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Code Issues Releases Wiki Activity

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: kernel 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: 5f02a87763 ("fsnotify: annotate directory entry modification events")
CC: stable@vger.kernel.org
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
This commit is contained in:
Amir Goldstein 2019-05-05 12:15:49 +03:00 committed by Jan Kara
parent 11a6f8e2db
commit 4d8e7055a4
3 changed files with 45 additions and 33 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

41
fs/notify/fsnotify.c
View File

@ -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

33
include/linux/fsnotify.h
View File

@ -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
*/

4
include/linux/fsnotify_backend.h
View File

@ -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)
{}