dnotify: replace dnotify_mark_mutex with mark mutex of dnotify_group

There is no need to use a special mutex to protect against the
fcntl/close race (see dnotify.c for a description of this race).
Instead the dnotify_groups mark mutex can be used.

Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Cc: Eric Paris <eparis@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 13 insertions, 12 deletions

diff --git a/fs/notify/dnotify/dnotify.c b/fs/notify/dnotify/dnotify.c
index 2bfe6dc413a0..1fedd5f7ccc4 100644
--- a/fs/notify/dnotify/dnotify.c
+++ b/fs/notify/dnotify/dnotify.c
@@ -31,7 +31,6 @@ int dir_notify_enable __read_mostly = 1;
 static struct kmem_cache *dnotify_struct_cache __read_mostly;
 static struct kmem_cache *dnotify_mark_cache __read_mostly;
 static struct fsnotify_group *dnotify_group __read_mostly;
-static DEFINE_MUTEX(dnotify_mark_mutex);
 
 /*
  * dnotify will attach one of these to each inode (i_fsnotify_marks) which
@@ -183,7 +182,7 @@ void dnotify_flush(struct file *filp, fl_owner_t id)
                 return;
         dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark);
 
-        mutex_lock(&dnotify_mark_mutex);
+        mutex_lock(&dnotify_group->mark_mutex);
 
         spin_lock(&fsn_mark->lock);
         prev = &dn_mark->dn;
@@ -199,11 +198,12 @@ void dnotify_flush(struct file *filp, fl_owner_t id)
 
         spin_unlock(&fsn_mark->lock);
 
-        /* nothing else could have found us thanks to the dnotify_mark_mutex */
+        /* nothing else could have found us thanks to the dnotify_groups
+           mark_mutex */
         if (dn_mark->dn == NULL)
-                fsnotify_destroy_mark(fsn_mark, dnotify_group);
+                fsnotify_destroy_mark_locked(fsn_mark, dnotify_group);
 
-        mutex_unlock(&dnotify_mark_mutex);
+        mutex_unlock(&dnotify_group->mark_mutex);
 
         fsnotify_put_mark(fsn_mark);
 }
@@ -326,7 +326,7 @@ int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg)
         new_dn_mark->dn = NULL;
 
         /* this is needed to prevent the fcntl/close race described below */
-        mutex_lock(&dnotify_mark_mutex);
+        mutex_lock(&dnotify_group->mark_mutex);
 
         /* add the new_fsn_mark or find an old one. */
         fsn_mark = fsnotify_find_inode_mark(dnotify_group, inode);
@@ -334,7 +334,8 @@ int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg)
                 dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark);
                 spin_lock(&fsn_mark->lock);
         } else {
-                fsnotify_add_mark(new_fsn_mark, dnotify_group, inode, NULL, 0);
+                fsnotify_add_mark_locked(new_fsn_mark, dnotify_group, inode,
+                                         NULL, 0);
                 spin_lock(&new_fsn_mark->lock);
                 fsn_mark = new_fsn_mark;
                 dn_mark = new_dn_mark;
@@ -348,9 +349,9 @@ int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg)
 
         /* if (f != filp) means that we lost a race and another task/thread
          * actually closed the fd we are still playing with before we grabbed
-         * the dnotify_mark_mutex and fsn_mark->lock.  Since closing the fd is the
-         * only time we clean up the marks we need to get our mark off
-         * the list. */
+         * the dnotify_groups mark_mutex and fsn_mark->lock.  Since closing the
+         * fd is the only time we clean up the marks we need to get our mark
+         * off the list. */
         if (f != filp) {
                 /* if we added ourselves, shoot ourselves, it's possible that
                  * the flush actually did shoot this fsn_mark.  That's fine too
@@ -385,9 +386,9 @@ out:
         spin_unlock(&fsn_mark->lock);
 
         if (destroy)
-                fsnotify_destroy_mark(fsn_mark, dnotify_group);
+                fsnotify_destroy_mark_locked(fsn_mark, dnotify_group);
 
-        mutex_unlock(&dnotify_mark_mutex);
+        mutex_unlock(&dnotify_group->mark_mutex);
         fsnotify_put_mark(fsn_mark);
 out_err:
         if (new_fsn_mark)