fsnotify: implement ordering between notifiers

fanotify needs to be able to specify that some groups get events before
others.  They use this idea to make sure that a hierarchical storage
manager gets access to files before programs which actually use them.  This
is purely infrastructure.  Everything will have a priority of 0, but the
infrastructure will exist for it to be non-zero.

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

1 files changed, 8 insertions, 0 deletions

diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index e40190d16878..825329534162 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -129,6 +129,14 @@ struct fsnotify_group {
         wait_queue_head_t notification_waitq;   /* read() on the notification file blocks on this waitq */
         unsigned int q_len;                     /* events on the queue */
         unsigned int max_events;                /* maximum events allowed on the list */
+        /*
+         * Valid fsnotify group priorities.  Events are send in order from highest
+         * priority to lowest priority.  We default to the lowest priority.
+         */
+        #define FS_PRIO_0       0 /* normal notifiers, no permissions */
+        #define FS_PRIO_1       1 /* fanotify content based access control */
+        #define FS_PRIO_2       2 /* fanotify pre-content access */
+        unsigned int priority;
 
         /* stores all fastpath marks assoc with this group so they can be cleaned on unregister */
         spinlock_t mark_lock;           /* protect marks_list */