[PATCH v3 00/15] Further centralising of directory locking for name ops.

[PATCH v3 00/15] Further centralising of directory locking for name ops.

[NeilBrown]

Following Chris Mason's tool-based review, here is v3 with some fixes.
Particularly 06/15 mistakenly tested the result of start_creating for NULL
and 09/15 had some really messed up flow in error handling.
Also human-language typos fixed.

This code is in 
  github.com:neilbrown/linux.git
  branch pdirops

For anyone interested, my next batch is in branch pdirops-next

Original patch description below.

Thanks,
NeilBrown

I am working towards changing the locking rules for name-operations: locking
the name rather than the whole directory.

The current part of this process is centralising all the locking so that
it can be changed in one place.

Recently "start_creating", "start_removing", "start_renaming" and related
interaces were added which combine the locking and the lookup.  At that time
many callers were changed to use the new interfaces.  However there are still
an assortment of places out side of fs/namei.c where the directory is locked
explictly, whether with inode_lock() or lock_rename() or similar.  These were
missed in the first pass for an assortment of uninteresting reasons.

This series addresses the remaining places where explicit locking is
used, and changes them to use the new interfaces, or otherwise removes
the explicit locking.

The biggest changes are in overlayfs.  The other changes are quite
simple, though maybe the cachefiles changes is the least simple of those.

I'm running the --overlay tests in xfstests and nothing has popped yet.
I'll continue with this and run some NFS tests too.

Thanks for your review of these patches!

NeilBrown

 [PATCH v3 01/15] VFS: note error returns in documentation for various
 [PATCH v3 02/15] fs/proc: Don't lock root inode when creating "self"
 [PATCH v3 03/15] VFS: move the start_dirop() kerndoc comment to
 [PATCH v3 04/15] libfs: change simple_done_creating() to use
 [PATCH v3 05/15] Apparmor: Use simple_start_creating() /
 [PATCH v3 06/15] selinux: Use simple_start_creating() /
 [PATCH v3 07/15] nfsd: switch purge_old() to use
 [PATCH v3 08/15] VFS: make lookup_one_qstr_excl() static.
 [PATCH v3 09/15] ovl: Simplify ovl_lookup_real_one()
 [PATCH v3 10/15] cachefiles: change cachefiles_bury_object to use
 [PATCH v3 11/15] ovl: pass name buffer to ovl_start_creating_temp()
 [PATCH v3 12/15] ovl: change ovl_create_real() to get a new lock when
 [PATCH v3 13/15] ovl: use is_subdir() for testing if one thing is a
 [PATCH v3 14/15] ovl: remove ovl_lock_rename_workdir()
 [PATCH v3 15/15] VFS: unexport lock_rename(), lock_rename_child(),

[PATCH v3 01/15] VFS: note error returns in documentation for various lookup functions

[NeilBrown]

From: NeilBrown <neil@brown.name>

Darrick recently noted that try_lookup_noperm() is documented as
"Look up a dentry by name in the dcache, returning NULL if it does not
currently exist." but it can in fact return an error.

So update the documentation for that and related functions.

Link: https://lore.kernel.org/all/20260218234917.GA6490@frogsfrogsfrogs/
Cc: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
---
 fs/namei.c | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/fs/namei.c b/fs/namei.c
index 58f715f7657e..6f595f58acfe 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3124,7 +3124,8 @@ static int lookup_one_common(struct mnt_idmap *idmap,
  * @base:	base directory to lookup from
  *
  * Look up a dentry by name in the dcache, returning NULL if it does not
- * currently exist.  The function does not try to create a dentry and if one
+ * currently exist or an error if there is a problem with the name.
+ * The function does not try to create a dentry and if one
  * is found it doesn't try to revalidate it.
  *
  * Note that this routine is purely a helper for filesystem usage and should
@@ -3132,6 +3133,11 @@ static int lookup_one_common(struct mnt_idmap *idmap,
  *
  * No locks need be held - only a counted reference to @base is needed.
  *
+ * Returns:
+ *   - ref-counted dentry on success, or
+ *   - %NULL if name could not be found, or
+ *   - ERR_PTR(-EACCES) if name is dot or dotdot or contains a slash or nul, or
+ *   - ERR_PTR() if fs provide ->d_hash, and this returned an error.
  */
 struct dentry *try_lookup_noperm(struct qstr *name, struct dentry *base)
 {
@@ -3208,6 +3214,11 @@ EXPORT_SYMBOL(lookup_one);
  *
  * Unlike lookup_one, it should be called without the parent
  * i_rwsem held, and will take the i_rwsem itself if necessary.
+ *
+ * Returns: - A dentry, possibly negative, or
+ *	    - same errors as try_lookup_noperm() or
+ *	    - ERR_PTR(-ENOENT) if parent has been removed, or
+ *	    - ERR_PTR(-EACCES) if parent directory is not searchable.
  */
 struct dentry *lookup_one_unlocked(struct mnt_idmap *idmap, struct qstr *name,
 				   struct dentry *base)
@@ -3244,6 +3255,10 @@ EXPORT_SYMBOL(lookup_one_unlocked);
  * It should be called without the parent i_rwsem held, and will take
  * the i_rwsem itself if necessary.  If a fatal signal is pending or
  * delivered, it will return %-EINTR if the lock is needed.
+ *
+ * Returns: A dentry, possibly negative, or
+ *	   - same errors as lookup_one_unlocked() or
+ *	   - ERR_PTR(-EINTR) if a fatal signal is pending.
  */
 struct dentry *lookup_one_positive_killable(struct mnt_idmap *idmap,
 					    struct qstr *name,
@@ -3283,6 +3298,10 @@ EXPORT_SYMBOL(lookup_one_positive_killable);
  * This can be used for in-kernel filesystem clients such as file servers.
  *
  * The helper should be called without i_rwsem held.
+ *
+ * Returns: A positive dentry, or
+ *	   - ERR_PTR(-ENOENT) if the name could not be found, or
+ *	   - same errors as lookup_one_unlocked().
  */
 struct dentry *lookup_one_positive_unlocked(struct mnt_idmap *idmap,
 					    struct qstr *name,
@@ -3311,6 +3330,10 @@ EXPORT_SYMBOL(lookup_one_positive_unlocked);
  *
  * Unlike try_lookup_noperm() it *does* revalidate the dentry if it already
  * existed.
+ *
+ * Returns: A dentry, possibly negative, or
+ *	   - ERR_PTR(-ENOENT) if parent has been removed, or
+ *	   - same errors as try_lookup_noperm()
  */
 struct dentry *lookup_noperm_unlocked(struct qstr *name, struct dentry *base)
 {
@@ -3335,6 +3358,10 @@ EXPORT_SYMBOL(lookup_noperm_unlocked);
  * _can_ become positive at any time, so callers of lookup_noperm_unlocked()
  * need to be very careful; pinned positives have ->d_inode stable, so
  * this one avoids such problems.
+ *
+ * Returns: A positive dentry, or
+ *	   - ERR_PTR(-ENOENT) if name cannot be found or parent has been removed, or
+ *	   - same errors as try_lookup_noperm()
  */
 struct dentry *lookup_noperm_positive_unlocked(struct qstr *name,
 					       struct dentry *base)
-- 
2.50.0.107.gf914562f5916.dirty

[PATCH v3 02/15] fs/proc: Don't lock root inode when creating "self" and "thread-self"

[NeilBrown]

From: NeilBrown <neil@brown.name>

proc_setup_self() and proc_setup_thread_self() are only called from
proc_fill_super() which is before the filesystem is "live".  So there is
no need to lock the root directory when adding "self" and "thread-self".
This is clear from simple_fill_super() which provides similar
functionality for other filesystems and does not lock anything.

The locking is not harmful, except that it may be confusing to a reader.
As part of an effort to centralise all locking for directories for
name-based operations (prior to changing some locking rules), it is
simplest to remove the locking here.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
---
 fs/proc/self.c        | 3 ---
 fs/proc/thread_self.c | 3 ---
 2 files changed, 6 deletions(-)

diff --git a/fs/proc/self.c b/fs/proc/self.c
index 62d2c0cfe35c..56adf1c68f7a 100644
--- a/fs/proc/self.c
+++ b/fs/proc/self.c
@@ -35,11 +35,9 @@ unsigned self_inum __ro_after_init;
 
 int proc_setup_self(struct super_block *s)
 {
-	struct inode *root_inode = d_inode(s->s_root);
 	struct dentry *self;
 	int ret = -ENOMEM;
 
-	inode_lock(root_inode);
 	self = d_alloc_name(s->s_root, "self");
 	if (self) {
 		struct inode *inode = new_inode(s);
@@ -55,7 +53,6 @@ int proc_setup_self(struct super_block *s)
 		}
 		dput(self);
 	}
-	inode_unlock(root_inode);
 
 	if (ret)
 		pr_err("proc_fill_super: can't allocate /proc/self\n");
diff --git a/fs/proc/thread_self.c b/fs/proc/thread_self.c
index d6113dbe58e0..61ac62c3fd9f 100644
--- a/fs/proc/thread_self.c
+++ b/fs/proc/thread_self.c
@@ -35,11 +35,9 @@ 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 dentry *thread_self;
 	int ret = -ENOMEM;
 
-	inode_lock(root_inode);
 	thread_self = d_alloc_name(s->s_root, "thread-self");
 	if (thread_self) {
 		struct inode *inode = new_inode(s);
@@ -55,7 +53,6 @@ int proc_setup_thread_self(struct super_block *s)
 		}
 		dput(thread_self);
 	}
-	inode_unlock(root_inode);
 
 	if (ret)
 		pr_err("proc_fill_super: can't allocate /proc/thread-self\n");
-- 
2.50.0.107.gf914562f5916.dirty

[PATCH v3 03/15] VFS: move the start_dirop() kerndoc comment to before start_dirop()

[NeilBrown]

From: NeilBrown <neil@brown.name>

This kerneldoc comment was always meant for start_dirop(), not for
__start_dirop() which is a static function and doesn't need
documentation.

It was in the wrong place and was then incorrectly renamed (instead of
moved) and useless "documentation" was added for "@state" was provided.

This patch reverts the name, removes the mention of @state, and moves
the comment to where it belongs.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
---
 fs/namei.c | 27 +++++++++++++--------------
 1 file changed, 13 insertions(+), 14 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 6f595f58acfe..11c9a4a6c396 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2893,20 +2893,6 @@ static int filename_parentat(int dfd, struct filename *name,
 	return __filename_parentat(dfd, name, flags, parent, last, type, NULL);
 }
 
-/**
- * __start_dirop - begin a create or remove dirop, performing locking and lookup
- * @parent:       the dentry of the parent in which the operation will occur
- * @name:         a qstr holding the name within that parent
- * @lookup_flags: intent and other lookup flags.
- * @state:        task state bitmask
- *
- * The lookup is performed and necessary locks are taken so that, on success,
- * the returned dentry can be operated on safely.
- * The qstr must already have the hash value calculated.
- *
- * Returns: a locked dentry, or an error.
- *
- */
 static struct dentry *__start_dirop(struct dentry *parent, struct qstr *name,
 				    unsigned int lookup_flags,
 				    unsigned int state)
@@ -2928,6 +2914,19 @@ static struct dentry *__start_dirop(struct dentry *parent, struct qstr *name,
 	return dentry;
 }
 
+/**
+ * start_dirop - begin a create or remove dirop, performing locking and lookup
+ * @parent:       the dentry of the parent in which the operation will occur
+ * @name:         a qstr holding the name within that parent
+ * @lookup_flags: intent and other lookup flags.
+ *
+ * The lookup is performed and necessary locks are taken so that, on success,
+ * the returned dentry can be operated on safely.
+ * The qstr must already have the hash value calculated.
+ *
+ * Returns: a locked dentry, or an error.
+ *
+ */
 struct dentry *start_dirop(struct dentry *parent, struct qstr *name,
 			   unsigned int lookup_flags)
 {
-- 
2.50.0.107.gf914562f5916.dirty

[PATCH v3 04/15] libfs: change simple_done_creating() to use end_creating()

[NeilBrown]

From: NeilBrown <neil@brown.name>

simple_done_creating() and end_creating() are identical.
So change the former to use the latter.  This further centralises
unlocking of directories.

Signed-off-by: NeilBrown <neil@brown.name>
---
 fs/libfs.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/libfs.c b/fs/libfs.c
index 74134ba2e8d1..63b4fb082435 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -2318,7 +2318,6 @@ 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);
+	end_creating(child);
 }
 EXPORT_SYMBOL(simple_done_creating);
-- 
2.50.0.107.gf914562f5916.dirty

[PATCH v3 05/15] Apparmor: Use simple_start_creating() / simple_done_creating()

[NeilBrown]

From: NeilBrown <neil@brown.name>

Instead of explicitly locking the parent and performing a look up in
apparmor, use simple_start_creating(), and then simple_done_creating()
to unlock and drop the dentry.

This removes the need to check for an existing entry (as
simple_start_creating() acts like an exclusive create and can return
-EEXIST), simplifies error paths, and keeps dir locking code
centralised.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
---
 security/apparmor/apparmorfs.c | 35 ++++++++--------------------------
 1 file changed, 8 insertions(+), 27 deletions(-)

diff --git a/security/apparmor/apparmorfs.c b/security/apparmor/apparmorfs.c
index 2f84bd23edb6..f93c4f31d02a 100644
--- a/security/apparmor/apparmorfs.c
+++ b/security/apparmor/apparmorfs.c
@@ -282,32 +282,20 @@ static struct dentry *aafs_create(const char *name, umode_t mode,
 
 	dir = d_inode(parent);
 
-	inode_lock(dir);
-	dentry = lookup_noperm(&QSTR(name), parent);
+	dentry = simple_start_creating(parent, name);
 	if (IS_ERR(dentry)) {
 		error = PTR_ERR(dentry);
-		goto fail_lock;
-	}
-
-	if (d_really_is_positive(dentry)) {
-		error = -EEXIST;
-		goto fail_dentry;
+		goto fail;
 	}
 
 	error = __aafs_setup_d_inode(dir, dentry, mode, data, link, fops, iops);
+	simple_done_creating(dentry);
 	if (error)
-		goto fail_dentry;
-	inode_unlock(dir);
-
+		goto fail;
 	return dentry;
 
-fail_dentry:
-	dput(dentry);
-
-fail_lock:
-	inode_unlock(dir);
+fail:
 	simple_release_fs(&aafs_mnt, &aafs_count);
-
 	return ERR_PTR(error);
 }
 
@@ -2585,8 +2573,7 @@ static int aa_mk_null_file(struct dentry *parent)
 	if (error)
 		return error;
 
-	inode_lock(d_inode(parent));
-	dentry = lookup_noperm(&QSTR(NULL_FILE_NAME), parent);
+	dentry = simple_start_creating(parent, NULL_FILE_NAME);
 	if (IS_ERR(dentry)) {
 		error = PTR_ERR(dentry);
 		goto out;
@@ -2594,7 +2581,7 @@ static int aa_mk_null_file(struct dentry *parent)
 	inode = new_inode(parent->d_inode->i_sb);
 	if (!inode) {
 		error = -ENOMEM;
-		goto out1;
+		goto out;
 	}
 
 	inode->i_ino = get_next_ino();
@@ -2606,18 +2593,12 @@ static int aa_mk_null_file(struct dentry *parent)
 	aa_null.dentry = dget(dentry);
 	aa_null.mnt = mntget(mount);
 
-	error = 0;
-
-out1:
-	dput(dentry);
 out:
-	inode_unlock(d_inode(parent));
+	simple_done_creating(dentry);
 	simple_release_fs(&mount, &count);
 	return error;
 }
 
-
-
 static const char *policy_get_link(struct dentry *dentry,
 				   struct inode *inode,
 				   struct delayed_call *done)
-- 
2.50.0.107.gf914562f5916.dirty

[PATCH v3 06/15] selinux: Use simple_start_creating() / simple_done_creating()

[NeilBrown]

From: NeilBrown <neil@brown.name>

Instead of explicitly locking the parent and performing a lookup in
selinux, use simple_start_creating(), and then use
simple_done_creating() to unlock.

This extends the region that the directory is locked for, and also
performs a lookup.
The lock extension is of no real consequence.
The lookup uses simple_lookup() and so always succeeds.  Thus when
d_make_persistent() is called the dentry will already be hashed.
d_make_persistent() handles this case.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: NeilBrown <neil@brown.name>
---
 security/selinux/selinuxfs.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index 3245cc531555..83aa765a09f9 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -1931,27 +1931,26 @@ static const struct inode_operations swapover_dir_inode_operations = {
 static struct dentry *sel_make_swapover_dir(struct super_block *sb,
 						unsigned long *ino)
 {
-	struct dentry *dentry = d_alloc_name(sb->s_root, ".swapover");
+	struct dentry *dentry;
 	struct inode *inode;
 
-	if (!dentry)
-		return ERR_PTR(-ENOMEM);
-
 	inode = sel_make_inode(sb, S_IFDIR);
-	if (!inode) {
-		dput(dentry);
+	if (!inode)
 		return ERR_PTR(-ENOMEM);
+
+	dentry = simple_start_creating(sb->s_root, ".swapover");
+	if (IS_ERR(dentry)) {
+		iput(inode);
+		return dentry;
 	}
 
 	inode->i_op = &swapover_dir_inode_operations;
 	inode->i_ino = ++(*ino);
 	/* directory inodes start off with i_nlink == 2 (for "." entry) */
 	inc_nlink(inode);
-	inode_lock(sb->s_root->d_inode);
 	d_make_persistent(dentry, inode);
 	inc_nlink(sb->s_root->d_inode);
-	inode_unlock(sb->s_root->d_inode);
-	dput(dentry);
+	simple_done_creating(dentry);
 	return dentry;	// borrowed
 }
 
-- 
2.50.0.107.gf914562f5916.dirty

[PATCH v3 07/15] nfsd: switch purge_old() to use start_removing_noperm()

[NeilBrown]

From: NeilBrown <neil@brown.name>

Rather than explicit locking, use the start_removing_noperm() and
end_removing() wrappers.
This was not done with other start_removing changes due to conflicting
in-flight patches.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
---
 fs/nfsd/nfs4recover.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c
index b4bf85f96f6e..b338473d6e52 100644
--- a/fs/nfsd/nfs4recover.c
+++ b/fs/nfsd/nfs4recover.c
@@ -352,16 +352,14 @@ purge_old(struct dentry *parent, char *cname, struct nfsd_net *nn)
 	if (nfs4_has_reclaimed_state(name, nn))
 		goto out_free;
 
-	inode_lock_nested(d_inode(parent), I_MUTEX_PARENT);
-	child = lookup_one(&nop_mnt_idmap, &QSTR(cname), parent);
+	child = start_removing_noperm(parent, &QSTR(cname));
 	if (!IS_ERR(child)) {
 		status = vfs_rmdir(&nop_mnt_idmap, d_inode(parent), child, NULL);
 		if (status)
 			printk("failed to remove client recovery directory %pd\n",
 			       child);
-		dput(child);
 	}
-	inode_unlock(d_inode(parent));
+	end_removing(child);
 
 out_free:
 	kfree(name.data);
-- 
2.50.0.107.gf914562f5916.dirty

[PATCH v3 08/15] VFS: make lookup_one_qstr_excl() static.

[NeilBrown]

From: NeilBrown <neil@brown.name>

lookup_one_qstr_excl() is no longer used outside of namei.c, so
make it static.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
---
 Documentation/filesystems/porting.rst | 7 +++++++
 fs/namei.c                            | 5 ++---
 include/linux/namei.h                 | 3 ---
 3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/Documentation/filesystems/porting.rst b/Documentation/filesystems/porting.rst
index 52ff1d19405b..1dd31ab417a2 100644
--- a/Documentation/filesystems/porting.rst
+++ b/Documentation/filesystems/porting.rst
@@ -1361,3 +1361,10 @@ to match what strlen() would return if it was ran on the string.
 
 However, if the string is freely accessible for the duration of inode's
 lifetime, consider using inode_set_cached_link() instead.
+
+---
+
+**mandatory**
+
+lookup_one_qstr_excl() is no longer exported - use start_creating() or
+similar.
diff --git a/fs/namei.c b/fs/namei.c
index 11c9a4a6c396..a5daa62399d7 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1782,8 +1782,8 @@ static struct dentry *lookup_dcache(const struct qstr *name,
  * Will return -ENOENT if name isn't found and LOOKUP_CREATE wasn't passed.
  * Will return -EEXIST if name is found and LOOKUP_EXCL was passed.
  */
-struct dentry *lookup_one_qstr_excl(const struct qstr *name,
-				    struct dentry *base, unsigned int flags)
+static struct dentry *lookup_one_qstr_excl(const struct qstr *name,
+					   struct dentry *base, unsigned int flags)
 {
 	struct dentry *dentry;
 	struct dentry *old;
@@ -1820,7 +1820,6 @@ struct dentry *lookup_one_qstr_excl(const struct qstr *name,
 	}
 	return dentry;
 }
-EXPORT_SYMBOL(lookup_one_qstr_excl);
 
 /**
  * lookup_fast - do fast lockless (but racy) lookup of a dentry
diff --git a/include/linux/namei.h b/include/linux/namei.h
index 58600cf234bc..c7a7288cdd25 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -54,9 +54,6 @@ extern int path_pts(struct path *path);
 
 extern int user_path_at(int, const char __user *, unsigned, struct path *);
 
-struct dentry *lookup_one_qstr_excl(const struct qstr *name,
-				    struct dentry *base,
-				    unsigned int flags);
 extern int kern_path(const char *, unsigned, struct path *);
 struct dentry *kern_path_parent(const char *name, struct path *parent);
 
-- 
2.50.0.107.gf914562f5916.dirty

[PATCH v3 09/15] ovl: Simplify ovl_lookup_real_one()

[NeilBrown]

From: NeilBrown <neil@brown.name>

The primary purpose of this patch is to remove the locking from
ovl_lookup_real_one() as part of centralising all locking of directories
for name operations.

The locking here isn't needed.  By performing consistency tests after
the lookup we can be sure that the result of the lookup was valid at
least for a moment, which is all the original code promised.

lookup_noperm_unlocked() is used for the lookup and it will take the
lock if needed only where it is needed.

Also:
 - don't take a reference to real->d_parent.  The parent is
   only use for a pointer comparison, and no reference is needed for
   that.
 - Several "if" statements have a "goto" followed by "else" - the
   else isn't needed: the following statement can directly follow
   the "if" as a new statement
 - Use a consistent pattern of setting "err" before performing a test
   and possibly going to "fail".
 - remove the "out" label (now that we don't need to dput(parent) or
   unlock) and simply return from fail:.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: NeilBrown <neil@brown.name>
---
 fs/overlayfs/export.c | 71 ++++++++++++++++++++-----------------------
 1 file changed, 33 insertions(+), 38 deletions(-)

diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c
index 83f80fdb1567..896f2e9af2e2 100644
--- a/fs/overlayfs/export.c
+++ b/fs/overlayfs/export.c
@@ -349,69 +349,64 @@ static struct dentry *ovl_dentry_real_at(struct dentry *dentry, int idx)
 	return NULL;
 }
 
-/*
- * Lookup a child overlay dentry to get a connected overlay dentry whose real
- * dentry is @real. If @real is on upper layer, we lookup a child overlay
- * dentry with the same name as the real dentry. Otherwise, we need to consult
- * index for lookup.
+/**
+ * ovl_lookup_real_one -  Lookup a child overlay dentry to get an overlay dentry whose real dentry is given
+ * @connected: parent overlay dentry
+ * @real: given child real dentry
+ * @layer: layer in which @real exists
+ *
+ *
+ * Lookup a child overlay dentry in @connected with the same name as the @real
+ * dentry.  Then check that the parent of the result is the real dentry for
+ * @connected, and @real is the real dentry for the result.
+ *
+ * Returns:
+ *   %-ECHILD if the parent of @real is no longer the real dentry for @connected.
+ *   %-ESTALE if @real is not the real dentry of the found dentry.
+ *   Otherwise the found dentry is returned.
  */
 static struct dentry *ovl_lookup_real_one(struct dentry *connected,
 					  struct dentry *real,
 					  const struct ovl_layer *layer)
 {
-	struct inode *dir = d_inode(connected);
-	struct dentry *this, *parent = NULL;
+	struct dentry *this;
 	struct name_snapshot name;
 	int err;
 
 	/*
-	 * Lookup child overlay dentry by real name. The dir mutex protects us
-	 * from racing with overlay rename. If the overlay dentry that is above
-	 * real has already been moved to a parent that is not under the
-	 * connected overlay dir, we return -ECHILD and restart the lookup of
-	 * connected real path from the top.
-	 */
-	inode_lock_nested(dir, I_MUTEX_PARENT);
-	err = -ECHILD;
-	parent = dget_parent(real);
-	if (ovl_dentry_real_at(connected, layer->idx) != parent)
-		goto fail;
-
-	/*
-	 * We also need to take a snapshot of real dentry name to protect us
+	 * We need to take a snapshot of real dentry name to protect us
 	 * from racing with underlying layer rename. In this case, we don't
 	 * care about returning ESTALE, only from dereferencing a free name
 	 * pointer because we hold no lock on the real dentry.
 	 */
 	take_dentry_name_snapshot(&name, real);
-	/*
-	 * No idmap handling here: it's an internal lookup.
-	 */
-	this = lookup_noperm(&name.name, connected);
+	this = lookup_noperm_unlocked(&name.name, connected);
 	release_dentry_name_snapshot(&name);
+
+	err = -ECHILD;
+	if (ovl_dentry_real_at(connected, layer->idx) != real->d_parent)
+		goto fail;
+
 	err = PTR_ERR(this);
-	if (IS_ERR(this)) {
+	if (IS_ERR(this))
 		goto fail;
-	} else if (!this || !this->d_inode) {
-		dput(this);
-		err = -ENOENT;
+
+	err = -ENOENT;
+	if (!this || !this->d_inode)
 		goto fail;
-	} else if (ovl_dentry_real_at(this, layer->idx) != real) {
-		dput(this);
-		err = -ESTALE;
+
+	err = -ESTALE;
+	if (ovl_dentry_real_at(this, layer->idx) != real)
 		goto fail;
-	}
 
-out:
-	dput(parent);
-	inode_unlock(dir);
 	return this;
 
 fail:
 	pr_warn_ratelimited("failed to lookup one by real (%pd2, layer=%d, connected=%pd2, err=%i)\n",
 			    real, layer->idx, connected, err);
-	this = ERR_PTR(err);
-	goto out;
+	if (!IS_ERR(this))
+		dput(this);
+	return ERR_PTR(err);
 }
 
 static struct dentry *ovl_lookup_real(struct super_block *sb,
-- 
2.50.0.107.gf914562f5916.dirty

[PATCH v3 10/15] cachefiles: change cachefiles_bury_object to use start_renaming_dentry()

[NeilBrown]

From: NeilBrown <neil@brown.name>

Rather then using lock_rename() and lookup_one() etc we can use
the new start_renaming_dentry().  This is part of centralising dir
locking and lookup so that locking rules can be changed.

Some error check are removed as not necessary.  Checks for rep being a
non-dir or IS_DEADDIR and the check that ->graveyard is still a
directory only provide slightly more informative errors and have been
dropped.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
---
 fs/cachefiles/namei.c | 76 ++++++++-----------------------------------
 1 file changed, 14 insertions(+), 62 deletions(-)

diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index e5ec90dccc27..3af42ec78411 100644
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -270,7 +270,8 @@ int cachefiles_bury_object(struct cachefiles_cache *cache,
 			   struct dentry *rep,
 			   enum fscache_why_object_killed why)
 {
-	struct dentry *grave, *trap;
+	struct dentry *grave;
+	struct renamedata rd = {};
 	struct path path, path_to_graveyard;
 	char nbuffer[8 + 8 + 1];
 	int ret;
@@ -302,77 +303,36 @@ int cachefiles_bury_object(struct cachefiles_cache *cache,
 		(uint32_t) ktime_get_real_seconds(),
 		(uint32_t) atomic_inc_return(&cache->gravecounter));
 
-	/* do the multiway lock magic */
-	trap = lock_rename(cache->graveyard, dir);
-	if (IS_ERR(trap))
-		return PTR_ERR(trap);
-
-	/* do some checks before getting the grave dentry */
-	if (rep->d_parent != dir || IS_DEADDIR(d_inode(rep))) {
-		/* the entry was probably culled when we dropped the parent dir
-		 * lock */
-		unlock_rename(cache->graveyard, dir);
-		_leave(" = 0 [culled?]");
-		return 0;
-	}
-
-	if (!d_can_lookup(cache->graveyard)) {
-		unlock_rename(cache->graveyard, dir);
-		cachefiles_io_error(cache, "Graveyard no longer a directory");
-		return -EIO;
-	}
-
-	if (trap == rep) {
-		unlock_rename(cache->graveyard, dir);
-		cachefiles_io_error(cache, "May not make directory loop");
+	rd.mnt_idmap = &nop_mnt_idmap;
+	rd.old_parent = dir;
+	rd.new_parent = cache->graveyard;
+	rd.flags = 0;
+	ret = start_renaming_dentry(&rd, 0, rep, &QSTR(nbuffer));
+	if (ret) {
+		cachefiles_io_error(cache, "Cannot lock/lookup in graveyard");
 		return -EIO;
 	}
 
 	if (d_mountpoint(rep)) {
-		unlock_rename(cache->graveyard, dir);
+		end_renaming(&rd);
 		cachefiles_io_error(cache, "Mountpoint in cache");
 		return -EIO;
 	}
 
-	grave = lookup_one(&nop_mnt_idmap, &QSTR(nbuffer), cache->graveyard);
-	if (IS_ERR(grave)) {
-		unlock_rename(cache->graveyard, dir);
-		trace_cachefiles_vfs_error(object, d_inode(cache->graveyard),
-					   PTR_ERR(grave),
-					   cachefiles_trace_lookup_error);
-
-		if (PTR_ERR(grave) == -ENOMEM) {
-			_leave(" = -ENOMEM");
-			return -ENOMEM;
-		}
-
-		cachefiles_io_error(cache, "Lookup error %ld", PTR_ERR(grave));
-		return -EIO;
-	}
-
+	grave = rd.new_dentry;
 	if (d_is_positive(grave)) {
-		unlock_rename(cache->graveyard, dir);
-		dput(grave);
+		end_renaming(&rd);
 		grave = NULL;
 		cond_resched();
 		goto try_again;
 	}
 
 	if (d_mountpoint(grave)) {
-		unlock_rename(cache->graveyard, dir);
-		dput(grave);
+		end_renaming(&rd);
 		cachefiles_io_error(cache, "Mountpoint in graveyard");
 		return -EIO;
 	}
 
-	/* target should not be an ancestor of source */
-	if (trap == grave) {
-		unlock_rename(cache->graveyard, dir);
-		dput(grave);
-		cachefiles_io_error(cache, "May not make directory loop");
-		return -EIO;
-	}
-
 	/* attempt the rename */
 	path.mnt = cache->mnt;
 	path.dentry = dir;
@@ -382,13 +342,6 @@ int cachefiles_bury_object(struct cachefiles_cache *cache,
 	if (ret < 0) {
 		cachefiles_io_error(cache, "Rename security error %d", ret);
 	} else {
-		struct renamedata rd = {
-			.mnt_idmap	= &nop_mnt_idmap,
-			.old_parent	= dir,
-			.old_dentry	= rep,
-			.new_parent	= cache->graveyard,
-			.new_dentry	= grave,
-		};
 		trace_cachefiles_rename(object, d_inode(rep)->i_ino, why);
 		ret = cachefiles_inject_read_error();
 		if (ret == 0)
@@ -402,8 +355,7 @@ int cachefiles_bury_object(struct cachefiles_cache *cache,
 	}
 
 	__cachefiles_unmark_inode_in_use(object, d_inode(rep));
-	unlock_rename(cache->graveyard, dir);
-	dput(grave);
+	end_renaming(&rd);
 	_leave(" = 0");
 	return 0;
 }
-- 
2.50.0.107.gf914562f5916.dirty

[PATCH v3 11/15] ovl: pass name buffer to ovl_start_creating_temp()

[NeilBrown]

From: NeilBrown <neil@brown.name>

Now ovl_start_creating_temp() is passed a buffer in which to store the
temp name.  This will be useful in a future patch were ovl_create_real()
will need access to that name.

Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: NeilBrown <neil@brown.name>
---
 fs/overlayfs/dir.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index ff3dbd1ca61f..c4feb89ad1e3 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -66,10 +66,9 @@ void ovl_tempname(char name[OVL_TEMPNAME_SIZE])
 }
 
 static struct dentry *ovl_start_creating_temp(struct ovl_fs *ofs,
-					      struct dentry *workdir)
+					      struct dentry *workdir,
+					      char name[OVL_TEMPNAME_SIZE])
 {
-	char name[OVL_TEMPNAME_SIZE];
-
 	ovl_tempname(name);
 	return start_creating(ovl_upper_mnt_idmap(ofs), workdir,
 			      &QSTR(name));
@@ -81,11 +80,12 @@ static struct dentry *ovl_whiteout(struct ovl_fs *ofs)
 	struct dentry *whiteout, *link;
 	struct dentry *workdir = ofs->workdir;
 	struct inode *wdir = workdir->d_inode;
+	char name[OVL_TEMPNAME_SIZE];
 
 	guard(mutex)(&ofs->whiteout_lock);
 
 	if (!ofs->whiteout) {
-		whiteout = ovl_start_creating_temp(ofs, workdir);
+		whiteout = ovl_start_creating_temp(ofs, workdir, name);
 		if (IS_ERR(whiteout))
 			return whiteout;
 		err = ovl_do_whiteout(ofs, wdir, whiteout);
@@ -97,7 +97,7 @@ static struct dentry *ovl_whiteout(struct ovl_fs *ofs)
 	}
 
 	if (!ofs->no_shared_whiteout) {
-		link = ovl_start_creating_temp(ofs, workdir);
+		link = ovl_start_creating_temp(ofs, workdir, name);
 		if (IS_ERR(link))
 			return link;
 		err = ovl_do_link(ofs, ofs->whiteout, wdir, link);
@@ -247,7 +247,9 @@ struct dentry *ovl_create_temp(struct ovl_fs *ofs, struct dentry *workdir,
 			       struct ovl_cattr *attr)
 {
 	struct dentry *ret;
-	ret = ovl_start_creating_temp(ofs, workdir);
+	char name[OVL_TEMPNAME_SIZE];
+
+	ret = ovl_start_creating_temp(ofs, workdir, name);
 	if (IS_ERR(ret))
 		return ret;
 	ret = ovl_create_real(ofs, workdir, ret, attr);
-- 
2.50.0.107.gf914562f5916.dirty

[PATCH v3 12/15] ovl: change ovl_create_real() to get a new lock when re-opening created file.

[NeilBrown]

From: NeilBrown <neil@brown.name>

When ovl_create_real() is used to create a file on the upper filesystem
it needs to return the resulting dentry - positive and hashed.
It is usually the case the that dentry passed to the create function
(e.g.  vfs_create()) will be suitable but this is not guaranteed.  The
filesystem may unhash that dentry forcing a repeat lookup next time the
name is wanted.

So ovl_create_real() must be (and is) aware of this and prepared to
perform that lookup to get a hash positive dentry.

This is currently done under that same directory lock that provided
exclusion for the create.  Proposed changes to locking will make this
not possible - as the name, rather than the directory, will be locked.
The new APIs provided for lookup and locking do not and cannot support
this pattern.

The lock isn't needed.  ovl_create_real() can drop the lock and then get
a new lock for the lookup - then check that the lookup returned the
correct inode.  In a well-behaved configuration where the upper
filesystem is not being modified by a third party, this will always work
reliably, and if there are separate modification it will fail cleanly.

So change ovl_create_real() to drop the lock and call
ovl_start_creating_upper() to find the correct dentry.  Note that
start_creating doesn't fail if the name already exists.

The lookup previously used the name from newdentry which was guaranteed
to be stable because the parent directory was locked.  As we now drop
the lock we lose that guarantee.  As newdentry is unhashed it is
unlikely for the name to change, but safest not to depend on that.  So
the expected name is now passed in to ovl_create_real() and that is
used.

This removes the only remaining use of ovl_lookup_upper, so it is
removed.

Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: NeilBrown <neil@brown.name>
---
 fs/overlayfs/dir.c       | 37 +++++++++++++++++++++++++------------
 fs/overlayfs/overlayfs.h |  8 +-------
 fs/overlayfs/super.c     |  1 +
 3 files changed, 27 insertions(+), 19 deletions(-)

diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index c4feb89ad1e3..8c0a3d876fef 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -159,7 +159,8 @@ int ovl_cleanup_and_whiteout(struct ovl_fs *ofs, struct dentry *dir,
 }
 
 struct dentry *ovl_create_real(struct ovl_fs *ofs, struct dentry *parent,
-			       struct dentry *newdentry, struct ovl_cattr *attr)
+			       struct dentry *newdentry, struct qstr *qname,
+			       struct ovl_cattr *attr)
 {
 	struct inode *dir = parent->d_inode;
 	int err;
@@ -221,19 +222,30 @@ struct dentry *ovl_create_real(struct ovl_fs *ofs, struct dentry *parent,
 		struct dentry *d;
 		/*
 		 * Some filesystems (i.e. casefolded) may return an unhashed
-		 * negative dentry from the ovl_lookup_upper() call before
+		 * negative dentry from the ovl_start_creating_upper() call before
 		 * ovl_create_real().
 		 * In that case, lookup again after making the newdentry
 		 * positive, so ovl_create_upper() always returns a hashed
-		 * positive dentry.
+		 * positive dentry.  We lookup using qname which should be
+		 * the same name as newentry, but is certain not to change.
+		 * As we have to drop the lock before the lookup a race
+		 * could result in a lookup failure.  In that case we return
+		 * an error.
 		 */
-		d = ovl_lookup_upper(ofs, newdentry->d_name.name, parent,
-				     newdentry->d_name.len);
-		dput(newdentry);
-		if (IS_ERR_OR_NULL(d))
+		end_creating_keep(newdentry);
+		d = ovl_start_creating_upper(ofs, parent, qname);
+
+		if (IS_ERR_OR_NULL(d)) {
 			err = d ? PTR_ERR(d) : -ENOENT;
-		else
+		} else if (d->d_inode != newdentry->d_inode) {
+			err = -EIO;
+		} else {
+			dput(newdentry);
 			return d;
+		}
+		end_creating(d);
+		dput(newdentry);
+		return ERR_PTR(err);
 	}
 out:
 	if (err) {
@@ -252,7 +264,7 @@ struct dentry *ovl_create_temp(struct ovl_fs *ofs, struct dentry *workdir,
 	ret = ovl_start_creating_temp(ofs, workdir, name);
 	if (IS_ERR(ret))
 		return ret;
-	ret = ovl_create_real(ofs, workdir, ret, attr);
+	ret = ovl_create_real(ofs, workdir, ret, &QSTR(name), attr);
 	return end_creating_keep(ret);
 }
 
@@ -352,14 +364,15 @@ static int ovl_create_upper(struct dentry *dentry, struct inode *inode,
 	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 	struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 	struct dentry *newdentry;
+	struct qstr qname = QSTR_LEN(dentry->d_name.name,
+				     dentry->d_name.len);
 	int err;
 
 	newdentry = ovl_start_creating_upper(ofs, upperdir,
-					     &QSTR_LEN(dentry->d_name.name,
-						       dentry->d_name.len));
+					     &qname);
 	if (IS_ERR(newdentry))
 		return PTR_ERR(newdentry);
-	newdentry = ovl_create_real(ofs, upperdir, newdentry, attr);
+	newdentry = ovl_create_real(ofs, upperdir, newdentry, &qname, attr);
 	if (IS_ERR(newdentry))
 		return PTR_ERR(newdentry);
 
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index cad2055ebf18..714a1cec3709 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -406,13 +406,6 @@ static inline struct file *ovl_do_tmpfile(struct ovl_fs *ofs,
 	return file;
 }
 
-static inline struct dentry *ovl_lookup_upper(struct ovl_fs *ofs,
-					      const char *name,
-					      struct dentry *base, int len)
-{
-	return lookup_one(ovl_upper_mnt_idmap(ofs), &QSTR_LEN(name, len), base);
-}
-
 static inline struct dentry *ovl_lookup_upper_unlocked(struct ovl_fs *ofs,
 						       const char *name,
 						       struct dentry *base,
@@ -888,6 +881,7 @@ struct ovl_cattr {
 
 struct dentry *ovl_create_real(struct ovl_fs *ofs,
 			       struct dentry *parent, struct dentry *newdentry,
+			       struct qstr *qname,
 			       struct ovl_cattr *attr);
 int ovl_cleanup(struct ovl_fs *ofs, struct dentry *workdir, struct dentry *dentry);
 #define OVL_TEMPNAME_SIZE 20
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index d4c12feec039..109643930b9f 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -634,6 +634,7 @@ static struct dentry *ovl_lookup_or_create(struct ovl_fs *ofs,
 	if (!IS_ERR(child)) {
 		if (!child->d_inode)
 			child = ovl_create_real(ofs, parent, child,
+						&QSTR(name),
 						OVL_CATTR(mode));
 		end_creating_keep(child);
 	}
-- 
2.50.0.107.gf914562f5916.dirty

[PATCH v3 13/15] ovl: use is_subdir() for testing if one thing is a subdir of another

[NeilBrown]

From: NeilBrown <neil@brown.name>

Rather than using lock_rename(), use the more obvious is_subdir() for
ensuring that neither upper nor workdir contain the other.
Also be explicit in the comment that the two directories cannot be the
same.

As this is a point-it-time sanity check and does not provide any
on-going guarantees, the removal of locking does not introduce any
interesting races.

Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
---
 fs/overlayfs/super.c | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 109643930b9f..58adefb1c5b8 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -451,18 +451,13 @@ static int ovl_lower_dir(const char *name, const struct path *path,
 	return 0;
 }
 
-/* Workdir should not be subdir of upperdir and vice versa */
+/*
+ * Workdir should not be subdir of upperdir and vice versa, and
+ * they should not be the same.
+ */
 static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
 {
-	bool ok = false;
-
-	if (workdir != upperdir) {
-		struct dentry *trap = lock_rename(workdir, upperdir);
-		if (!IS_ERR(trap))
-			unlock_rename(workdir, upperdir);
-		ok = (trap == NULL);
-	}
-	return ok;
+	return !is_subdir(workdir, upperdir) && !is_subdir(upperdir, workdir);
 }
 
 static int ovl_setup_trap(struct super_block *sb, struct dentry *dir,
-- 
2.50.0.107.gf914562f5916.dirty

[PATCH v3 14/15] ovl: remove ovl_lock_rename_workdir()

[NeilBrown]

From: NeilBrown <neil@brown.name>

This function is unused since
   Commit 833d2b3a072f ("Add start_renaming_two_dentries()")

Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
---
 fs/overlayfs/overlayfs.h |  2 --
 fs/overlayfs/util.c      | 25 -------------------------
 2 files changed, 27 deletions(-)

diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 714a1cec3709..6fb99c583c31 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -569,8 +569,6 @@ bool ovl_is_inuse(struct dentry *dentry);
 bool ovl_need_index(struct dentry *dentry);
 int ovl_nlink_start(struct dentry *dentry);
 void ovl_nlink_end(struct dentry *dentry);
-int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *work,
-			    struct dentry *upperdir, struct dentry *upper);
 int ovl_check_metacopy_xattr(struct ovl_fs *ofs, const struct path *path,
 			     struct ovl_metacopy *data);
 int ovl_set_metacopy_xattr(struct ovl_fs *ofs, struct dentry *d,
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 3f1b763a8bb4..aa2a32793c2f 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -1213,31 +1213,6 @@ void ovl_nlink_end(struct dentry *dentry)
 	ovl_inode_unlock(inode);
 }
 
-int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *work,
-			    struct dentry *upperdir, struct dentry *upper)
-{
-	struct dentry *trap;
-
-	/* Workdir should not be subdir of upperdir and vice versa */
-	trap = lock_rename(workdir, upperdir);
-	if (IS_ERR(trap))
-		goto err;
-	if (trap)
-		goto err_unlock;
-	if (work && (work->d_parent != workdir || d_unhashed(work)))
-		goto err_unlock;
-	if (upper && (upper->d_parent != upperdir || d_unhashed(upper)))
-		goto err_unlock;
-
-	return 0;
-
-err_unlock:
-	unlock_rename(workdir, upperdir);
-err:
-	pr_err("failed to lock workdir+upperdir\n");
-	return -EIO;
-}
-
 /*
  * err < 0, 0 if no metacopy xattr, metacopy data size if xattr found.
  * an empty xattr returns OVL_METACOPY_MIN_SIZE to distinguish from no xattr value.
-- 
2.50.0.107.gf914562f5916.dirty

[PATCH v3 15/15] VFS: unexport lock_rename(), lock_rename_child(), unlock_rename()

[NeilBrown]

From: NeilBrown <neil@brown.name>

These three function are now only used in namei.c, so they don't need to
be exported.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
---
 Documentation/filesystems/porting.rst | 7 +++++++
 fs/namei.c                            | 9 +++------
 include/linux/namei.h                 | 3 ---
 3 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/Documentation/filesystems/porting.rst b/Documentation/filesystems/porting.rst
index 1dd31ab417a2..d02aa57e4477 100644
--- a/Documentation/filesystems/porting.rst
+++ b/Documentation/filesystems/porting.rst
@@ -1368,3 +1368,10 @@ lifetime, consider using inode_set_cached_link() instead.
 
 lookup_one_qstr_excl() is no longer exported - use start_creating() or
 similar.
+---
+
+** mandatory**
+
+lock_rename(), lock_rename_child(), unlock_rename() are no
+longer available.  Use start_renaming() or similar.
+
diff --git a/fs/namei.c b/fs/namei.c
index a5daa62399d7..77189335bbcc 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3775,7 +3775,7 @@ static struct dentry *lock_two_directories(struct dentry *p1, struct dentry *p2)
 /*
  * p1 and p2 should be directories on the same fs.
  */
-struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
+static struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
 {
 	if (p1 == p2) {
 		inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
@@ -3785,12 +3785,11 @@ struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
 	mutex_lock(&p1->d_sb->s_vfs_rename_mutex);
 	return lock_two_directories(p1, p2);
 }
-EXPORT_SYMBOL(lock_rename);
 
 /*
  * c1 and p2 should be on the same fs.
  */
-struct dentry *lock_rename_child(struct dentry *c1, struct dentry *p2)
+static struct dentry *lock_rename_child(struct dentry *c1, struct dentry *p2)
 {
 	if (READ_ONCE(c1->d_parent) == p2) {
 		/*
@@ -3827,9 +3826,8 @@ struct dentry *lock_rename_child(struct dentry *c1, struct dentry *p2)
 	mutex_unlock(&c1->d_sb->s_vfs_rename_mutex);
 	return NULL;
 }
-EXPORT_SYMBOL(lock_rename_child);
 
-void unlock_rename(struct dentry *p1, struct dentry *p2)
+static void unlock_rename(struct dentry *p1, struct dentry *p2)
 {
 	inode_unlock(p1->d_inode);
 	if (p1 != p2) {
@@ -3837,7 +3835,6 @@ void unlock_rename(struct dentry *p1, struct dentry *p2)
 		mutex_unlock(&p1->d_sb->s_vfs_rename_mutex);
 	}
 }
-EXPORT_SYMBOL(unlock_rename);
 
 /**
  * __start_renaming - lookup and lock names for rename
diff --git a/include/linux/namei.h b/include/linux/namei.h
index c7a7288cdd25..2ad6dd9987b9 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -165,9 +165,6 @@ extern int follow_down_one(struct path *);
 extern int follow_down(struct path *path, unsigned int flags);
 extern int follow_up(struct path *);
 
-extern struct dentry *lock_rename(struct dentry *, struct dentry *);
-extern struct dentry *lock_rename_child(struct dentry *, struct dentry *);
-extern void unlock_rename(struct dentry *, struct dentry *);
 int start_renaming(struct renamedata *rd, int lookup_flags,
 		   struct qstr *old_last, struct qstr *new_last);
 int start_renaming_dentry(struct renamedata *rd, int lookup_flags,
-- 
2.50.0.107.gf914562f5916.dirty

Re: [PATCH v3 01/15] VFS: note error returns in documentation for various lookup functions

[Jeff Layton]

On Wed, 2026-02-25 at 09:16 +1100, NeilBrown wrote:
> From: NeilBrown <neil@brown.name>
> 
> Darrick recently noted that try_lookup_noperm() is documented as
> "Look up a dentry by name in the dcache, returning NULL if it does not
> currently exist." but it can in fact return an error.
> 
> So update the documentation for that and related functions.
> 
> Link: https://lore.kernel.org/all/20260218234917.GA6490@frogsfrogsfrogs/
> Cc: "Darrick J. Wong" <djwong@kernel.org>
> Signed-off-by: NeilBrown <neil@brown.name>
> ---
>  fs/namei.c | 29 ++++++++++++++++++++++++++++-
>  1 file changed, 28 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/namei.c b/fs/namei.c
> index 58f715f7657e..6f595f58acfe 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -3124,7 +3124,8 @@ static int lookup_one_common(struct mnt_idmap *idmap,
>   * @base:	base directory to lookup from
>   *
>   * Look up a dentry by name in the dcache, returning NULL if it does not
> - * currently exist.  The function does not try to create a dentry and if one
> + * currently exist or an error if there is a problem with the name.
> + * The function does not try to create a dentry and if one
>   * is found it doesn't try to revalidate it.
>   *
>   * Note that this routine is purely a helper for filesystem usage and should
> @@ -3132,6 +3133,11 @@ static int lookup_one_common(struct mnt_idmap *idmap,
>   *
>   * No locks need be held - only a counted reference to @base is needed.
>   *
> + * Returns:
> + *   - ref-counted dentry on success, or
> + *   - %NULL if name could not be found, or
> + *   - ERR_PTR(-EACCES) if name is dot or dotdot or contains a slash or nul, or
> + *   - ERR_PTR() if fs provide ->d_hash, and this returned an error.
>   */
>  struct dentry *try_lookup_noperm(struct qstr *name, struct dentry *base)
>  {
> @@ -3208,6 +3214,11 @@ EXPORT_SYMBOL(lookup_one);
>   *
>   * Unlike lookup_one, it should be called without the parent
>   * i_rwsem held, and will take the i_rwsem itself if necessary.
> + *
> + * Returns: - A dentry, possibly negative, or
> + *	    - same errors as try_lookup_noperm() or
> + *	    - ERR_PTR(-ENOENT) if parent has been removed, or
> + *	    - ERR_PTR(-EACCES) if parent directory is not searchable.
>   */
>  struct dentry *lookup_one_unlocked(struct mnt_idmap *idmap, struct qstr *name,
>  				   struct dentry *base)
> @@ -3244,6 +3255,10 @@ EXPORT_SYMBOL(lookup_one_unlocked);
>   * It should be called without the parent i_rwsem held, and will take
>   * the i_rwsem itself if necessary.  If a fatal signal is pending or
>   * delivered, it will return %-EINTR if the lock is needed.
> + *
> + * Returns: A dentry, possibly negative, or
> + *	   - same errors as lookup_one_unlocked() or
> + *	   - ERR_PTR(-EINTR) if a fatal signal is pending.
>   */
>  struct dentry *lookup_one_positive_killable(struct mnt_idmap *idmap,
>  					    struct qstr *name,

Claude says:

  lookup_one_positive_killable() documentation says "A dentry, possibly negative" but the function
  explicitly converts negative dentries to ERR_PTR(-ENOENT). It should say "A positive dentry" like
  the companion functions lookup_one_positive_unlocked() and lookup_noperm_positive_unlocked().

...but that seems to be the only "regression" it found. 


Aside from that nit, this looks fine to me.

Reviewed-by: Jeff Layton <jlayton@kernel.org>

Re: [PATCH v3 04/15] libfs: change simple_done_creating() to use end_creating()

[Jeff Layton]

On Wed, 2026-02-25 at 09:16 +1100, NeilBrown wrote:
> From: NeilBrown <neil@brown.name>
> 
> simple_done_creating() and end_creating() are identical.
> So change the former to use the latter.  This further centralises
> unlocking of directories.
> 
> Signed-off-by: NeilBrown <neil@brown.name>
> ---
>  fs/libfs.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/fs/libfs.c b/fs/libfs.c
> index 74134ba2e8d1..63b4fb082435 100644
> --- a/fs/libfs.c
> +++ b/fs/libfs.c
> @@ -2318,7 +2318,6 @@ 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);
> +	end_creating(child);
>  }
>  EXPORT_SYMBOL(simple_done_creating);

Reviewed-by: Jeff Layton <jlayton@kernel.org>

Re: [PATCH v3 01/15] VFS: note error returns in documentation for various lookup functions

[NeilBrown]

On Tue, 03 Mar 2026, Jeff Layton wrote:
> On Wed, 2026-02-25 at 09:16 +1100, NeilBrown wrote:
> > From: NeilBrown <neil@brown.name>
> > 
> > Darrick recently noted that try_lookup_noperm() is documented as
> > "Look up a dentry by name in the dcache, returning NULL if it does not
> > currently exist." but it can in fact return an error.
> > 
> > So update the documentation for that and related functions.
> > 
> > Link: https://lore.kernel.org/all/20260218234917.GA6490@frogsfrogsfrogs/
> > Cc: "Darrick J. Wong" <djwong@kernel.org>
> > Signed-off-by: NeilBrown <neil@brown.name>
> > ---
> >  fs/namei.c | 29 ++++++++++++++++++++++++++++-
> >  1 file changed, 28 insertions(+), 1 deletion(-)
> > 
> > diff --git a/fs/namei.c b/fs/namei.c
> > index 58f715f7657e..6f595f58acfe 100644
> > --- a/fs/namei.c
> > +++ b/fs/namei.c
> > @@ -3124,7 +3124,8 @@ static int lookup_one_common(struct mnt_idmap *idmap,
> >   * @base:	base directory to lookup from
> >   *
> >   * Look up a dentry by name in the dcache, returning NULL if it does not
> > - * currently exist.  The function does not try to create a dentry and if one
> > + * currently exist or an error if there is a problem with the name.
> > + * The function does not try to create a dentry and if one
> >   * is found it doesn't try to revalidate it.
> >   *
> >   * Note that this routine is purely a helper for filesystem usage and should
> > @@ -3132,6 +3133,11 @@ static int lookup_one_common(struct mnt_idmap *idmap,
> >   *
> >   * No locks need be held - only a counted reference to @base is needed.
> >   *
> > + * Returns:
> > + *   - ref-counted dentry on success, or
> > + *   - %NULL if name could not be found, or
> > + *   - ERR_PTR(-EACCES) if name is dot or dotdot or contains a slash or nul, or
> > + *   - ERR_PTR() if fs provide ->d_hash, and this returned an error.
> >   */
> >  struct dentry *try_lookup_noperm(struct qstr *name, struct dentry *base)
> >  {
> > @@ -3208,6 +3214,11 @@ EXPORT_SYMBOL(lookup_one);
> >   *
> >   * Unlike lookup_one, it should be called without the parent
> >   * i_rwsem held, and will take the i_rwsem itself if necessary.
> > + *
> > + * Returns: - A dentry, possibly negative, or
> > + *	    - same errors as try_lookup_noperm() or
> > + *	    - ERR_PTR(-ENOENT) if parent has been removed, or
> > + *	    - ERR_PTR(-EACCES) if parent directory is not searchable.
> >   */
> >  struct dentry *lookup_one_unlocked(struct mnt_idmap *idmap, struct qstr *name,
> >  				   struct dentry *base)
> > @@ -3244,6 +3255,10 @@ EXPORT_SYMBOL(lookup_one_unlocked);
> >   * It should be called without the parent i_rwsem held, and will take
> >   * the i_rwsem itself if necessary.  If a fatal signal is pending or
> >   * delivered, it will return %-EINTR if the lock is needed.
> > + *
> > + * Returns: A dentry, possibly negative, or
> > + *	   - same errors as lookup_one_unlocked() or
> > + *	   - ERR_PTR(-EINTR) if a fatal signal is pending.
> >   */
> >  struct dentry *lookup_one_positive_killable(struct mnt_idmap *idmap,
> >  					    struct qstr *name,
> 
> Claude says:
> 
>   lookup_one_positive_killable() documentation says "A dentry, possibly negative" but the function
>   explicitly converts negative dentries to ERR_PTR(-ENOENT). It should say "A positive dentry" like
>   the companion functions lookup_one_positive_unlocked() and lookup_noperm_positive_unlocked().

Thanks.  The top patch in my next batch contains a bunch of similar
documentation cleanups.  I'll add this to that patch.

> 
> ...but that seems to be the only "regression" it found. 
> 

Good to know!

Thanks,
NeilBrown

> 
> Aside from that nit, this looks fine to me.
> 
> Reviewed-by: Jeff Layton <jlayton@kernel.org>
> 

Re: [PATCH v3 00/15] Further centralising of directory locking for name ops.

[NeilBrown]

Hi Christian,
 do you have thoughts about this series?  Any idea when you might have
 time to review and (hopefully) apply them?

Thanks,
NeilBrown


On Wed, 25 Feb 2026, NeilBrown wrote:
> Following Chris Mason's tool-based review, here is v3 with some fixes.
> Particularly 06/15 mistakenly tested the result of start_creating for NULL
> and 09/15 had some really messed up flow in error handling.
> Also human-language typos fixed.
> 
> This code is in 
>   github.com:neilbrown/linux.git
>   branch pdirops
> 
> For anyone interested, my next batch is in branch pdirops-next
> 
> Original patch description below.
> 
> Thanks,
> NeilBrown
> 
> I am working towards changing the locking rules for name-operations: locking
> the name rather than the whole directory.
> 
> The current part of this process is centralising all the locking so that
> it can be changed in one place.
> 
> Recently "start_creating", "start_removing", "start_renaming" and related
> interaces were added which combine the locking and the lookup.  At that time
> many callers were changed to use the new interfaces.  However there are still
> an assortment of places out side of fs/namei.c where the directory is locked
> explictly, whether with inode_lock() or lock_rename() or similar.  These were
> missed in the first pass for an assortment of uninteresting reasons.
> 
> This series addresses the remaining places where explicit locking is
> used, and changes them to use the new interfaces, or otherwise removes
> the explicit locking.
> 
> The biggest changes are in overlayfs.  The other changes are quite
> simple, though maybe the cachefiles changes is the least simple of those.
> 
> I'm running the --overlay tests in xfstests and nothing has popped yet.
> I'll continue with this and run some NFS tests too.
> 
> Thanks for your review of these patches!
> 
> NeilBrown
> 
>  [PATCH v3 01/15] VFS: note error returns in documentation for various
>  [PATCH v3 02/15] fs/proc: Don't lock root inode when creating "self"
>  [PATCH v3 03/15] VFS: move the start_dirop() kerndoc comment to
>  [PATCH v3 04/15] libfs: change simple_done_creating() to use
>  [PATCH v3 05/15] Apparmor: Use simple_start_creating() /
>  [PATCH v3 06/15] selinux: Use simple_start_creating() /
>  [PATCH v3 07/15] nfsd: switch purge_old() to use
>  [PATCH v3 08/15] VFS: make lookup_one_qstr_excl() static.
>  [PATCH v3 09/15] ovl: Simplify ovl_lookup_real_one()
>  [PATCH v3 10/15] cachefiles: change cachefiles_bury_object to use
>  [PATCH v3 11/15] ovl: pass name buffer to ovl_start_creating_temp()
>  [PATCH v3 12/15] ovl: change ovl_create_real() to get a new lock when
>  [PATCH v3 13/15] ovl: use is_subdir() for testing if one thing is a
>  [PATCH v3 14/15] ovl: remove ovl_lock_rename_workdir()
>  [PATCH v3 15/15] VFS: unexport lock_rename(), lock_rename_child(),
> 
> 

Re: [PATCH v3 05/15] Apparmor: Use simple_start_creating() / simple_done_creating()

[Christian Brauner]

On Wed, Feb 25, 2026 at 09:16:50AM +1100, NeilBrown wrote:
> From: NeilBrown <neil@brown.name>
> 
> Instead of explicitly locking the parent and performing a look up in
> apparmor, use simple_start_creating(), and then simple_done_creating()
> to unlock and drop the dentry.
> 
> This removes the need to check for an existing entry (as
> simple_start_creating() acts like an exclusive create and can return
> -EEXIST), simplifies error paths, and keeps dir locking code
> centralised.
> 
> Reviewed-by: Jeff Layton <jlayton@kernel.org>
> Signed-off-by: NeilBrown <neil@brown.name>
> ---

Fwiw, I think this fixes a reference count leak:

The old aafs_create returned dentries with refcount=2 (one from
lookup_noperm, one from dget in __aafs_setup_d_inode). The cleanup path
aafs_remove puts one reference leaving one reference that didn't get
cleaned up.

After your changes this is now correct as simple_done_creating() puts
the lookup reference.

Re: [PATCH v3 10/15] cachefiles: change cachefiles_bury_object to use start_renaming_dentry()

[Christian Brauner]

On Wed, Feb 25, 2026 at 09:16:55AM +1100, NeilBrown wrote:
> From: NeilBrown <neil@brown.name>
> 
> Rather then using lock_rename() and lookup_one() etc we can use
> the new start_renaming_dentry().  This is part of centralising dir
> locking and lookup so that locking rules can be changed.
> 
> Some error check are removed as not necessary.  Checks for rep being a
> non-dir or IS_DEADDIR and the check that ->graveyard is still a
> directory only provide slightly more informative errors and have been
> dropped.
> 
> Reviewed-by: Jeff Layton <jlayton@kernel.org>
> Signed-off-by: NeilBrown <neil@brown.name>
> ---
>  fs/cachefiles/namei.c | 76 ++++++++-----------------------------------
>  1 file changed, 14 insertions(+), 62 deletions(-)
> 
> diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
> index e5ec90dccc27..3af42ec78411 100644
> --- a/fs/cachefiles/namei.c
> +++ b/fs/cachefiles/namei.c
> @@ -270,7 +270,8 @@ int cachefiles_bury_object(struct cachefiles_cache *cache,
>  			   struct dentry *rep,
>  			   enum fscache_why_object_killed why)
>  {
> -	struct dentry *grave, *trap;
> +	struct dentry *grave;
> +	struct renamedata rd = {};
>  	struct path path, path_to_graveyard;
>  	char nbuffer[8 + 8 + 1];
>  	int ret;
> @@ -302,77 +303,36 @@ int cachefiles_bury_object(struct cachefiles_cache *cache,
>  		(uint32_t) ktime_get_real_seconds(),
>  		(uint32_t) atomic_inc_return(&cache->gravecounter));
>  
> -	/* do the multiway lock magic */
> -	trap = lock_rename(cache->graveyard, dir);
> -	if (IS_ERR(trap))
> -		return PTR_ERR(trap);
> -
> -	/* do some checks before getting the grave dentry */
> -	if (rep->d_parent != dir || IS_DEADDIR(d_inode(rep))) {
> -		/* the entry was probably culled when we dropped the parent dir
> -		 * lock */
> -		unlock_rename(cache->graveyard, dir);
> -		_leave(" = 0 [culled?]");
> -		return 0;

I think this is a subtle change in behavior?

If rep->d_parent != dir after lock_rename this returned 0 in the old
code. With your changes the same condition in __start_renaming_dentry
returns -EINVAL which means cachefiles_io_error() sets CACHEFILES_DEAD
and permanently disables the cache.

> -	}
> -
> -	if (!d_can_lookup(cache->graveyard)) {
> -		unlock_rename(cache->graveyard, dir);
> -		cachefiles_io_error(cache, "Graveyard no longer a directory");
> -		return -EIO;
> -	}
> -
> -	if (trap == rep) {
> -		unlock_rename(cache->graveyard, dir);
> -		cachefiles_io_error(cache, "May not make directory loop");
> +	rd.mnt_idmap = &nop_mnt_idmap;
> +	rd.old_parent = dir;
> +	rd.new_parent = cache->graveyard;
> +	rd.flags = 0;
> +	ret = start_renaming_dentry(&rd, 0, rep, &QSTR(nbuffer));
> +	if (ret) {
> +		cachefiles_io_error(cache, "Cannot lock/lookup in graveyard");
>  		return -EIO;
>  	}
>  
>  	if (d_mountpoint(rep)) {
> -		unlock_rename(cache->graveyard, dir);
> +		end_renaming(&rd);
>  		cachefiles_io_error(cache, "Mountpoint in cache");
>  		return -EIO;
>  	}
>  
> -	grave = lookup_one(&nop_mnt_idmap, &QSTR(nbuffer), cache->graveyard);
> -	if (IS_ERR(grave)) {
> -		unlock_rename(cache->graveyard, dir);
> -		trace_cachefiles_vfs_error(object, d_inode(cache->graveyard),
> -					   PTR_ERR(grave),
> -					   cachefiles_trace_lookup_error);
> -
> -		if (PTR_ERR(grave) == -ENOMEM) {
> -			_leave(" = -ENOMEM");
> -			return -ENOMEM;
> -		}

This too?

In the old code a -ENOMEM return from lookup_one() let the cache stay
alive and returned directly. The new code gets sent via
cachefiles_io_error() causing again CACHEFILES_DEAD to be set and
permanently disabling the cache.

Maybe both changes are intentional. If so we should probably note this
in the commit message or this should be fixed?

If you give me a fixup! on top of vfs-7.1.directory I can fold it.

Re: [PATCH v3 00/15] Further centralising of directory locking for name ops.

[Christian Brauner]

On Thu, Mar 05, 2026 at 12:24:38PM +1100, NeilBrown wrote:
> 
> Hi Christian,
>  do you have thoughts about this series?  Any idea when you might have
>  time to review and (hopefully) apply them?

Sorry, for the delay I picked it up but have two minor comments.

Re: [PATCH v3 05/15] Apparmor: Use simple_start_creating() / simple_done_creating()

[NeilBrown]

On Fri, 06 Mar 2026, Christian Brauner wrote:
> On Wed, Feb 25, 2026 at 09:16:50AM +1100, NeilBrown wrote:
> > From: NeilBrown <neil@brown.name>
> > 
> > Instead of explicitly locking the parent and performing a look up in
> > apparmor, use simple_start_creating(), and then simple_done_creating()
> > to unlock and drop the dentry.
> > 
> > This removes the need to check for an existing entry (as
> > simple_start_creating() acts like an exclusive create and can return
> > -EEXIST), simplifies error paths, and keeps dir locking code
> > centralised.
> > 
> > Reviewed-by: Jeff Layton <jlayton@kernel.org>
> > Signed-off-by: NeilBrown <neil@brown.name>
> > ---
> 
> Fwiw, I think this fixes a reference count leak:
> 
> The old aafs_create returned dentries with refcount=2 (one from
> lookup_noperm, one from dget in __aafs_setup_d_inode). The cleanup path
> aafs_remove puts one reference leaving one reference that didn't get
> cleaned up.
> 
> After your changes this is now correct as simple_done_creating() puts
> the lookup reference.
> 

Yes, I think you are correct.  I remember reviewing how ->dents was used
to confirm that the new refcounting was correct.  I didn't notice at the
time that the old was wrong.

Thanks,
NeilBrown

Re: [PATCH v3 00/15] Further centralising of directory locking for name ops.

[NeilBrown]

On Fri, 06 Mar 2026, Christian Brauner wrote:
> On Thu, Mar 05, 2026 at 12:24:38PM +1100, NeilBrown wrote:
> > 
> > Hi Christian,
> >  do you have thoughts about this series?  Any idea when you might have
> >  time to review and (hopefully) apply them?
> 
> Sorry, for the delay I picked it up but have two minor comments.
> 

Thanks!  I'll take a little while to examine the cachefiles code.
Thanks for the thorough review!

NeilBrown

[PATCH] FIXUP: cachefiles: change cachefiles_bury_object to use start_renaming_dentry()

[NeilBrown]

From: NeilBrown <neil@brown.name>

[[This fixup for f242581e611e in vfs/vfs-7.1.directory provides a new
commit description has preserves the error returns and log message, and
importantly calls cachefiles_io_error() in exactly the same
circumstances as the original - thanks]]

Rather then using lock_rename() and lookup_one() etc we can use
the new start_renaming_dentry().  This is part of centralising dir
locking and lookup so that locking rules can be changed.

Some error conditions are checked in start_renaming_dentry() but need to
be re-checked when an error is reported to ensure correct handling.
The check that ->graveyard is still d_can_lookup() is dropped as this
was checked when ->graveyard was assigned, and it cannot be changed.

Signed-off-by: NeilBrown <neil@brown.name>
Link: https://patch.msgid.link/20260224222542.3458677-11-neilb@ownmail.net
---
 fs/cachefiles/namei.c | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index 3af42ec78411..c464c72a51cb 100644
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -309,7 +309,26 @@ int cachefiles_bury_object(struct cachefiles_cache *cache,
 	rd.flags = 0;
 	ret = start_renaming_dentry(&rd, 0, rep, &QSTR(nbuffer));
 	if (ret) {
-		cachefiles_io_error(cache, "Cannot lock/lookup in graveyard");
+		/* Some errors aren't fatal */
+		if (ret == -EXDEV)
+			/* double-lock failed */
+			return ret;
+		if (d_unhashed(rep) || rep->d_parent != dir || IS_DEADDIR(d_inode(rep))) {
+			/* the entry was probably culled when we dropped the parent dir
+			 * lock */
+			_leave(" = 0 [culled?]");
+			return 0;
+		}
+		if (ret == -EINVAL || ret == -ENOTEMPTY) {
+			cachefiles_io_error(cache, "May not make directory loop");
+			return -EIO;
+		}
+		if (ret == -ENOMEM) {
+			_leave(" = -ENOMEM");
+			return -ENOMEM;
+		}
+
+		cachefiles_io_error(cache, "Lookup error %d", ret);
 		return -EIO;
 	}
 
-- 
2.50.0.107.gf914562f5916.dirty

Re: [PATCH] FIXUP: cachefiles: change cachefiles_bury_object to use start_renaming_dentry()

[Christian Brauner]

On Mon, 09 Mar 2026 07:57:58 +1100, NeilBrown wrote:
> [[This fixup for f242581e611e in vfs/vfs-7.1.directory provides a new
> commit description has preserves the error returns and log message, and
> importantly calls cachefiles_io_error() in exactly the same
> circumstances as the original - thanks]]
> 
> Rather then using lock_rename() and lookup_one() etc we can use
> the new start_renaming_dentry().  This is part of centralising dir
> locking and lookup so that locking rules can be changed.
> 
> [...]

Applied to the vfs-7.1.directory branch of the vfs/vfs.git tree.
Patches in the vfs-7.1.directory branch should appear in linux-next soon.

Please report any outstanding bugs that were missed during review in a
new review to the original patch series allowing us to drop it.

It's encouraged to provide Acked-bys and Reviewed-bys even though the
patch has now been applied. If possible patch trailers will be updated.

Note that commit hashes shown below are subject to change due to rebase,
trailer updates or similar. If in doubt, please check the listed branch.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
branch: vfs-7.1.directory

[1/1] FIXUP: cachefiles: change cachefiles_bury_object to use start_renaming_dentry()
      (fixup)