_super(sb);
+	kfree(sb_info);
 }
 
 static struct dentry *hypfs_create_file(struct dentry *parent, const char *name,
@@ -367,7 +347,6 @@ static struct dentry *hypfs_create_file(struct dentry *parent, const char *name,
 		BUG();
 	inode->i_private = data;
 	d_instantiate(dentry, inode);
-	dget(dentry);
 fail:
 	inode_unlock(d_inode(parent));
 	return dentry;
-- 
2.47.3

[PATCH 37/39] hypfs: switch hypfs_create_str() to returning int

[Al Viro]

Every single caller only cares about PTR_ERR_OR_ZERO() of return value...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 arch/s390/hypfs/hypfs.h         |  3 +--
 arch/s390/hypfs/hypfs_diag_fs.c | 40 +++++++++------------------------
 arch/s390/hypfs/hypfs_vm_fs.c   |  6 ++---
 arch/s390/hypfs/inode.c         |  9 ++++----
 4 files changed, 18 insertions(+), 40 deletions(-)

diff --git a/arch/s390/hypfs/hypfs.h b/arch/s390/hypfs/hypfs.h
index 4dc2e068e0ff..0d109d956015 100644
--- a/arch/s390/hypfs/hypfs.h
+++ b/arch/s390/hypfs/hypfs.h
@@ -25,8 +25,7 @@ extern struct dentry *hypfs_mkdir(struct dentry *parent, const char *name);
 extern struct dentry *hypfs_create_u64(struct dentry *dir, const char *name,
 				       __u64 value);
 
-extern struct dentry *hypfs_create_str(struct dentry *dir, const char *name,
-				       char *string);
+extern int hypfs_create_str(struct dentry *dir, const char *name, char *string);
 
 /* LPAR Hypervisor */
 extern int hypfs_diag_init(void);
diff --git a/arch/s390/hypfs/hypfs_diag_fs.c b/arch/s390/hypfs/hypfs_diag_fs.c
index ede951dc0085..2178e6060a5d 100644
--- a/arch/s390/hypfs/hypfs_diag_fs.c
+++ b/arch/s390/hypfs/hypfs_diag_fs.c
@@ -228,8 +228,7 @@ static int hypfs_create_cpu_files(struct dentry *cpus_dir, void *cpu_info)
 			return PTR_ERR(rc);
 	}
 	diag224_idx2name(cpu_info__ctidx(diag204_get_info_type(), cpu_info), buffer);
-	rc = hypfs_create_str(cpu_dir, "type", buffer);
-	return PTR_ERR_OR_ZERO(rc);
+	return hypfs_create_str(cpu_dir, "type", buffer);
 }
 
 static void *hypfs_create_lpar_files(struct dentry *systems_dir, void *part_hdr)
@@ -276,8 +275,7 @@ static int hypfs_create_phys_cpu_files(struct dentry *cpus_dir, void *cpu_info)
 	if (IS_ERR(rc))
 		return PTR_ERR(rc);
 	diag224_idx2name(phys_cpu__ctidx(diag204_get_info_type(), cpu_info), buffer);
-	rc = hypfs_create_str(cpu_dir, "type", buffer);
-	return PTR_ERR_OR_ZERO(rc);
+	return hypfs_create_str(cpu_dir, "type", buffer);
 }
 
 static void *hypfs_create_phys_files(struct dentry *parent_dir, void *phys_hdr)
@@ -316,41 +314,25 @@ int hypfs_diag_create_files(struct dentry *root)
 		return rc;
 
 	systems_dir = hypfs_mkdir(root, "systems");
-	if (IS_ERR(systems_dir)) {
-		rc = PTR_ERR(systems_dir);
-		goto err_out;
-	}
+	if (IS_ERR(systems_dir))
+		return PTR_ERR(systems_dir);
 	time_hdr = (struct x_info_blk_hdr *)buffer;
 	part_hdr = time_hdr + info_blk_hdr__size(diag204_get_info_type());
 	for (i = 0; i < info_blk_hdr__npar(diag204_get_info_type(), time_hdr); i++) {
 		part_hdr = hypfs_create_lpar_files(systems_dir, part_hdr);
-		if (IS_ERR(part_hdr)) {
-			rc = PTR_ERR(part_hdr);
-			goto err_out;
-		}
+		if (IS_ERR(part_hdr))
+			return PTR_ERR(part_hdr);
 	}
 	if (info_blk_hdr__flags(diag204_get_info_type(), time_hdr) &
 	    DIAG204_LPAR_PHYS_FLG) {
 		ptr = hypfs_create_phys_files(root, part_hdr);
-		if (IS_ERR(ptr)) {
-			rc = PTR_ERR(ptr);
-			goto err_out;
-		}
+		if (IS_ERR(ptr))
+			return PTR_ERR(ptr);
 	}
 	hyp_dir = hypfs_mkdir(root, "hyp");
-	if (IS_ERR(hyp_dir)) {
-		rc = PTR_ERR(hyp_dir);
-		goto err_out;
-	}
-	ptr = hypfs_create_str(hyp_dir, "type", "LPAR Hypervisor");
-	if (IS_ERR(ptr)) {
-		rc = PTR_ERR(ptr);
-		goto err_out;
-	}
-	rc = 0;
-
-err_out:
-	return rc;
+	if (IS_ERR(hyp_dir))
+		return PTR_ERR(hyp_dir);
+	return hypfs_create_str(hyp_dir, "type", "LPAR Hypervisor");
 }
 
 /* Diagnose 224 functions */
diff --git a/arch/s390/hypfs/hypfs_vm_fs.c b/arch/s390/hypfs/hypfs_vm_fs.c
index 6011289afa8c..e8a32d66062b 100644
--- a/arch/s390/hypfs/hypfs_vm_fs.c
+++ b/arch/s390/hypfs/hypfs_vm_fs.c
@@ -100,11 +100,9 @@ int hypfs_vm_create_files(struct dentry *root)
 		rc = PTR_ERR(dir);
 		goto failed;
 	}
-	file = hypfs_create_str(dir, "type", "z/VM Hypervisor");
-	if (IS_ERR(file)) {
-		rc = PTR_ERR(file);
+	rc = hypfs_create_str(dir, "type", "z/VM Hypervisor");
+	if (rc)
 		goto failed;
-	}
 
 	/* physical cpus */
 	dir = hypfs_mkdir(root, "cpus");
diff --git a/arch/s390/hypfs/inode.c b/arch/s390/hypfs/inode.c
index a4dc8e13d999..c5e2d8932b88 100644
--- a/arch/s390/hypfs/inode.c
+++ b/arch/s390/hypfs/inode.c
@@ -398,24 +398,23 @@ struct dentry *hypfs_create_u64(struct dentry *dir,
 	return dentry;
 }
 
-struct dentry *hypfs_create_str(struct dentry *dir,
-				const char *name, char *string)
+int hypfs_create_str(struct dentry *dir, const char *name, char *string)
 {
 	char *buffer;
 	struct dentry *dentry;
 
 	buffer = kmalloc(strlen(string) + 2, GFP_KERNEL);
 	if (!buffer)
-		return ERR_PTR(-ENOMEM);
+		return -ENOMEM;
 	sprintf(buffer, "%s\n", string);
 	dentry =
 	    hypfs_create_file(dir, name, buffer, S_IFREG | REG_FILE_MODE);
 	if (IS_ERR(dentry)) {
 		kfree(buffer);
-		return ERR_PTR(-ENOMEM);
+		return -ENOMEM;
 	}
 	hypfs_add_dentry(dentry);
-	return dentry;
+	return 0;
 }
 
 static const struct file_operations hypfs_file_ops = {
-- 
2.47.3

[PATCH 38/39] hypfs: swich hypfs_create_u64() to returning int

[Al Viro]

same story as for hypfs_create_str()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 arch/s390/hypfs/hypfs.h         |  3 +--
 arch/s390/hypfs/hypfs_diag_fs.c | 20 ++++++++++----------
 arch/s390/hypfs/hypfs_vm_fs.c   | 15 ++++++---------
 arch/s390/hypfs/inode.c         |  9 ++++-----
 4 files changed, 21 insertions(+), 26 deletions(-)

diff --git a/arch/s390/hypfs/hypfs.h b/arch/s390/hypfs/hypfs.h
index 0d109d956015..2bb7104124ca 100644
--- a/arch/s390/hypfs/hypfs.h
+++ b/arch/s390/hypfs/hypfs.h
@@ -22,8 +22,7 @@
 
 extern struct dentry *hypfs_mkdir(struct dentry *parent, const char *name);
 
-extern struct dentry *hypfs_create_u64(struct dentry *dir, const char *name,
-				       __u64 value);
+extern int hypfs_create_u64(struct dentry *dir, const char *name, __u64 value);
 
 extern int hypfs_create_str(struct dentry *dir, const char *name, char *string);
 
diff --git a/arch/s390/hypfs/hypfs_diag_fs.c b/arch/s390/hypfs/hypfs_diag_fs.c
index 2178e6060a5d..83c9426df08e 100644
--- a/arch/s390/hypfs/hypfs_diag_fs.c
+++ b/arch/s390/hypfs/hypfs_diag_fs.c
@@ -204,7 +204,7 @@ static int hypfs_create_cpu_files(struct dentry *cpus_dir, void *cpu_info)
 {
 	struct dentry *cpu_dir;
 	char buffer[TMP_SIZE];
-	void *rc;
+	int rc;
 
 	snprintf(buffer, TMP_SIZE, "%d", cpu_info__cpu_addr(diag204_get_info_type(),
 							    cpu_info));
@@ -214,18 +214,18 @@ static int hypfs_create_cpu_files(struct dentry *cpus_dir, void *cpu_info)
 	rc = hypfs_create_u64(cpu_dir, "mgmtime",
 			      cpu_info__acc_time(diag204_get_info_type(), cpu_info) -
 			      cpu_info__lp_time(diag204_get_info_type(), cpu_info));
-	if (IS_ERR(rc))
-		return PTR_ERR(rc);
+	if (rc)
+		return rc;
 	rc = hypfs_create_u64(cpu_dir, "cputime",
 			      cpu_info__lp_time(diag204_get_info_type(), cpu_info));
-	if (IS_ERR(rc))
-		return PTR_ERR(rc);
+	if (rc)
+		return rc;
 	if (diag204_get_info_type() == DIAG204_INFO_EXT) {
 		rc = hypfs_create_u64(cpu_dir, "onlinetime",
 				      cpu_info__online_time(diag204_get_info_type(),
 							    cpu_info));
-		if (IS_ERR(rc))
-			return PTR_ERR(rc);
+		if (rc)
+			return rc;
 	}
 	diag224_idx2name(cpu_info__ctidx(diag204_get_info_type(), cpu_info), buffer);
 	return hypfs_create_str(cpu_dir, "type", buffer);
@@ -263,7 +263,7 @@ static int hypfs_create_phys_cpu_files(struct dentry *cpus_dir, void *cpu_info)
 {
 	struct dentry *cpu_dir;
 	char buffer[TMP_SIZE];
-	void *rc;
+	int rc;
 
 	snprintf(buffer, TMP_SIZE, "%i", phys_cpu__cpu_addr(diag204_get_info_type(),
 							    cpu_info));
@@ -272,8 +272,8 @@ static int hypfs_create_phys_cpu_files(struct dentry *cpus_dir, void *cpu_info)
 		return PTR_ERR(cpu_dir);
 	rc = hypfs_create_u64(cpu_dir, "mgmtime",
 			      phys_cpu__mgm_time(diag204_get_info_type(), cpu_info));
-	if (IS_ERR(rc))
-		return PTR_ERR(rc);
+	if (rc)
+		return rc;
 	diag224_idx2name(phys_cpu__ctidx(diag204_get_info_type(), cpu_info), buffer);
 	return hypfs_create_str(cpu_dir, "type", buffer);
 }
diff --git a/arch/s390/hypfs/hypfs_vm_fs.c b/arch/s390/hypfs/hypfs_vm_fs.c
index e8a32d66062b..a149a9f92e40 100644
--- a/arch/s390/hypfs/hypfs_vm_fs.c
+++ b/arch/s390/hypfs/hypfs_vm_fs.c
@@ -19,10 +19,9 @@
 
 #define ATTRIBUTE(dir, name, member) \
 do { \
-	void *rc; \
-	rc = hypfs_create_u64(dir, name, member); \
-	if (IS_ERR(rc)) \
-		return PTR_ERR(rc); \
+	int rc = hypfs_create_u64(dir, name, member); \
+	if (rc) \
+		return rc; \
 } while (0)
 
 static int hypfs_vm_create_guest(struct dentry *systems_dir,
@@ -85,7 +84,7 @@ static int hypfs_vm_create_guest(struct dentry *systems_dir,
 
 int hypfs_vm_create_files(struct dentry *root)
 {
-	struct dentry *dir, *file;
+	struct dentry *dir;
 	struct diag2fc_data *data;
 	unsigned int count = 0;
 	int rc, i;
@@ -110,11 +109,9 @@ int hypfs_vm_create_files(struct dentry *root)
 		rc = PTR_ERR(dir);
 		goto failed;
 	}
-	file = hypfs_create_u64(dir, "count", data->lcpus);
-	if (IS_ERR(file)) {
-		rc = PTR_ERR(file);
+	rc = hypfs_create_u64(dir, "count", data->lcpus);
+	if (rc)
 		goto failed;
-	}
 
 	/* guests */
 	dir = hypfs_mkdir(root, "systems");
diff --git a/arch/s390/hypfs/inode.c b/arch/s390/hypfs/inode.c
index c5e2d8932b88..6a80ab2692be 100644
--- a/arch/s390/hypfs/inode.c
+++ b/arch/s390/hypfs/inode.c
@@ -377,8 +377,7 @@ static struct dentry *hypfs_create_update_file(struct dentry *dir)
 	return dentry;
 }
 
-struct dentry *hypfs_create_u64(struct dentry *dir,
-				const char *name, __u64 value)
+int hypfs_create_u64(struct dentry *dir, const char *name, __u64 value)
 {
 	char *buffer;
 	char tmp[TMP_SIZE];
@@ -387,15 +386,15 @@ struct dentry *hypfs_create_u64(struct dentry *dir,
 	snprintf(tmp, TMP_SIZE, "%llu\n", (unsigned long long int)value);
 	buffer = kstrdup(tmp, GFP_KERNEL);
 	if (!buffer)
-		return ERR_PTR(-ENOMEM);
+		return -ENOMEM;
 	dentry =
 	    hypfs_create_file(dir, name, buffer, S_IFREG | REG_FILE_MODE);
 	if (IS_ERR(dentry)) {
 		kfree(buffer);
-		return ERR_PTR(-ENOMEM);
+		return -ENOMEM;
 	}
 	hypfs_add_dentry(dentry);
-	return dentry;
+	return 0;
 }
 
 int hypfs_create_str(struct dentry *dir, const char *name, char *string)
-- 
2.47.3

[PATCH 39/39] convert hypfs

[Al Viro]

just have hypfs_create_file() do the usual simple_start_creating()/
d_make_persistent()/simple_done_creating() and that's it

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 arch/s390/hypfs/inode.c | 23 +++++++++--------------
 1 file changed, 9 insertions(+), 14 deletions(-)

diff --git a/arch/s390/hypfs/inode.c b/arch/s390/hypfs/inode.c
index 6a80ab2692be..98952543d593 100644
--- a/arch/s390/hypfs/inode.c
+++ b/arch/s390/hypfs/inode.c
@@ -311,7 +311,7 @@ static void hypfs_kill_super(struct super_block *sb)
 	struct hypfs_sb_info *sb_info = sb->s_fs_info;
 
 	hypfs_last_dentry = NULL;
-	kill_litter_super(sb);
+	kill_anon_super(sb);
 	kfree(sb_info);
 }
 
@@ -321,17 +321,13 @@ static struct dentry *hypfs_create_file(struct dentry *parent, const char *name,
 	struct dentry *dentry;
 	struct inode *inode;
 
-	inode_lock(d_inode(parent));
-	dentry = lookup_noperm(&QSTR(name), parent);
-	if (IS_ERR(dentry)) {
-		dentry = ERR_PTR(-ENOMEM);
-		goto fail;
-	}
+	dentry = simple_start_creating(parent, name);
+	if (IS_ERR(dentry))
+		return ERR_PTR(-ENOMEM);
 	inode = hypfs_make_inode(parent->d_sb, mode);
 	if (!inode) {
-		dput(dentry);
-		dentry = ERR_PTR(-ENOMEM);
-		goto fail;
+		simple_done_creating(dentry);
+		return ERR_PTR(-ENOMEM);
 	}
 	if (S_ISREG(mode)) {
 		inode->i_fop = &hypfs_file_ops;
@@ -346,10 +342,9 @@ static struct dentry *hypfs_create_file(struct dentry *parent, const char *name,
 	} else
 		BUG();
 	inode->i_private = data;
-	d_instantiate(dentry, inode);
-fail:
-	inode_unlock(d_inode(parent));
-	return dentry;
+	d_make_persistent(dentry, inode);
+	simple_done_creating(dentry);
+	return dentry;	 // borrowed
 }
 
 struct dentry *hypfs_mkdir(struct dentry *parent, const char *name)
-- 
2.47.3

Re: [PATCHES][RFC] the meat of tree-in-dcache series

[Linus Torvalds]

On Sat, 20 Sept 2025 at 00:42, Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> The branch is -rc5-based; it lives in
> git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git #work.persistency

I reacted to the "d_make_persistent() + dput()" pattern, and wondered
if it should just use the refcount that the caller has, but it does
look like that alternate approach would just result in a
"d_make_persistent(dget()))" pattern instead.

And I guess you already get the lock for d_make_persistent(), so it's
better to do the dget while having it - but arguably that is also true
for the dput().

I think you did pick the right model, with d_make_persistent() taking
a ref, and d_make_discardable() releasing it, but this series did make
me think that the refcounting on the caller side is a bit odd.

Because some places would clearly want a "d_make_persistent_and_put()"
function. But probably not worth the extra interface.

Anyway, apart from that I only had one reaction: I think
d_make_discardable() should have a

        WARN_ON(!(dentry->d_flags & DCACHE_PERSISTENT))

because without that I think it can mistakenly be used as some kind of
"dput that always takes the dentry lock", which seems bad.

Or was that intentional for some reason?

Talking about WARN_ON() - please don't add new BUG_ON() cases. I
realize that those will never trigger, but *if* they were to trigger,
some of them would do so during early boot and be a pain for people to
ever even report to us.

BUG_ON() really should be shunned. I think it makes sense to you and
for automated testing, but it really is absolutely *horrendously* bad
for the case where the code hits actual users.

                 Linus

Re: [PATCHES][RFC] the meat of tree-in-dcache series

[Al Viro]

On Sat, Sep 20, 2025 at 09:26:27AM -0700, Linus Torvalds wrote:

> Anyway, apart from that I only had one reaction: I think
> d_make_discardable() should have a
> 
>         WARN_ON(!(dentry->d_flags & DCACHE_PERSISTENT))
> 
> because without that I think it can mistakenly be used as some kind of
> "dput that always takes the dentry lock", which seems bad.
> 
> Or was that intentional for some reason?

In the end - sure, we want that.  But in the meanwhile that would require
separate variants of simple_unlink()/simple_recursive_removal()/etc.
for those filesystems that are already marking persistent ones, with
the only difference being that warning.

A lot more noise that way.

So I'd prefer to put a warning in the source for the time being.  In principle,
by the end of series as posted we are down to very few filesystems that use
simple_unlink() and friends without having marked them persistent in the
first place, so it would be possible to put a "make d_make_discardable() warn
if it's not marked persistent, add variants of simple_unlink()/simple_rmdir()/
simple_recursive_removal()/locked_recursive_removal() that would *NOT* warn
and switch the handful of unconverted users to calling those", but...

By the end of series as posted that's down to nfsctl, rpc_pipe, securityfs,
configfs and apparmorfs.  The first 3 - because they used to have subseries
of their own in separate branches, with corresponding conversion commits
sitting on top of merges (#work.nfsctl is the last of those branches).
No real obstacle to moving them into the queue, I just wanted to post it
for review before we get to -rc7.

The remaining two (configfs and apparmor) are special enough to warrant private
copies of simple_{unlink,rmdir}().  So I'd rather have that in patch adding
the warning - simple_recursive_remove() wouldn't need a separate copy that
way at all.

configfs has a separate series untangling it, but that's a separate story -
that work goes back to 2018; I want to resurrect it, but I'm not mixing it
into this pile.

appramor is... special.  They've got locking of their own, completely broken and
interspersed with regular directory locks.  John Johansen, if I understood him
correctly, has some plans re fixing that, and I'm happy not to have analysis
of their locking on my plate.  _Maybe_ it will end up close enough to the usual
tree-in-dcache to switch to that stuff, but at the moment I'd rather open-code
simple_{unlink,rmdir} in aafs_remove() and leave it at that.