fsnotify: ignored_mask - excluding notification

The ignored_mask is a new mask which is part of fsnotify marks.  A group's
should_send_event() function can use the ignored mask to determine that
certain events are not of interest.  In particular if a group registers a
mask including FS_OPEN on a vfsmount they could add FS_OPEN to the
ignored_mask for individual inodes and not send open events for those
inodes.
Signed-off-by: Eric Paris <eparis@redhat.com>

fs/notify/mark.c

@@ -190,6 +190,12 @@ void fsnotify_set_mark_mask_locked(struct fsnotify_mark *mark, __u32 mask)
 		fsnotify_set_inode_mark_mask_locked(mark, mask);
 }
 
+void fsnotify_set_mark_ignored_mask_locked(struct fsnotify_mark *mark, __u32 mask)
+{
+	assert_spin_locked(&mark->lock);
+
+	mark->ignored_mask = mask;
+}
 
 /*
  * Attach an initialized mark to a given group and fs object.

include/linux/fsnotify_backend.h

@@ -266,6 +266,7 @@ struct fsnotify_mark {
 		struct fsnotify_inode_mark i;
 		struct fsnotify_vfsmount_mark m;
 	};
+	__u32 ignored_mask;		/* events types to ignore */
 	struct list_head free_g_list;	/* tmp list used when freeing this mark */
 #define FSNOTIFY_MARK_FLAG_INODE		0x01
 #define FSNOTIFY_MARK_FLAG_VFSMOUNT		0x02
@@ -373,6 +374,8 @@ extern struct fsnotify_mark *fsnotify_find_inode_mark(struct fsnotify_group *gro
 extern struct fsnotify_mark *fsnotify_find_vfsmount_mark(struct fsnotify_group *group, struct vfsmount *mnt);
 /* copy the values from old into new */
 extern void fsnotify_duplicate_mark(struct fsnotify_mark *new, struct fsnotify_mark *old);
+/* set the ignored_mask of a mark */
+extern void fsnotify_set_mark_ignored_mask_locked(struct fsnotify_mark *mark, __u32 mask);
 /* set the mask of a mark (might pin the object into memory */
 extern void fsnotify_set_mark_mask_locked(struct fsnotify_mark *mark, __u32 mask);
 /* attach the mark to both the group and the inode */