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Commit 4d8e7055 authored by Amir Goldstein's avatar Amir Goldstein Committed by Jan Kara
Browse files

fsnotify: fix unlink performance regression 



__fsnotify_parent() has an optimization in place to avoid unneeded
take_dentry_name_snapshot().  When fsnotify_nameremove() was changed
not to call __fsnotify_parent(), we left out the optimization.
Kernel test robot reported a 5% performance regression in concurrent
unlink() workload.

Reported-by: default avatarkernel test robot <rong.a.chen@intel.com>
Link: https://lore.kernel.org/lkml/20190505062153.GG29809@shao2-debian/
Link: https://lore.kernel.org/linux-fsdevel/20190104090357.GD22409@quack2.suse.cz/


Fixes: 5f02a877 ("fsnotify: annotate directory entry modification events")
CC: stable@vger.kernel.org
Signed-off-by: default avatarAmir Goldstein <amir73il@gmail.com>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
parent 11a6f8e2

fs/notify/fsnotify.c

+41 −0
Original line number Diff line number Diff line
@@ -107,6 +107,47 @@ void fsnotify_sb_delete(struct super_block *sb) 
	fsnotify_clear_marks_by_sb(sb);

}



/*

 * fsnotify_nameremove - a filename was removed from a directory

 *

 * This is mostly called under parent vfs inode lock so name and

 * dentry->d_parent should be stable. However there are some corner cases where

 * inode lock is not held. So to be on the safe side and be reselient to future

 * callers and out of tree users of d_delete(), we do not assume that d_parent

 * and d_name are stable and we use dget_parent() and

 * take_dentry_name_snapshot() to grab stable references.

 */

void fsnotify_nameremove(struct dentry *dentry, int isdir)

{

	struct dentry *parent;

	struct name_snapshot name;

	__u32 mask = FS_DELETE;



	/* d_delete() of pseudo inode? (e.g. __ns_get_path() playing tricks) */

	if (IS_ROOT(dentry))

		return;



	if (isdir)

		mask |= FS_ISDIR;



	parent = dget_parent(dentry);

	/* Avoid unneeded take_dentry_name_snapshot() */

	if (!(d_inode(parent)->i_fsnotify_mask & FS_DELETE) &&

	    !(dentry->d_sb->s_fsnotify_mask & FS_DELETE))

		goto out_dput;



	take_dentry_name_snapshot(&name, dentry);



	fsnotify(d_inode(parent), mask, d_inode(dentry), FSNOTIFY_EVENT_INODE,

		 name.name, 0);



	release_dentry_name_snapshot(&name);



out_dput:

	dput(parent);

}

EXPORT_SYMBOL(fsnotify_nameremove);



/*

 * Given an inode, first check if we care what happens to our children.  Inotify

 * and dnotify both tell their parents about events.  If we care about any event

include/linux/fsnotify.h

+0 −33
Original line number Diff line number Diff line
@@ -151,39 +151,6 @@ static inline void fsnotify_vfsmount_delete(struct vfsmount *mnt) 
	__fsnotify_vfsmount_delete(mnt);

}



/*

 * fsnotify_nameremove - a filename was removed from a directory

 *

 * This is mostly called under parent vfs inode lock so name and

 * dentry->d_parent should be stable. However there are some corner cases where

 * inode lock is not held. So to be on the safe side and be reselient to future

 * callers and out of tree users of d_delete(), we do not assume that d_parent

 * and d_name are stable and we use dget_parent() and

 * take_dentry_name_snapshot() to grab stable references.

 */

static inline void fsnotify_nameremove(struct dentry *dentry, int isdir)

{

	struct dentry *parent;

	struct name_snapshot name;

	__u32 mask = FS_DELETE;



	/* d_delete() of pseudo inode? (e.g. __ns_get_path() playing tricks) */

	if (IS_ROOT(dentry))

		return;



	if (isdir)

		mask |= FS_ISDIR;



	parent = dget_parent(dentry);

	take_dentry_name_snapshot(&name, dentry);



	fsnotify(d_inode(parent), mask, d_inode(dentry), FSNOTIFY_EVENT_INODE,

		 name.name, 0);



	release_dentry_name_snapshot(&name);

	dput(parent);

}



/*

 * fsnotify_inoderemove - an inode is going away

 */

include/linux/fsnotify_backend.h

+4 −0
Original line number Diff line number Diff line
@@ -355,6 +355,7 @@ extern int __fsnotify_parent(const struct path *path, struct dentry *dentry, __u 
extern void __fsnotify_inode_delete(struct inode *inode);

extern void __fsnotify_vfsmount_delete(struct vfsmount *mnt);

extern void fsnotify_sb_delete(struct super_block *sb);

extern void fsnotify_nameremove(struct dentry *dentry, int isdir);

extern u32 fsnotify_get_cookie(void);



static inline int fsnotify_inode_watches_children(struct inode *inode)
@@ -524,6 +525,9 @@ static inline void __fsnotify_vfsmount_delete(struct vfsmount *mnt) 
static inline void fsnotify_sb_delete(struct super_block *sb)

{}



static inline void fsnotify_nameremove(struct dentry *dentry, int isdir)

{}



static inline void fsnotify_update_flags(struct dentry *dentry)

{}