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authorJan Kara <jack@suse.com>2015-09-04 15:43:12 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-09-04 16:54:41 -0700
commit4712e722f91457e60723b9cef6265a74290efba9 (patch)
treeb6b4bf48018d23c180cb7407ea1ff58402664e5c /fs/notify/mark.c
parent925d1132a03e33cb8f29a0057300d023b4f1be23 (diff)
fsnotify: get rid of fsnotify_destroy_mark_locked()
fsnotify_destroy_mark_locked() is subtle to use because it temporarily releases group->mark_mutex. To avoid future problems with this function, split it into two. fsnotify_detach_mark() is the part that needs group->mark_mutex and fsnotify_free_mark() is the part that must be called outside of group->mark_mutex. This way it's much clearer what's going on and we also avoid some pointless acquisitions of group->mark_mutex. Signed-off-by: Jan Kara <jack@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/notify/mark.c')
-rw-r--r--fs/notify/mark.c73
1 files changed, 40 insertions, 33 deletions
diff --git a/fs/notify/mark.c b/fs/notify/mark.c
index 3b2d1ba41e7b..fc0df4442f7b 100644
--- a/fs/notify/mark.c
+++ b/fs/notify/mark.c
@@ -122,26 +122,27 @@ u32 fsnotify_recalc_mask(struct hlist_head *head)
}
/*
- * Any time a mark is getting freed we end up here.
- * The caller had better be holding a reference to this mark so we don't actually
- * do the final put under the mark->lock
+ * Remove mark from inode / vfsmount list, group list, drop inode reference
+ * if we got one.
+ *
+ * Must be called with group->mark_mutex held.
*/
-void fsnotify_destroy_mark_locked(struct fsnotify_mark *mark,
- struct fsnotify_group *group)
+void fsnotify_detach_mark(struct fsnotify_mark *mark)
{
struct inode *inode = NULL;
+ struct fsnotify_group *group = mark->group;
BUG_ON(!mutex_is_locked(&group->mark_mutex));
spin_lock(&mark->lock);
/* something else already called this function on this mark */
- if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) {
+ if (!(mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)) {
spin_unlock(&mark->lock);
return;
}
- mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;
+ mark->flags &= ~FSNOTIFY_MARK_FLAG_ATTACHED;
if (mark->flags & FSNOTIFY_MARK_FLAG_INODE) {
inode = mark->inode;
@@ -150,6 +151,12 @@ void fsnotify_destroy_mark_locked(struct fsnotify_mark *mark,
fsnotify_destroy_vfsmount_mark(mark);
else
BUG();
+ /*
+ * Note that we didn't update flags telling whether inode cares about
+ * what's happening with children. We update these flags from
+ * __fsnotify_parent() lazily when next event happens on one of our
+ * children.
+ */
list_del_init(&mark->g_list);
@@ -157,18 +164,32 @@ void fsnotify_destroy_mark_locked(struct fsnotify_mark *mark,
if (inode && (mark->flags & FSNOTIFY_MARK_FLAG_OBJECT_PINNED))
iput(inode);
- /* release lock temporarily */
- mutex_unlock(&group->mark_mutex);
+
+ atomic_dec(&group->num_marks);
+}
+
+/*
+ * Free fsnotify mark. The freeing is actually happening from a kthread which
+ * first waits for srcu period end. Caller must have a reference to the mark
+ * or be protected by fsnotify_mark_srcu.
+ */
+void fsnotify_free_mark(struct fsnotify_mark *mark)
+{
+ struct fsnotify_group *group = mark->group;
+
+ spin_lock(&mark->lock);
+ /* something else already called this function on this mark */
+ if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) {
+ spin_unlock(&mark->lock);
+ return;
+ }
+ mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;
+ spin_unlock(&mark->lock);
spin_lock(&destroy_lock);
list_add(&mark->g_list, &destroy_list);
spin_unlock(&destroy_lock);
wake_up(&destroy_waitq);
- /*
- * We don't necessarily have a ref on mark from caller so the above destroy
- * may have actually freed it, unless this group provides a 'freeing_mark'
- * function which must be holding a reference.
- */
/*
* Some groups like to know that marks are being freed. This is a
@@ -177,30 +198,15 @@ void fsnotify_destroy_mark_locked(struct fsnotify_mark *mark,
*/
if (group->ops->freeing_mark)
group->ops->freeing_mark(mark, group);
-
- /*
- * __fsnotify_update_child_dentry_flags(inode);
- *
- * I really want to call that, but we can't, we have no idea if the inode
- * still exists the second we drop the mark->lock.
- *
- * The next time an event arrive to this inode from one of it's children
- * __fsnotify_parent will see that the inode doesn't care about it's
- * children and will update all of these flags then. So really this
- * is just a lazy update (and could be a perf win...)
- */
-
- atomic_dec(&group->num_marks);
-
- mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING);
}
void fsnotify_destroy_mark(struct fsnotify_mark *mark,
struct fsnotify_group *group)
{
mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING);
- fsnotify_destroy_mark_locked(mark, group);
+ fsnotify_detach_mark(mark);
mutex_unlock(&group->mark_mutex);
+ fsnotify_free_mark(mark);
}
void fsnotify_destroy_marks(struct hlist_head *head, spinlock_t *lock)
@@ -342,7 +348,7 @@ int fsnotify_add_mark_locked(struct fsnotify_mark *mark,
* inode->i_lock
*/
spin_lock(&mark->lock);
- mark->flags |= FSNOTIFY_MARK_FLAG_ALIVE;
+ mark->flags |= FSNOTIFY_MARK_FLAG_ALIVE | FSNOTIFY_MARK_FLAG_ATTACHED;
fsnotify_get_group(group);
mark->group = group;
@@ -448,8 +454,9 @@ void fsnotify_clear_marks_by_group_flags(struct fsnotify_group *group,
}
mark = list_first_entry(&to_free, struct fsnotify_mark, g_list);
fsnotify_get_mark(mark);
- fsnotify_destroy_mark_locked(mark, group);
+ fsnotify_detach_mark(mark);
mutex_unlock(&group->mark_mutex);
+ fsnotify_free_mark(mark);
fsnotify_put_mark(mark);
}
}