[PATCH v3 0/6] VFS: more prep for change to directory locking

[PATCH v3 0/6] VFS: more prep for change to directory locking

[NeilBrown]

This is a re-revised selection of cleanups and API renaming which continues
my work to centralise locking of create/remove/rename operations.

I've dropped the simple_end_creating etc changes which conflict with some of Al's work,
I've added a note to the first patch explaining that the linked list
does not need locking, and I've added a patch to rename start_creating() in debugfs
so the name can be used elsewhere in later patches.

Thanks,
NeilBrown

 [PATCH v3 1/6] VFS/ovl: add lookup_one_positive_killable()
 [PATCH v3 2/6] VFS: discard err2 in filename_create()
 [PATCH v3 3/6] VFS: unify old_mnt_idmap and new_mnt_idmap in
 [PATCH v3 4/6] VFS/audit: introduce kern_path_parent() for audit
 [PATCH v3 5/6] VFS: rename kern_path_locked() and related functions.
 [PATCH v3 6/6] debugfs: rename start_creating() to debugfs_start_creating()

[PATCH v3 1/6] VFS/ovl: add lookup_one_positive_killable()

[NeilBrown]

From: NeilBrown <neil@brown.name>

ovl wants a lookup which won't block on a fatal signal.  It currently
uses down_write_killable() and then repeatedly calls to lookup_one()

The lock may not be needed if the name is already in the dcache and it
aids proposed future changes if the locking is kept internal to namei.c

So this patch adds lookup_one_positive_killable() which is like
lookup_one_positive() but will abort in the face of a fatal signal.
overlayfs is changed to use this.

Note that instead of always getting an exclusive lock, ovl now only gets
a shared lock, and only sometimes.  The exclusive lock was never needed.

However down_read_killable() was only added in v4.15 but overlayfs started
using down_write_killable() here in v4.7.

Note that the linked list ->first_maybe_whiteout ->next_maybe_white is
local to the thread so there is no concurrency in that list which could
be threatened by removing the locking.

Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: NeilBrown <neil@brown.name>
---
 fs/namei.c             | 55 ++++++++++++++++++++++++++++++++++++++++++
 fs/overlayfs/readdir.c | 28 ++++++++++-----------
 include/linux/namei.h  |  3 +++
 3 files changed, 72 insertions(+), 14 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index cd43ff89fbaa..c7c6b255db2c 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1827,6 +1827,20 @@ static struct dentry *lookup_slow(const struct qstr *name,
 	return res;
 }
 
+static struct dentry *lookup_slow_killable(const struct qstr *name,
+					   struct dentry *dir,
+					   unsigned int flags)
+{
+	struct inode *inode = dir->d_inode;
+	struct dentry *res;
+
+	if (inode_lock_shared_killable(inode))
+		return ERR_PTR(-EINTR);
+	res = __lookup_slow(name, dir, flags);
+	inode_unlock_shared(inode);
+	return res;
+}
+
 static inline int may_lookup(struct mnt_idmap *idmap,
 			     struct nameidata *restrict nd)
 {
@@ -3010,6 +3024,47 @@ struct dentry *lookup_one_unlocked(struct mnt_idmap *idmap, struct qstr *name,
 }
 EXPORT_SYMBOL(lookup_one_unlocked);
 
+/**
+ * lookup_one_positive_killable - lookup single pathname component
+ * @idmap:	idmap of the mount the lookup is performed from
+ * @name:	qstr olding pathname component to lookup
+ * @base:	base directory to lookup from
+ *
+ * This helper will yield ERR_PTR(-ENOENT) on negatives. The helper returns
+ * known positive or ERR_PTR(). This is what most of the users want.
+ *
+ * Note that pinned negative with unlocked parent _can_ become positive at any
+ * time, so callers of lookup_one_unlocked() need to be very careful; pinned
+ * positives have >d_inode stable, so this one avoids such problems.
+ *
+ * This can be used for in-kernel filesystem clients such as file servers.
+ *
+ * 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.
+ */
+struct dentry *lookup_one_positive_killable(struct mnt_idmap *idmap,
+					    struct qstr *name,
+					    struct dentry *base)
+{
+	int err;
+	struct dentry *ret;
+
+	err = lookup_one_common(idmap, name, base);
+	if (err)
+		return ERR_PTR(err);
+
+	ret = lookup_dcache(name, base, 0);
+	if (!ret)
+		ret = lookup_slow_killable(name, base, 0);
+	if (!IS_ERR(ret) && d_flags_negative(smp_load_acquire(&ret->d_flags))) {
+		dput(ret);
+		ret = ERR_PTR(-ENOENT);
+	}
+	return ret;
+}
+EXPORT_SYMBOL(lookup_one_positive_killable);
+
 /**
  * lookup_one_positive_unlocked - lookup single pathname component
  * @idmap:	idmap of the mount the lookup is performed from
diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
index b65cdfce31ce..15cb06fa0c9a 100644
--- a/fs/overlayfs/readdir.c
+++ b/fs/overlayfs/readdir.c
@@ -270,26 +270,26 @@ static bool ovl_fill_merge(struct dir_context *ctx, const char *name,
 
 static int ovl_check_whiteouts(const struct path *path, struct ovl_readdir_data *rdd)
 {
-	int err;
+	int err = 0;
 	struct dentry *dentry, *dir = path->dentry;
 	const struct cred *old_cred;
 
 	old_cred = ovl_override_creds(rdd->dentry->d_sb);
 
-	err = down_write_killable(&dir->d_inode->i_rwsem);
-	if (!err) {
-		while (rdd->first_maybe_whiteout) {
-			struct ovl_cache_entry *p =
-				rdd->first_maybe_whiteout;
-			rdd->first_maybe_whiteout = p->next_maybe_whiteout;
-			dentry = lookup_one(mnt_idmap(path->mnt),
-					    &QSTR_LEN(p->name, p->len), dir);
-			if (!IS_ERR(dentry)) {
-				p->is_whiteout = ovl_is_whiteout(dentry);
-				dput(dentry);
-			}
+	while (rdd->first_maybe_whiteout) {
+		struct ovl_cache_entry *p =
+			rdd->first_maybe_whiteout;
+		rdd->first_maybe_whiteout = p->next_maybe_whiteout;
+		dentry = lookup_one_positive_killable(mnt_idmap(path->mnt),
+						      &QSTR_LEN(p->name, p->len),
+						      dir);
+		if (!IS_ERR(dentry)) {
+			p->is_whiteout = ovl_is_whiteout(dentry);
+			dput(dentry);
+		} else if (PTR_ERR(dentry) == -EINTR) {
+			err = -EINTR;
+			break;
 		}
-		inode_unlock(dir->d_inode);
 	}
 	ovl_revert_creds(old_cred);
 
diff --git a/include/linux/namei.h b/include/linux/namei.h
index 5d085428e471..551a1a01e5e7 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -80,6 +80,9 @@ struct dentry *lookup_one_unlocked(struct mnt_idmap *idmap,
 struct dentry *lookup_one_positive_unlocked(struct mnt_idmap *idmap,
 					    struct qstr *name,
 					    struct dentry *base);
+struct dentry *lookup_one_positive_killable(struct mnt_idmap *idmap,
+					    struct qstr *name,
+					    struct dentry *base);
 
 extern int follow_down_one(struct path *);
 extern int follow_down(struct path *path, unsigned int flags);
-- 
2.50.0.107.gf914562f5916.dirty

[PATCH v3 2/6] VFS: discard err2 in filename_create()

[NeilBrown]

From: NeilBrown <neil@brown.name>

Since 204a575e91f3 "VFS: add common error checks to lookup_one_qstr_excl()"
filename_create() does not need to stash the error value from mnt_want_write()
into a separate variable - the logic that used to clobber 'error' after the
call of mnt_want_write() has migrated into lookup_one_qstr_excl().

So there is no need for two different err variables.
This patch discards "err2" and uses "error' throughout.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
---
 fs/namei.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index c7c6b255db2c..e2c2ab286bc0 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4169,7 +4169,6 @@ static struct dentry *filename_create(int dfd, struct filename *name,
 	unsigned int reval_flag = lookup_flags & LOOKUP_REVAL;
 	unsigned int create_flags = LOOKUP_CREATE | LOOKUP_EXCL;
 	int type;
-	int err2;
 	int error;
 
 	error = filename_parentat(dfd, name, reval_flag, path, &last, &type);
@@ -4184,7 +4183,7 @@ static struct dentry *filename_create(int dfd, struct filename *name,
 		goto out;
 
 	/* don't fail immediately if it's r/o, at least try to report other errors */
-	err2 = mnt_want_write(path->mnt);
+	error = mnt_want_write(path->mnt);
 	/*
 	 * Do the final lookup.  Suppress 'create' if there is a trailing
 	 * '/', and a directory wasn't requested.
@@ -4197,17 +4196,16 @@ static struct dentry *filename_create(int dfd, struct filename *name,
 	if (IS_ERR(dentry))
 		goto unlock;
 
-	if (unlikely(err2)) {
-		error = err2;
+	if (unlikely(error))
 		goto fail;
-	}
+
 	return dentry;
 fail:
 	dput(dentry);
 	dentry = ERR_PTR(error);
 unlock:
 	inode_unlock(path->dentry->d_inode);
-	if (!err2)
+	if (!error)
 		mnt_drop_write(path->mnt);
 out:
 	path_put(path);
-- 
2.50.0.107.gf914562f5916.dirty

[PATCH v3 3/6] VFS: unify old_mnt_idmap and new_mnt_idmap in renamedata

[NeilBrown]

From: NeilBrown <neil@brown.name>

A rename operation can only rename within a single mount.  Callers of
vfs_rename() must and do ensure this is the case.

So there is no point in having two mnt_idmaps in renamedata as they are
always the same.  Only one of them is passed to ->rename in any case.

This patch replaces both with a single "mnt_idmap" and changes all
callers.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
---
 fs/cachefiles/namei.c    |  3 +--
 fs/ecryptfs/inode.c      |  3 +--
 fs/namei.c               | 17 ++++++++---------
 fs/nfsd/vfs.c            |  3 +--
 fs/overlayfs/overlayfs.h |  3 +--
 fs/smb/server/vfs.c      |  3 +--
 include/linux/fs.h       |  6 ++----
 7 files changed, 15 insertions(+), 23 deletions(-)

diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index 91dfd0231877..d1edb2ac3837 100644
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -387,10 +387,9 @@ int cachefiles_bury_object(struct cachefiles_cache *cache,
 		cachefiles_io_error(cache, "Rename security error %d", ret);
 	} else {
 		struct renamedata rd = {
-			.old_mnt_idmap	= &nop_mnt_idmap,
+			.mnt_idmap	= &nop_mnt_idmap,
 			.old_parent	= dir,
 			.old_dentry	= rep,
-			.new_mnt_idmap	= &nop_mnt_idmap,
 			.new_parent	= cache->graveyard,
 			.new_dentry	= grave,
 		};
diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index 72fbe1316ab8..abd954c6a14e 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -634,10 +634,9 @@ ecryptfs_rename(struct mnt_idmap *idmap, struct inode *old_dir,
 		goto out_lock;
 	}
 
-	rd.old_mnt_idmap	= &nop_mnt_idmap;
+	rd.mnt_idmap		= &nop_mnt_idmap;
 	rd.old_parent		= lower_old_dir_dentry;
 	rd.old_dentry		= lower_old_dentry;
-	rd.new_mnt_idmap	= &nop_mnt_idmap;
 	rd.new_parent		= lower_new_dir_dentry;
 	rd.new_dentry		= lower_new_dentry;
 	rc = vfs_rename(&rd);
diff --git a/fs/namei.c b/fs/namei.c
index e2c2ab286bc0..180037b96956 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -5077,20 +5077,20 @@ int vfs_rename(struct renamedata *rd)
 	if (source == target)
 		return 0;
 
-	error = may_delete(rd->old_mnt_idmap, old_dir, old_dentry, is_dir);
+	error = may_delete(rd->mnt_idmap, old_dir, old_dentry, is_dir);
 	if (error)
 		return error;
 
 	if (!target) {
-		error = may_create(rd->new_mnt_idmap, new_dir, new_dentry);
+		error = may_create(rd->mnt_idmap, new_dir, new_dentry);
 	} else {
 		new_is_dir = d_is_dir(new_dentry);
 
 		if (!(flags & RENAME_EXCHANGE))
-			error = may_delete(rd->new_mnt_idmap, new_dir,
+			error = may_delete(rd->mnt_idmap, new_dir,
 					   new_dentry, is_dir);
 		else
-			error = may_delete(rd->new_mnt_idmap, new_dir,
+			error = may_delete(rd->mnt_idmap, new_dir,
 					   new_dentry, new_is_dir);
 	}
 	if (error)
@@ -5105,13 +5105,13 @@ int vfs_rename(struct renamedata *rd)
 	 */
 	if (new_dir != old_dir) {
 		if (is_dir) {
-			error = inode_permission(rd->old_mnt_idmap, source,
+			error = inode_permission(rd->mnt_idmap, source,
 						 MAY_WRITE);
 			if (error)
 				return error;
 		}
 		if ((flags & RENAME_EXCHANGE) && new_is_dir) {
-			error = inode_permission(rd->new_mnt_idmap, target,
+			error = inode_permission(rd->mnt_idmap, target,
 						 MAY_WRITE);
 			if (error)
 				return error;
@@ -5179,7 +5179,7 @@ int vfs_rename(struct renamedata *rd)
 		if (error)
 			goto out;
 	}
-	error = old_dir->i_op->rename(rd->new_mnt_idmap, old_dir, old_dentry,
+	error = old_dir->i_op->rename(rd->mnt_idmap, old_dir, old_dentry,
 				      new_dir, new_dentry, flags);
 	if (error)
 		goto out;
@@ -5322,10 +5322,9 @@ int do_renameat2(int olddfd, struct filename *from, int newdfd,
 
 	rd.old_parent	   = old_path.dentry;
 	rd.old_dentry	   = old_dentry;
-	rd.old_mnt_idmap   = mnt_idmap(old_path.mnt);
+	rd.mnt_idmap	   = mnt_idmap(old_path.mnt);
 	rd.new_parent	   = new_path.dentry;
 	rd.new_dentry	   = new_dentry;
-	rd.new_mnt_idmap   = mnt_idmap(new_path.mnt);
 	rd.delegated_inode = &delegated_inode;
 	rd.flags	   = flags;
 	error = vfs_rename(&rd);
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index edf050766e57..aa4a95713a48 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1951,10 +1951,9 @@ nfsd_rename(struct svc_rqst *rqstp, struct svc_fh *ffhp, char *fname, int flen,
 		goto out_dput_old;
 	} else {
 		struct renamedata rd = {
-			.old_mnt_idmap	= &nop_mnt_idmap,
+			.mnt_idmap	= &nop_mnt_idmap,
 			.old_parent	= fdentry,
 			.old_dentry	= odentry,
-			.new_mnt_idmap	= &nop_mnt_idmap,
 			.new_parent	= tdentry,
 			.new_dentry	= ndentry,
 		};
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index bb0d7ded8e76..4f84abaa0d68 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -361,10 +361,9 @@ static inline int ovl_do_rename(struct ovl_fs *ofs, struct dentry *olddir,
 {
 	int err;
 	struct renamedata rd = {
-		.old_mnt_idmap	= ovl_upper_mnt_idmap(ofs),
+		.mnt_idmap	= ovl_upper_mnt_idmap(ofs),
 		.old_parent	= olddir,
 		.old_dentry	= olddentry,
-		.new_mnt_idmap	= ovl_upper_mnt_idmap(ofs),
 		.new_parent	= newdir,
 		.new_dentry	= newdentry,
 		.flags		= flags,
diff --git a/fs/smb/server/vfs.c b/fs/smb/server/vfs.c
index 04539037108c..07739055ac9f 100644
--- a/fs/smb/server/vfs.c
+++ b/fs/smb/server/vfs.c
@@ -770,10 +770,9 @@ int ksmbd_vfs_rename(struct ksmbd_work *work, const struct path *old_path,
 		goto out4;
 	}
 
-	rd.old_mnt_idmap	= mnt_idmap(old_path->mnt),
+	rd.mnt_idmap		= mnt_idmap(old_path->mnt),
 	rd.old_parent		= old_parent,
 	rd.old_dentry		= old_child,
-	rd.new_mnt_idmap	= mnt_idmap(new_path.mnt),
 	rd.new_parent		= new_path.dentry,
 	rd.new_dentry		= new_dentry,
 	rd.flags		= flags,
diff --git a/include/linux/fs.h b/include/linux/fs.h
index d7ab4f96d705..73b39e5bb9e4 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2008,20 +2008,18 @@ int vfs_unlink(struct mnt_idmap *, struct inode *, struct dentry *,
 
 /**
  * struct renamedata - contains all information required for renaming
- * @old_mnt_idmap:     idmap of the old mount the inode was found from
+ * @mnt_idmap:     idmap of the mount in which the rename is happening.
  * @old_parent:        parent of source
  * @old_dentry:                source
- * @new_mnt_idmap:     idmap of the new mount the inode was found from
  * @new_parent:        parent of destination
  * @new_dentry:                destination
  * @delegated_inode:   returns an inode needing a delegation break
  * @flags:             rename flags
  */
 struct renamedata {
-	struct mnt_idmap *old_mnt_idmap;
+	struct mnt_idmap *mnt_idmap;
 	struct dentry *old_parent;
 	struct dentry *old_dentry;
-	struct mnt_idmap *new_mnt_idmap;
 	struct dentry *new_parent;
 	struct dentry *new_dentry;
 	struct inode **delegated_inode;
-- 
2.50.0.107.gf914562f5916.dirty

[PATCH v3 4/6] VFS/audit: introduce kern_path_parent() for audit

[NeilBrown]

From: NeilBrown <neil@brown.name>

audit_alloc_mark() and audit_get_nd() both need to perform a path
lookup getting the parent dentry (which must exist) and the final
target (following a LAST_NORM name) which sometimes doesn't need to
exist.

They don't need the parent to be locked, but use kern_path_locked() or
kern_path_locked_negative() anyway.  This is somewhat misleading to the
casual reader.

This patch introduces a more targeted function, kern_path_parent(),
which returns not holding locks.  On success the "path" will
be set to the parent, which must be found, and the return value is the
dentry of the target, which might be negative.

This will clear the way to rename kern_path_locked() which is
otherwise only used to prepare for removing something.

It also allows us to remove kern_path_locked_negative(), which is
transformed into the new kern_path_parent().

Signed-off-by: NeilBrown <neil@brown.name>
---
 fs/namei.c              | 23 +++++++++++++++++------
 include/linux/namei.h   |  2 +-
 kernel/audit_fsnotify.c | 11 ++++++-----
 kernel/audit_watch.c    |  3 +--
 4 files changed, 25 insertions(+), 14 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 180037b96956..4017bc8641d3 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2781,7 +2781,20 @@ static struct dentry *__kern_path_locked(int dfd, struct filename *name, struct
 	return d;
 }
 
-struct dentry *kern_path_locked_negative(const char *name, struct path *path)
+/**
+ * kern_path_parent: lookup path returning parent and target
+ * @name: path name
+ * @path: path to store parent in
+ *
+ * The path @name should end with a normal component, not "." or ".." or "/".
+ * A lookup is performed and if successful the parent information
+ * is store in @parent and the dentry is returned.
+ *
+ * The dentry maybe negative, the parent will be positive.
+ *
+ * Returns:  dentry or error.
+ */
+struct dentry *kern_path_parent(const char *name, struct path *path)
 {
 	struct path parent_path __free(path_put) = {};
 	struct filename *filename __free(putname) = getname_kernel(name);
@@ -2794,12 +2807,10 @@ struct dentry *kern_path_locked_negative(const char *name, struct path *path)
 		return ERR_PTR(error);
 	if (unlikely(type != LAST_NORM))
 		return ERR_PTR(-EINVAL);
-	inode_lock_nested(parent_path.dentry->d_inode, I_MUTEX_PARENT);
-	d = lookup_one_qstr_excl(&last, parent_path.dentry, LOOKUP_CREATE);
-	if (IS_ERR(d)) {
-		inode_unlock(parent_path.dentry->d_inode);
+
+	d = lookup_noperm_unlocked(&last, parent_path.dentry);
+	if (IS_ERR(d))
 		return d;
-	}
 	path->dentry = no_free_ptr(parent_path.dentry);
 	path->mnt = no_free_ptr(parent_path.mnt);
 	return d;
diff --git a/include/linux/namei.h b/include/linux/namei.h
index 551a1a01e5e7..1d5038c21c20 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -57,12 +57,12 @@ 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);
 
 extern struct dentry *kern_path_create(int, const char *, struct path *, unsigned int);
 extern struct dentry *user_path_create(int, const char __user *, struct path *, unsigned int);
 extern void done_path_create(struct path *, struct dentry *);
 extern struct dentry *kern_path_locked(const char *, struct path *);
-extern struct dentry *kern_path_locked_negative(const char *, struct path *);
 extern struct dentry *user_path_locked_at(int , const char __user *, struct path *);
 int vfs_path_parent_lookup(struct filename *filename, unsigned int flags,
 			   struct path *parent, struct qstr *last, int *type,
diff --git a/kernel/audit_fsnotify.c b/kernel/audit_fsnotify.c
index c565fbf66ac8..b92805b317a2 100644
--- a/kernel/audit_fsnotify.c
+++ b/kernel/audit_fsnotify.c
@@ -76,17 +76,18 @@ struct audit_fsnotify_mark *audit_alloc_mark(struct audit_krule *krule, char *pa
 	struct audit_fsnotify_mark *audit_mark;
 	struct path path;
 	struct dentry *dentry;
-	struct inode *inode;
 	int ret;
 
 	if (pathname[0] != '/' || pathname[len-1] == '/')
 		return ERR_PTR(-EINVAL);
 
-	dentry = kern_path_locked(pathname, &path);
+	dentry = kern_path_parent(pathname, &path);
 	if (IS_ERR(dentry))
 		return ERR_CAST(dentry); /* returning an error */
-	inode = path.dentry->d_inode;
-	inode_unlock(inode);
+	if (d_really_is_negative(dentry)) {
+		audit_mark = ERR_PTR(-ENOENT);
+		goto out;
+	}
 
 	audit_mark = kzalloc(sizeof(*audit_mark), GFP_KERNEL);
 	if (unlikely(!audit_mark)) {
@@ -100,7 +101,7 @@ struct audit_fsnotify_mark *audit_alloc_mark(struct audit_krule *krule, char *pa
 	audit_update_mark(audit_mark, dentry->d_inode);
 	audit_mark->rule = krule;
 
-	ret = fsnotify_add_inode_mark(&audit_mark->mark, inode, 0);
+	ret = fsnotify_add_inode_mark(&audit_mark->mark, path.dentry->d_inode, 0);
 	if (ret < 0) {
 		audit_mark->path = NULL;
 		fsnotify_put_mark(&audit_mark->mark);
diff --git a/kernel/audit_watch.c b/kernel/audit_watch.c
index 0ebbbe37a60f..a700e3c8925f 100644
--- a/kernel/audit_watch.c
+++ b/kernel/audit_watch.c
@@ -349,7 +349,7 @@ static int audit_get_nd(struct audit_watch *watch, struct path *parent)
 {
 	struct dentry *d;
 
-	d = kern_path_locked_negative(watch->path, parent);
+	d = kern_path_parent(watch->path, parent);
 	if (IS_ERR(d))
 		return PTR_ERR(d);
 
@@ -359,7 +359,6 @@ static int audit_get_nd(struct audit_watch *watch, struct path *parent)
 		watch->ino = d_backing_inode(d)->i_ino;
 	}
 
-	inode_unlock(d_backing_inode(parent->dentry));
 	dput(d);
 	return 0;
 }
-- 
2.50.0.107.gf914562f5916.dirty

[PATCH v3 5/6] VFS: rename kern_path_locked() and related functions.

[NeilBrown]

From: NeilBrown <neil@brown.name>

kern_path_locked() is now only used to prepare for removing an object
from the filesystem (and that is the only credible reason for wanting a
positive locked dentry).  Thus it corresponds to kern_path_create() and
so should have a corresponding name.

Unfortunately the name "kern_path_create" is somewhat misleading as it
doesn't actually create anything.  The recently added
simple_start_creating() provides a better pattern I believe.  The
"start" can be matched with "end" to bracket the creating or removing.

So this patch changes names:

 kern_path_locked -> start_removing_path
 kern_path_create -> start_creating_path
 user_path_create -> start_creating_user_path
 user_path_locked_at -> start_removing_user_path_at
 done_path_create -> end_creating_path

and also introduces end_removing_path() which is identical to
end_creating_path().

__start_removing_path (which was __kern_path_locked) is enhanced to
call mnt_want_write() for consistency with the start_creating_path().

Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: NeilBrown <neil@brown.name>
---
 Documentation/filesystems/porting.rst        | 12 ++++
 arch/powerpc/platforms/cell/spufs/syscalls.c |  4 +-
 drivers/base/devtmpfs.c                      | 22 +++-----
 fs/bcachefs/fs-ioctl.c                       | 10 ++--
 fs/init.c                                    | 17 +++---
 fs/namei.c                                   | 59 ++++++++++++--------
 fs/ocfs2/refcounttree.c                      |  4 +-
 fs/smb/server/vfs.c                          |  8 +--
 include/linux/namei.h                        | 14 +++--
 kernel/bpf/inode.c                           |  4 +-
 net/unix/af_unix.c                           |  6 +-
 11 files changed, 93 insertions(+), 67 deletions(-)

diff --git a/Documentation/filesystems/porting.rst b/Documentation/filesystems/porting.rst
index 85f590254f07..e0494860be6b 100644
--- a/Documentation/filesystems/porting.rst
+++ b/Documentation/filesystems/porting.rst
@@ -1285,3 +1285,15 @@ rather than a VMA, as the VMA at this stage is not yet valid.
 The vm_area_desc provides the minimum required information for a filesystem
 to initialise state upon memory mapping of a file-backed region, and output
 parameters for the file system to set this state.
+
+---
+
+**mandatory**
+
+Several functions are renamed:
+
+-  kern_path_locked -> start_removing_path
+-  kern_path_create -> start_creating_path
+-  user_path_create -> start_creating_user_path
+-  user_path_locked_at -> start_removing_user_path_at
+-  done_path_create -> end_creating_path
diff --git a/arch/powerpc/platforms/cell/spufs/syscalls.c b/arch/powerpc/platforms/cell/spufs/syscalls.c
index 157e046e6e93..ea4ba1b6ce6a 100644
--- a/arch/powerpc/platforms/cell/spufs/syscalls.c
+++ b/arch/powerpc/platforms/cell/spufs/syscalls.c
@@ -67,11 +67,11 @@ static long do_spu_create(const char __user *pathname, unsigned int flags,
 	struct dentry *dentry;
 	int ret;
 
-	dentry = user_path_create(AT_FDCWD, pathname, &path, LOOKUP_DIRECTORY);
+	dentry = start_creating_user_path(AT_FDCWD, pathname, &path, LOOKUP_DIRECTORY);
 	ret = PTR_ERR(dentry);
 	if (!IS_ERR(dentry)) {
 		ret = spufs_create(&path, dentry, flags, mode, neighbor);
-		done_path_create(&path, dentry);
+		end_creating_path(&path, dentry);
 	}
 
 	return ret;
diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
index 31bfb3194b4c..9d4e46ad8352 100644
--- a/drivers/base/devtmpfs.c
+++ b/drivers/base/devtmpfs.c
@@ -176,7 +176,7 @@ static int dev_mkdir(const char *name, umode_t mode)
 	struct dentry *dentry;
 	struct path path;
 
-	dentry = kern_path_create(AT_FDCWD, name, &path, LOOKUP_DIRECTORY);
+	dentry = start_creating_path(AT_FDCWD, name, &path, LOOKUP_DIRECTORY);
 	if (IS_ERR(dentry))
 		return PTR_ERR(dentry);
 
@@ -184,7 +184,7 @@ static int dev_mkdir(const char *name, umode_t mode)
 	if (!IS_ERR(dentry))
 		/* mark as kernel-created inode */
 		d_inode(dentry)->i_private = &thread;
-	done_path_create(&path, dentry);
+	end_creating_path(&path, dentry);
 	return PTR_ERR_OR_ZERO(dentry);
 }
 
@@ -222,10 +222,10 @@ static int handle_create(const char *nodename, umode_t mode, kuid_t uid,
 	struct path path;
 	int err;
 
-	dentry = kern_path_create(AT_FDCWD, nodename, &path, 0);
+	dentry = start_creating_path(AT_FDCWD, nodename, &path, 0);
 	if (dentry == ERR_PTR(-ENOENT)) {
 		create_path(nodename);
-		dentry = kern_path_create(AT_FDCWD, nodename, &path, 0);
+		dentry = start_creating_path(AT_FDCWD, nodename, &path, 0);
 	}
 	if (IS_ERR(dentry))
 		return PTR_ERR(dentry);
@@ -246,7 +246,7 @@ static int handle_create(const char *nodename, umode_t mode, kuid_t uid,
 		/* mark as kernel-created inode */
 		d_inode(dentry)->i_private = &thread;
 	}
-	done_path_create(&path, dentry);
+	end_creating_path(&path, dentry);
 	return err;
 }
 
@@ -256,7 +256,7 @@ static int dev_rmdir(const char *name)
 	struct dentry *dentry;
 	int err;
 
-	dentry = kern_path_locked(name, &parent);
+	dentry = start_removing_path(name, &parent);
 	if (IS_ERR(dentry))
 		return PTR_ERR(dentry);
 	if (d_inode(dentry)->i_private == &thread)
@@ -265,9 +265,7 @@ static int dev_rmdir(const char *name)
 	else
 		err = -EPERM;
 
-	dput(dentry);
-	inode_unlock(d_inode(parent.dentry));
-	path_put(&parent);
+	end_removing_path(&parent, dentry);
 	return err;
 }
 
@@ -325,7 +323,7 @@ static int handle_remove(const char *nodename, struct device *dev)
 	int deleted = 0;
 	int err = 0;
 
-	dentry = kern_path_locked(nodename, &parent);
+	dentry = start_removing_path(nodename, &parent);
 	if (IS_ERR(dentry))
 		return PTR_ERR(dentry);
 
@@ -349,10 +347,8 @@ static int handle_remove(const char *nodename, struct device *dev)
 		if (!err || err == -ENOENT)
 			deleted = 1;
 	}
-	dput(dentry);
-	inode_unlock(d_inode(parent.dentry));
+	end_removing_path(&parent, dentry);
 
-	path_put(&parent);
 	if (deleted && strchr(nodename, '/'))
 		delete_path(nodename);
 	return err;
diff --git a/fs/bcachefs/fs-ioctl.c b/fs/bcachefs/fs-ioctl.c
index 4e72e654da96..43510da5e734 100644
--- a/fs/bcachefs/fs-ioctl.c
+++ b/fs/bcachefs/fs-ioctl.c
@@ -255,7 +255,7 @@ static long bch2_ioctl_subvolume_create(struct bch_fs *c, struct file *filp,
 		snapshot_src = inode_inum(to_bch_ei(src_path.dentry->d_inode));
 	}
 
-	dst_dentry = user_path_create(arg.dirfd,
+	dst_dentry = start_creating_user_path(arg.dirfd,
 			(const char __user *)(unsigned long)arg.dst_ptr,
 			&dst_path, lookup_flags);
 	error = PTR_ERR_OR_ZERO(dst_dentry);
@@ -314,7 +314,7 @@ static long bch2_ioctl_subvolume_create(struct bch_fs *c, struct file *filp,
 	d_instantiate(dst_dentry, &inode->v);
 	fsnotify_mkdir(dir, dst_dentry);
 err3:
-	done_path_create(&dst_path, dst_dentry);
+	end_creating_path(&dst_path, dst_dentry);
 err2:
 	if (arg.src_ptr)
 		path_put(&src_path);
@@ -334,7 +334,7 @@ static long bch2_ioctl_subvolume_destroy(struct bch_fs *c, struct file *filp,
 	if (arg.flags)
 		return -EINVAL;
 
-	victim = user_path_locked_at(arg.dirfd, name, &path);
+	victim = start_removing_user_path_at(arg.dirfd, name, &path);
 	if (IS_ERR(victim))
 		return PTR_ERR(victim);
 
@@ -351,9 +351,7 @@ static long bch2_ioctl_subvolume_destroy(struct bch_fs *c, struct file *filp,
 		d_invalidate(victim);
 	}
 err:
-	inode_unlock(dir);
-	dput(victim);
-	path_put(&path);
+	end_removing_path(&path, victim);
 	return ret;
 }
 
diff --git a/fs/init.c b/fs/init.c
index eef5124885e3..07f592ccdba8 100644
--- a/fs/init.c
+++ b/fs/init.c
@@ -149,7 +149,7 @@ int __init init_mknod(const char *filename, umode_t mode, unsigned int dev)
 	else if (!(S_ISBLK(mode) || S_ISCHR(mode)))
 		return -EINVAL;
 
-	dentry = kern_path_create(AT_FDCWD, filename, &path, 0);
+	dentry = start_creating_path(AT_FDCWD, filename, &path, 0);
 	if (IS_ERR(dentry))
 		return PTR_ERR(dentry);
 
@@ -158,7 +158,7 @@ int __init init_mknod(const char *filename, umode_t mode, unsigned int dev)
 	if (!error)
 		error = vfs_mknod(mnt_idmap(path.mnt), path.dentry->d_inode,
 				  dentry, mode, new_decode_dev(dev));
-	done_path_create(&path, dentry);
+	end_creating_path(&path, dentry);
 	return error;
 }
 
@@ -173,7 +173,7 @@ int __init init_link(const char *oldname, const char *newname)
 	if (error)
 		return error;
 
-	new_dentry = kern_path_create(AT_FDCWD, newname, &new_path, 0);
+	new_dentry = start_creating_path(AT_FDCWD, newname, &new_path, 0);
 	error = PTR_ERR(new_dentry);
 	if (IS_ERR(new_dentry))
 		goto out;
@@ -191,7 +191,7 @@ int __init init_link(const char *oldname, const char *newname)
 	error = vfs_link(old_path.dentry, idmap, new_path.dentry->d_inode,
 			 new_dentry, NULL);
 out_dput:
-	done_path_create(&new_path, new_dentry);
+	end_creating_path(&new_path, new_dentry);
 out:
 	path_put(&old_path);
 	return error;
@@ -203,14 +203,14 @@ int __init init_symlink(const char *oldname, const char *newname)
 	struct path path;
 	int error;
 
-	dentry = kern_path_create(AT_FDCWD, newname, &path, 0);
+	dentry = start_creating_path(AT_FDCWD, newname, &path, 0);
 	if (IS_ERR(dentry))
 		return PTR_ERR(dentry);
 	error = security_path_symlink(&path, dentry, oldname);
 	if (!error)
 		error = vfs_symlink(mnt_idmap(path.mnt), path.dentry->d_inode,
 				    dentry, oldname);
-	done_path_create(&path, dentry);
+	end_creating_path(&path, dentry);
 	return error;
 }
 
@@ -225,7 +225,8 @@ int __init init_mkdir(const char *pathname, umode_t mode)
 	struct path path;
 	int error;
 
-	dentry = kern_path_create(AT_FDCWD, pathname, &path, LOOKUP_DIRECTORY);
+	dentry = start_creating_path(AT_FDCWD, pathname, &path,
+				     LOOKUP_DIRECTORY);
 	if (IS_ERR(dentry))
 		return PTR_ERR(dentry);
 	mode = mode_strip_umask(d_inode(path.dentry), mode);
@@ -236,7 +237,7 @@ int __init init_mkdir(const char *pathname, umode_t mode)
 		if (IS_ERR(dentry))
 			error = PTR_ERR(dentry);
 	}
-	done_path_create(&path, dentry);
+	end_creating_path(&path, dentry);
 	return error;
 }
 
diff --git a/fs/namei.c b/fs/namei.c
index 4017bc8641d3..5ceb971632fe 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2758,7 +2758,8 @@ static int filename_parentat(int dfd, struct filename *name,
 }
 
 /* does lookup, returns the object with parent locked */
-static struct dentry *__kern_path_locked(int dfd, struct filename *name, struct path *path)
+static struct dentry *__start_removing_path(int dfd, struct filename *name,
+					   struct path *path)
 {
 	struct path parent_path __free(path_put) = {};
 	struct dentry *d;
@@ -2770,15 +2771,26 @@ static struct dentry *__kern_path_locked(int dfd, struct filename *name, struct
 		return ERR_PTR(error);
 	if (unlikely(type != LAST_NORM))
 		return ERR_PTR(-EINVAL);
+	/* don't fail immediately if it's r/o, at least try to report other errors */
+	error = mnt_want_write(path->mnt);
 	inode_lock_nested(parent_path.dentry->d_inode, I_MUTEX_PARENT);
 	d = lookup_one_qstr_excl(&last, parent_path.dentry, 0);
-	if (IS_ERR(d)) {
-		inode_unlock(parent_path.dentry->d_inode);
-		return d;
-	}
+	if (IS_ERR(d))
+		goto unlock;
+	if (error)
+		goto fail;
 	path->dentry = no_free_ptr(parent_path.dentry);
 	path->mnt = no_free_ptr(parent_path.mnt);
 	return d;
+
+fail:
+	dput(d);
+	d = ERR_PTR(error);
+unlock:
+	inode_unlock(parent_path.dentry->d_inode);
+	if (!error)
+		mnt_drop_write(path->mnt);
+	return d;
 }
 
 /**
@@ -2816,24 +2828,26 @@ struct dentry *kern_path_parent(const char *name, struct path *path)
 	return d;
 }
 
-struct dentry *kern_path_locked(const char *name, struct path *path)
+struct dentry *start_removing_path(const char *name, struct path *path)
 {
 	struct filename *filename = getname_kernel(name);
-	struct dentry *res = __kern_path_locked(AT_FDCWD, filename, path);
+	struct dentry *res = __start_removing_path(AT_FDCWD, filename, path);
 
 	putname(filename);
 	return res;
 }
 
-struct dentry *user_path_locked_at(int dfd, const char __user *name, struct path *path)
+struct dentry *start_removing_user_path_at(int dfd,
+					   const char __user *name,
+					   struct path *path)
 {
 	struct filename *filename = getname(name);
-	struct dentry *res = __kern_path_locked(dfd, filename, path);
+	struct dentry *res = __start_removing_path(dfd, filename, path);
 
 	putname(filename);
 	return res;
 }
-EXPORT_SYMBOL(user_path_locked_at);
+EXPORT_SYMBOL(start_removing_user_path_at);
 
 int kern_path(const char *name, unsigned int flags, struct path *path)
 {
@@ -4223,8 +4237,8 @@ static struct dentry *filename_create(int dfd, struct filename *name,
 	return dentry;
 }
 
-struct dentry *kern_path_create(int dfd, const char *pathname,
-				struct path *path, unsigned int lookup_flags)
+struct dentry *start_creating_path(int dfd, const char *pathname,
+				   struct path *path, unsigned int lookup_flags)
 {
 	struct filename *filename = getname_kernel(pathname);
 	struct dentry *res = filename_create(dfd, filename, path, lookup_flags);
@@ -4232,9 +4246,9 @@ struct dentry *kern_path_create(int dfd, const char *pathname,
 	putname(filename);
 	return res;
 }
-EXPORT_SYMBOL(kern_path_create);
+EXPORT_SYMBOL(start_creating_path);
 
-void done_path_create(struct path *path, struct dentry *dentry)
+void end_creating_path(struct path *path, struct dentry *dentry)
 {
 	if (!IS_ERR(dentry))
 		dput(dentry);
@@ -4242,10 +4256,11 @@ void done_path_create(struct path *path, struct dentry *dentry)
 	mnt_drop_write(path->mnt);
 	path_put(path);
 }
-EXPORT_SYMBOL(done_path_create);
+EXPORT_SYMBOL(end_creating_path);
 
-inline struct dentry *user_path_create(int dfd, const char __user *pathname,
-				struct path *path, unsigned int lookup_flags)
+inline struct dentry *start_creating_user_path(
+	int dfd, const char __user *pathname,
+	struct path *path, unsigned int lookup_flags)
 {
 	struct filename *filename = getname(pathname);
 	struct dentry *res = filename_create(dfd, filename, path, lookup_flags);
@@ -4253,7 +4268,7 @@ inline struct dentry *user_path_create(int dfd, const char __user *pathname,
 	putname(filename);
 	return res;
 }
-EXPORT_SYMBOL(user_path_create);
+EXPORT_SYMBOL(start_creating_user_path);
 
 /**
  * vfs_mknod - create device node or file
@@ -4361,7 +4376,7 @@ static int do_mknodat(int dfd, struct filename *name, umode_t mode,
 			break;
 	}
 out2:
-	done_path_create(&path, dentry);
+	end_creating_path(&path, dentry);
 	if (retry_estale(error, lookup_flags)) {
 		lookup_flags |= LOOKUP_REVAL;
 		goto retry;
@@ -4465,7 +4480,7 @@ int do_mkdirat(int dfd, struct filename *name, umode_t mode)
 		if (IS_ERR(dentry))
 			error = PTR_ERR(dentry);
 	}
-	done_path_create(&path, dentry);
+	end_creating_path(&path, dentry);
 	if (retry_estale(error, lookup_flags)) {
 		lookup_flags |= LOOKUP_REVAL;
 		goto retry;
@@ -4819,7 +4834,7 @@ int do_symlinkat(struct filename *from, int newdfd, struct filename *to)
 	if (!error)
 		error = vfs_symlink(mnt_idmap(path.mnt), path.dentry->d_inode,
 				    dentry, from->name);
-	done_path_create(&path, dentry);
+	end_creating_path(&path, dentry);
 	if (retry_estale(error, lookup_flags)) {
 		lookup_flags |= LOOKUP_REVAL;
 		goto retry;
@@ -4988,7 +5003,7 @@ int do_linkat(int olddfd, struct filename *old, int newdfd,
 	error = vfs_link(old_path.dentry, idmap, new_path.dentry->d_inode,
 			 new_dentry, &delegated_inode);
 out_dput:
-	done_path_create(&new_path, new_dentry);
+	end_creating_path(&new_path, new_dentry);
 	if (delegated_inode) {
 		error = break_deleg_wait(&delegated_inode);
 		if (!error) {
diff --git a/fs/ocfs2/refcounttree.c b/fs/ocfs2/refcounttree.c
index 8f732742b26e..267b50e8e42e 100644
--- a/fs/ocfs2/refcounttree.c
+++ b/fs/ocfs2/refcounttree.c
@@ -4418,7 +4418,7 @@ int ocfs2_reflink_ioctl(struct inode *inode,
 		return error;
 	}
 
-	new_dentry = user_path_create(AT_FDCWD, newname, &new_path, 0);
+	new_dentry = start_creating_user_path(AT_FDCWD, newname, &new_path, 0);
 	error = PTR_ERR(new_dentry);
 	if (IS_ERR(new_dentry)) {
 		mlog_errno(error);
@@ -4435,7 +4435,7 @@ int ocfs2_reflink_ioctl(struct inode *inode,
 				  d_inode(new_path.dentry),
 				  new_dentry, preserve);
 out_dput:
-	done_path_create(&new_path, new_dentry);
+	end_creating_path(&new_path, new_dentry);
 out:
 	path_put(&old_path);
 
diff --git a/fs/smb/server/vfs.c b/fs/smb/server/vfs.c
index 07739055ac9f..1cfa688904b2 100644
--- a/fs/smb/server/vfs.c
+++ b/fs/smb/server/vfs.c
@@ -196,7 +196,7 @@ int ksmbd_vfs_create(struct ksmbd_work *work, const char *name, umode_t mode)
 		pr_err("File(%s): creation failed (err:%d)\n", name, err);
 	}
 
-	done_path_create(&path, dentry);
+	end_creating_path(&path, dentry);
 	return err;
 }
 
@@ -237,7 +237,7 @@ int ksmbd_vfs_mkdir(struct ksmbd_work *work, const char *name, umode_t mode)
 	if (!err && dentry != d)
 		ksmbd_vfs_inherit_owner(work, d_inode(path.dentry), d_inode(dentry));
 
-	done_path_create(&path, dentry);
+	end_creating_path(&path, dentry);
 	if (err)
 		pr_err("mkdir(%s): creation failed (err:%d)\n", name, err);
 	return err;
@@ -669,7 +669,7 @@ int ksmbd_vfs_link(struct ksmbd_work *work, const char *oldname,
 		ksmbd_debug(VFS, "vfs_link failed err %d\n", err);
 
 out3:
-	done_path_create(&newpath, dentry);
+	end_creating_path(&newpath, dentry);
 out2:
 	path_put(&oldpath);
 out1:
@@ -1325,7 +1325,7 @@ struct dentry *ksmbd_vfs_kern_path_create(struct ksmbd_work *work,
 	if (!abs_name)
 		return ERR_PTR(-ENOMEM);
 
-	dent = kern_path_create(AT_FDCWD, abs_name, path, flags);
+	dent = start_creating_path(AT_FDCWD, abs_name, path, flags);
 	kfree(abs_name);
 	return dent;
 }
diff --git a/include/linux/namei.h b/include/linux/namei.h
index 1d5038c21c20..a7800ef04e76 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -59,11 +59,15 @@ struct dentry *lookup_one_qstr_excl(const struct qstr *name,
 extern int kern_path(const char *, unsigned, struct path *);
 struct dentry *kern_path_parent(const char *name, struct path *parent);
 
-extern struct dentry *kern_path_create(int, const char *, struct path *, unsigned int);
-extern struct dentry *user_path_create(int, const char __user *, struct path *, unsigned int);
-extern void done_path_create(struct path *, struct dentry *);
-extern struct dentry *kern_path_locked(const char *, struct path *);
-extern struct dentry *user_path_locked_at(int , const char __user *, struct path *);
+extern struct dentry *start_creating_path(int, const char *, struct path *, unsigned int);
+extern struct dentry *start_creating_user_path(int, const char __user *, struct path *, unsigned int);
+extern void end_creating_path(struct path *, struct dentry *);
+extern struct dentry *start_removing_path(const char *, struct path *);
+extern struct dentry *start_removing_user_path_at(int , const char __user *, struct path *);
+static inline void end_removing_path(struct path *path , struct dentry *dentry)
+{
+	end_creating_path(path, dentry);
+}
 int vfs_path_parent_lookup(struct filename *filename, unsigned int flags,
 			   struct path *parent, struct qstr *last, int *type,
 			   const struct path *root);
diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c
index 5c2e96b19392..fadf3817a9c5 100644
--- a/kernel/bpf/inode.c
+++ b/kernel/bpf/inode.c
@@ -442,7 +442,7 @@ static int bpf_obj_do_pin(int path_fd, const char __user *pathname, void *raw,
 	umode_t mode;
 	int ret;
 
-	dentry = user_path_create(path_fd, pathname, &path, 0);
+	dentry = start_creating_user_path(path_fd, pathname, &path, 0);
 	if (IS_ERR(dentry))
 		return PTR_ERR(dentry);
 
@@ -471,7 +471,7 @@ static int bpf_obj_do_pin(int path_fd, const char __user *pathname, void *raw,
 		ret = -EPERM;
 	}
 out:
-	done_path_create(&path, dentry);
+	end_creating_path(&path, dentry);
 	return ret;
 }
 
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 6d7c110814ff..768098dec231 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1387,7 +1387,7 @@ static int unix_bind_bsd(struct sock *sk, struct sockaddr_un *sunaddr,
 	 * Get the parent directory, calculate the hash for last
 	 * component.
 	 */
-	dentry = kern_path_create(AT_FDCWD, addr->name->sun_path, &parent, 0);
+	dentry = start_creating_path(AT_FDCWD, addr->name->sun_path, &parent, 0);
 	if (IS_ERR(dentry)) {
 		err = PTR_ERR(dentry);
 		goto out;
@@ -1417,7 +1417,7 @@ static int unix_bind_bsd(struct sock *sk, struct sockaddr_un *sunaddr,
 	unix_table_double_unlock(net, old_hash, new_hash);
 	unix_insert_bsd_socket(sk);
 	mutex_unlock(&u->bindlock);
-	done_path_create(&parent, dentry);
+	end_creating_path(&parent, dentry);
 	return 0;
 
 out_unlock:
@@ -1427,7 +1427,7 @@ static int unix_bind_bsd(struct sock *sk, struct sockaddr_un *sunaddr,
 	/* failed after successful mknod?  unlink what we'd created... */
 	vfs_unlink(idmap, d_inode(parent.dentry), dentry, NULL);
 out_path:
-	done_path_create(&parent, dentry);
+	end_creating_path(&parent, dentry);
 out:
 	unix_release_addr(addr);
 	return err == -EEXIST ? -EADDRINUSE : err;
-- 
2.50.0.107.gf914562f5916.dirty

[PATCH v3 6/6] debugfs: rename start_creating() to debugfs_start_creating()

[NeilBrown]

From: NeilBrown <neil@brown.name>

start_creating() is a generic name which I would like to use for a
function similar to simple_start_creating(), only not quite so simple.

debugfs is using this name which, though static, will cause complaints
if then name is given a different signature in a header file.

So rename it to debugfs_start_creating().

Signed-off-by: NeilBrown <neil@brown.name>
---
 fs/debugfs/inode.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index c12d649df6a5..661a99a7dfbe 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -362,7 +362,8 @@ struct dentry *debugfs_lookup(const char *name, struct dentry *parent)
 }
 EXPORT_SYMBOL_GPL(debugfs_lookup);
 
-static struct dentry *start_creating(const char *name, struct dentry *parent)
+static struct dentry *debugfs_start_creating(const char *name,
+					     struct dentry *parent)
 {
 	struct dentry *dentry;
 	int error;
@@ -428,7 +429,7 @@ static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
 	if (!(mode & S_IFMT))
 		mode |= S_IFREG;
 	BUG_ON(!S_ISREG(mode));
-	dentry = start_creating(name, parent);
+	dentry = debugfs_start_creating(name, parent);
 
 	if (IS_ERR(dentry))
 		return dentry;
@@ -577,7 +578,7 @@ EXPORT_SYMBOL_GPL(debugfs_create_file_size);
  */
 struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
 {
-	struct dentry *dentry = start_creating(name, parent);
+	struct dentry *dentry = debugfs_start_creating(name, parent);
 	struct inode *inode;
 
 	if (IS_ERR(dentry))
@@ -624,7 +625,7 @@ struct dentry *debugfs_create_automount(const char *name,
 					debugfs_automount_t f,
 					void *data)
 {
-	struct dentry *dentry = start_creating(name, parent);
+	struct dentry *dentry = debugfs_start_creating(name, parent);
 	struct inode *inode;
 
 	if (IS_ERR(dentry))
@@ -687,7 +688,7 @@ struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
 	if (!link)
 		return ERR_PTR(-ENOMEM);
 
-	dentry = start_creating(name, parent);
+	dentry = debugfs_start_creating(name, parent);
 	if (IS_ERR(dentry)) {
 		kfree(link);
 		return dentry;
-- 
2.50.0.107.gf914562f5916.dirty

Re: [PATCH v3 6/6] debugfs: rename start_creating() to debugfs_start_creating()

[Al Viro]

On Mon, Sep 15, 2025 at 12:13:46PM +1000, NeilBrown wrote:
> From: NeilBrown <neil@brown.name>
> 
> start_creating() is a generic name which I would like to use for a
> function similar to simple_start_creating(), only not quite so simple.
> 
> debugfs is using this name which, though static, will cause complaints
> if then name is given a different signature in a header file.
> 
> So rename it to debugfs_start_creating().

FWIW, there's one thing that might conflict with.  Take a look at this
in 3 of 4 callers of that thing:

        dentry = start_creating(name, parent);
 
        if (IS_ERR(dentry))
                return dentry;
 
        if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
                failed_creating(dentry);
                return ERR_PTR(-EPERM);
        }

Now, note that the very first thing start_creating() does is

        if (!(debugfs_allow & DEBUGFS_ALLOW_API))  
                return ERR_PTR(-EPERM);

and that debugfs_allow is assign-once variable - it's set only debugfs_kernel(),
called only via
early_param("debugfs", debugfs_kernel);

So that's dead code and had always been such.  All those checks had been added
at the same point - in a24c6f7bc923 "debugfs: Add access restriction option",
so at a guess the dead ones are rudiments from an earlier version of that patch
that hadn't been taken out by an accident - they should've been taken out and
shot on review, really.

They obviously need to go and that'll be textually close enough to the calls of
start_creating() to cause conflicts.

Re: [PATCH v3 6/6] debugfs: rename start_creating() to debugfs_start_creating()

[NeilBrown]

On Fri, 19 Sep 2025, Al Viro wrote:
> On Mon, Sep 15, 2025 at 12:13:46PM +1000, NeilBrown wrote:
> > From: NeilBrown <neil@brown.name>
> > 
> > start_creating() is a generic name which I would like to use for a
> > function similar to simple_start_creating(), only not quite so simple.
> > 
> > debugfs is using this name which, though static, will cause complaints
> > if then name is given a different signature in a header file.
> > 
> > So rename it to debugfs_start_creating().
> 
> FWIW, there's one thing that might conflict with.  Take a look at this
> in 3 of 4 callers of that thing:
> 
>         dentry = start_creating(name, parent);
>  
>         if (IS_ERR(dentry))
>                 return dentry;
>  
>         if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
>                 failed_creating(dentry);
>                 return ERR_PTR(-EPERM);
>         }
> 
> Now, note that the very first thing start_creating() does is
> 
>         if (!(debugfs_allow & DEBUGFS_ALLOW_API))  
>                 return ERR_PTR(-EPERM);
> 
> and that debugfs_allow is assign-once variable - it's set only debugfs_kernel(),
> called only via
> early_param("debugfs", debugfs_kernel);
> 
> So that's dead code and had always been such.  All those checks had been added
> at the same point - in a24c6f7bc923 "debugfs: Add access restriction option",
> so at a guess the dead ones are rudiments from an earlier version of that patch
> that hadn't been taken out by an accident - they should've been taken out and
> shot on review, really.
> 
> They obviously need to go and that'll be textually close enough to the calls of
> start_creating() to cause conflicts.
> 

I think your concerns are misplaced.
I just created two branches, one which renamed start_creating and one
which removed the redundant DEBUGFS_ALLOW_API checks, and then asked git
to merge them.
It said:

Auto-merging fs/debugfs/inode.c
Merge made by the 'ort' strategy.
 fs/debugfs/inode.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

It had no difficulty at all.

NeilBrown

Re: [PATCH v3 5/6] VFS: rename kern_path_locked() and related functions.

[kernel test robot]

Hello,

kernel test robot noticed "BUG:unable_to_handle_page_fault_for_address" on:

commit: 747e356babd8bdd569320c29916470345afd3cf7 ("[PATCH v3 5/6] VFS: rename kern_path_locked() and related functions.")
url: https://github.com/intel-lab-lkp/linux/commits/NeilBrown/VFS-ovl-add-lookup_one_positive_killable/20250915-101929
base: https://git.kernel.org/cgit/linux/kernel/git/vfs/vfs.git vfs.all
patch link: https://lore.kernel.org/all/20250915021504.2632889-6-neilb@ownmail.net/
patch subject: [PATCH v3 5/6] VFS: rename kern_path_locked() and related functions.

in testcase: boot

config: i386-randconfig-2006-20250825
compiler: gcc-14
test machine: qemu-system-i386 -enable-kvm -cpu SandyBridge -smp 2 -m 4G

(please refer to attached dmesg/kmsg for entire log/backtrace)


+---------------------------------------------+------------+------------+
|                                             | 1c87fa0646 | 747e356bab |
+---------------------------------------------+------------+------------+
| boot_successes                              | 24         | 0          |
| boot_failures                               | 0          | 24         |
| BUG:unable_to_handle_page_fault_for_address | 0          | 24         |
| Oops:Oops:#[##]                             | 0          | 24         |
| EIP:mnt_want_write                          | 0          | 24         |
| Kernel_panic-not_syncing:Fatal_exception    | 0          | 24         |
+---------------------------------------------+------------+------------+


If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <oliver.sang@intel.com>
| Closes: https://lore.kernel.org/oe-lkp/202509211121.ebd9f4b0-lkp@intel.com


[   12.277015][   T18] BUG: unable to handle page fault for address: fefeff02
[   12.278063][   T18] #PF: supervisor read access in kernel mode
[   12.278982][   T18] #PF: error_code(0x0000) - not-present page
[   12.279886][   T18] *pde = 00000000
[   12.280491][   T18] Oops: Oops: 0000 [#1]
[   12.281158][   T18] CPU: 0 UID: 0 PID: 18 Comm: kdevtmpfs Not tainted 6.17.0-rc3-00100-g747e356babd8 #1 PREEMPT(full)  97a7d9f1f9975edf00ea02f43ed800cec17522a0
[   12.283292][   T18] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[ 12.283887][ T18] EIP: mnt_want_write (include/linux/fs.h:1908 include/linux/fs.h:2044 fs/namespace.c:566) 
[ 12.283887][ T18] Code: 74 26 00 55 83 e8 30 89 e5 e8 b0 ff ff ff 5d c3 2e 8d b4 26 00 00 00 00 8d b6 00 00 00 00 3e 8d 74 26 00 55 89 e5 56 53 89 c3 <8b> 40 04 05 d8 01 00 00 e8 67 f5 ff ff 89 d8 e8 90 e6 ff ff 89 c6
All code
========
   0:	74 26                	je     0x28
   2:	00 55 83             	add    %dl,-0x7d(%rbp)
   5:	e8 30 89 e5 e8       	call   0xffffffffe8e5893a
   a:	b0 ff                	mov    $0xff,%al
   c:	ff                   	(bad)
   d:	ff 5d c3             	lcall  *-0x3d(%rbp)
  10:	2e 8d b4 26 00 00 00 	cs lea 0x0(%rsi,%riz,1),%esi
  17:	00 
  18:	8d b6 00 00 00 00    	lea    0x0(%rsi),%esi
  1e:	3e 8d 74 26 00       	ds lea 0x0(%rsi,%riz,1),%esi
  23:	55                   	push   %rbp
  24:	89 e5                	mov    %esp,%ebp
  26:	56                   	push   %rsi
  27:	53                   	push   %rbx
  28:	89 c3                	mov    %eax,%ebx
  2a:*	8b 40 04             	mov    0x4(%rax),%eax		<-- trapping instruction
  2d:	05 d8 01 00 00       	add    $0x1d8,%eax
  32:	e8 67 f5 ff ff       	call   0xfffffffffffff59e
  37:	89 d8                	mov    %ebx,%eax
  39:	e8 90 e6 ff ff       	call   0xffffffffffffe6ce
  3e:	89 c6                	mov    %eax,%esi

Code starting with the faulting instruction
===========================================
   0:	8b 40 04             	mov    0x4(%rax),%eax
   3:	05 d8 01 00 00       	add    $0x1d8,%eax
   8:	e8 67 f5 ff ff       	call   0xfffffffffffff574
   d:	89 d8                	mov    %ebx,%eax
   f:	e8 90 e6 ff ff       	call   0xffffffffffffe6a4
  14:	89 c6                	mov    %eax,%esi
[   12.283887][   T18] EAX: fefefefe EBX: fefefefe ECX: c5923640 EDX: c58b9e28
[   12.283887][   T18] ESI: c58b9f0c EDI: c54024e0 EBP: c58b9ea4 ESP: c58b9e9c
[   12.283887][   T18] DS: 007b ES: 007b FS: 0000 GS: 0000 SS: 0068 EFLAGS: 00010246
[   12.283887][   T18] CR0: 80050033 CR2: fefeff02 CR3: 04780000 CR4: 000406d0
[   12.283887][   T18] Call Trace:
[ 12.283887][ T18] __start_removing_path (include/linux/fs.h:1024 fs/namei.c:2784) 
[ 12.283887][ T18] start_removing_path (fs/namei.c:2842) 
[ 12.283887][ T18] devtmpfs_work_loop (drivers/base/devtmpfs.c:326 drivers/base/devtmpfs.c:387 drivers/base/devtmpfs.c:400) 
[ 12.283887][ T18] devtmpfsd (drivers/base/devtmpfs.c:444) 
[ 12.283887][ T18] kthread (kernel/kthread.c:465) 
[ 12.283887][ T18] ? vclkdev_alloc (drivers/base/devtmpfs.c:436) 
[ 12.283887][ T18] ? kthread_is_per_cpu (kernel/kthread.c:412) 
[ 12.283887][ T18] ret_from_fork (arch/x86/kernel/process.c:154) 
[ 12.283887][ T18] ? kthread_is_per_cpu (kernel/kthread.c:412) 
[ 12.283887][ T18] ret_from_fork_asm (arch/x86/entry/entry_32.S:737) 
[ 12.283887][ T18] entry_INT80_32 (arch/x86/entry/entry_32.S:945) 
[   12.283887][   T18] Modules linked in:
[   12.283887][   T18] CR2: 00000000fefeff02
[   12.283887][   T18] ---[ end trace 0000000000000000 ]---
[ 12.283887][ T18] EIP: mnt_want_write (include/linux/fs.h:1908 include/linux/fs.h:2044 fs/namespace.c:566) 
[ 12.283887][ T18] Code: 74 26 00 55 83 e8 30 89 e5 e8 b0 ff ff ff 5d c3 2e 8d b4 26 00 00 00 00 8d b6 00 00 00 00 3e 8d 74 26 00 55 89 e5 56 53 89 c3 <8b> 40 04 05 d8 01 00 00 e8 67 f5 ff ff 89 d8 e8 90 e6 ff ff 89 c6
All code
========
   0:	74 26                	je     0x28
   2:	00 55 83             	add    %dl,-0x7d(%rbp)
   5:	e8 30 89 e5 e8       	call   0xffffffffe8e5893a
   a:	b0 ff                	mov    $0xff,%al
   c:	ff                   	(bad)
   d:	ff 5d c3             	lcall  *-0x3d(%rbp)
  10:	2e 8d b4 26 00 00 00 	cs lea 0x0(%rsi,%riz,1),%esi
  17:	00 
  18:	8d b6 00 00 00 00    	lea    0x0(%rsi),%esi
  1e:	3e 8d 74 26 00       	ds lea 0x0(%rsi,%riz,1),%esi
  23:	55                   	push   %rbp
  24:	89 e5                	mov    %esp,%ebp
  26:	56                   	push   %rsi
  27:	53                   	push   %rbx
  28:	89 c3                	mov    %eax,%ebx
  2a:*	8b 40 04             	mov    0x4(%rax),%eax		<-- trapping instruction
  2d:	05 d8 01 00 00       	add    $0x1d8,%eax
  32:	e8 67 f5 ff ff       	call   0xfffffffffffff59e
  37:	89 d8                	mov    %ebx,%eax
  39:	e8 90 e6 ff ff       	call   0xffffffffffffe6ce
  3e:	89 c6                	mov    %eax,%esi

Code starting with the faulting instruction
===========================================
   0:	8b 40 04             	mov    0x4(%rax),%eax
   3:	05 d8 01 00 00       	add    $0x1d8,%eax
   8:	e8 67 f5 ff ff       	call   0xfffffffffffff574
   d:	89 d8                	mov    %ebx,%eax
   f:	e8 90 e6 ff ff       	call   0xffffffffffffe6a4
  14:	89 c6                	mov    %eax,%esi


The kernel config and materials to reproduce are available at:
https://download.01.org/0day-ci/archive/20250921/202509211121.ebd9f4b0-lkp@intel.com



-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH v3 5/6] VFS: rename kern_path_locked() and related functions.

[NeilBrown]

On Sun, 21 Sep 2025, kernel test robot wrote:
> 
> Hello,
> 
> kernel test robot noticed "BUG:unable_to_handle_page_fault_for_address" on:
> 
> commit: 747e356babd8bdd569320c29916470345afd3cf7 ("[PATCH v3 5/6] VFS: rename kern_path_locked() and related functions.")
> url: https://github.com/intel-lab-lkp/linux/commits/NeilBrown/VFS-ovl-add-lookup_one_positive_killable/20250915-101929
> base: https://git.kernel.org/cgit/linux/kernel/git/vfs/vfs.git vfs.all
> patch link: https://lore.kernel.org/all/20250915021504.2632889-6-neilb@ownmail.net/
> patch subject: [PATCH v3 5/6] VFS: rename kern_path_locked() and related functions.

This incremental fix should be sufficient.

Thanks,
NeilBrown


diff --git a/fs/namei.c b/fs/namei.c
index 5ceb971632fe..92973a7a8091 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2772,7 +2772,7 @@ static struct dentry *__start_removing_path(int dfd, struct filename *name,
 	if (unlikely(type != LAST_NORM))
 		return ERR_PTR(-EINVAL);
 	/* don't fail immediately if it's r/o, at least try to report other errors */
-	error = mnt_want_write(path->mnt);
+	error = mnt_want_write(parent_path.mnt);
 	inode_lock_nested(parent_path.dentry->d_inode, I_MUTEX_PARENT);
 	d = lookup_one_qstr_excl(&last, parent_path.dentry, 0);
 	if (IS_ERR(d))
@@ -2789,7 +2789,7 @@ static struct dentry *__start_removing_path(int dfd, struct filename *name,
 unlock:
 	inode_unlock(parent_path.dentry->d_inode);
 	if (!error)
-		mnt_drop_write(path->mnt);
+		mnt_drop_write(parent_path.mnt);
 	return d;
 }