inotify: use GFP_NOFS under potential memory pressure

inotify can have a watchs removed under filesystem reclaim.

=================================
[ INFO: inconsistent lock state ]
2.6.31-rc2 #16
---------------------------------
inconsistent {IN-RECLAIM_FS-W} -> {RECLAIM_FS-ON-W} usage.
khubd/217 [HC0[0]:SC0[0]:HE1:SE1] takes:
 (iprune_mutex){+.+.?.}, at: [<c10ba899>] invalidate_inodes+0x20/0xe3
{IN-RECLAIM_FS-W} state was registered at:
  [<c10536ab>] __lock_acquire+0x2c9/0xac4
  [<c1053f45>] lock_acquire+0x9f/0xc2
  [<c1308872>] __mutex_lock_common+0x2d/0x323
  [<c1308c00>] mutex_lock_nested+0x2e/0x36
  [<c10ba6ff>] shrink_icache_memory+0x38/0x1b2
  [<c108bfb6>] shrink_slab+0xe2/0x13c
  [<c108c3e1>] kswapd+0x3d1/0x55d
  [<c10449b5>] kthread+0x66/0x6b
  [<c1003fdf>] kernel_thread_helper+0x7/0x10
  [<ffffffff>] 0xffffffff

Two things are needed to fix this.  First we need a method to tell
fsnotify_create_event() to use GFP_NOFS and second we need to stop using
one global IN_IGNORED event and allocate them one at a time.  This solves
current issues with multiple IN_IGNORED on a queue having tail drop
problems and simplifies the allocations since we don't have to worry about
two tasks opperating on the IGNORED event concurrently.

Signed-off-by: Eric Paris <eparis@redhat.com>

1 files changed, 5 insertions, 4 deletions

diff --git a/fs/notify/notification.c b/fs/notify/notification.c
index 2b20feaf263a..521368574e97 100644
--- a/fs/notify/notification.c
+++ b/fs/notify/notification.c
@@ -153,7 +153,7 @@ static bool event_compare(struct fsnotify_event *old, struct fsnotify_event *new
 				return true;
 			break;
 		case (FSNOTIFY_EVENT_NONE):
-			return true;
+			return false;
 		};
 	}
 	return false;
@@ -345,18 +345,19 @@ static void initialize_event(struct fsnotify_event *event)
  * @name the filename, if available
  */
 struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask, void *data,
-					     int data_type, const char *name, u32 cookie)
+					     int data_type, const char *name, u32 cookie,
+					     gfp_t gfp)
 {
 	struct fsnotify_event *event;
 
-	event = kmem_cache_alloc(fsnotify_event_cachep, GFP_KERNEL);
+	event = kmem_cache_alloc(fsnotify_event_cachep, gfp);
 	if (!event)
 		return NULL;
 
 	initialize_event(event);
 
 	if (name) {
-		event->file_name = kstrdup(name, GFP_KERNEL);
+		event->file_name = kstrdup(name, gfp);
 		if (!event->file_name) {
 			kmem_cache_free(fsnotify_event_cachep, event);
 			return NULL;