[PATCH 5.1 069/122] fsnotify: fix unlink performance regression

Greg Kroah-Hartman
2019-05-23T19:33:51Z

From: Amir Goldstein <amir73il@gmail.com>

commit 4d8e7055a4058ee191296699803c5090e14f0dff upstream.

__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: 5f02a8776384 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/notify/fsnotify.c | 41 +++++++++++++++++++++++++++++++++++++++
include/linux/fsnotify.h | 33 -------------------------------
include/linux/fsnotify_backend.h | 4 +++
3 files changed, 45 insertions(+), 33 deletions(-)

--- a/fs/notify/fsnotify.c
+++ b/fs/notify/fsnotify.c
@@ -108,6 +108,47 @@ void fsnotify_sb_delete(struct super_blo
}

/*
+ * 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
* on a child we run all of our children and set a dentry flag saying that the
--- a/include/linux/fsnotify.h
+++ b/include/linux/fsnotify.h
@@ -152,39 +152,6 @@ static inline void fsnotify_vfsmount_del
}

/*
- * 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
*/
static inline void fsnotify_inoderemove(struct inode *inode)
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -355,6 +355,7 @@ extern int __fsnotify_parent(const struc
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_d
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)
{}