fsnotify: remove group_num altogether

The original fsnotify interface has a group-num which was intended to be
able to find a group after it was added.  I no longer think this is a
necessary thing to do and so we remove the group_num.
Signed-off-by: NEric Paris <eparis@redhat.com>

fs/notify/dnotify/dnotify.c

@@ -433,8 +433,7 @@ static int __init dnotify_init(void)
 	dnotify_struct_cache = KMEM_CACHE(dnotify_struct, SLAB_PANIC);
 	dnotify_mark_entry_cache = KMEM_CACHE(dnotify_mark_entry, SLAB_PANIC);
 
-	dnotify_group = fsnotify_obtain_group(DNOTIFY_GROUP_NUM,
-					      0, &dnotify_fsnotify_ops);
+	dnotify_group = fsnotify_obtain_group(0, &dnotify_fsnotify_ops);
 	if (IS_ERR(dnotify_group))
 		panic("unable to allocate fsnotify group for dnotify\n");
 	return 0;

fs/notify/group.c

@@ -77,15 +77,6 @@ void fsnotify_recalc_group_mask(struct fsnotify_group *group)
 		fsnotify_recalc_global_mask();
 }
 
-/*
- * Take a reference to a group so things found under the fsnotify_grp_mutex
- * can't get freed under us
- */
-static void fsnotify_get_group(struct fsnotify_group *group)
-{
-	atomic_inc(&group->refcnt);
-}
-
 /*
  * Final freeing of a group
  */
@@ -170,41 +161,15 @@ void fsnotify_put_group(struct fsnotify_group *group)
 	fsnotify_destroy_group(group);
 }
 
-/*
- * Simply run the fsnotify_groups list and find a group which matches
- * the given parameters.  If a group is found we take a reference to that
- * group.
- */
-static struct fsnotify_group *fsnotify_find_group(unsigned int group_num, __u32 mask,
-						  const struct fsnotify_ops *ops)
-{
-	struct fsnotify_group *group_iter;
-	struct fsnotify_group *group = NULL;
-
-	BUG_ON(!mutex_is_locked(&fsnotify_grp_mutex));
-
-	list_for_each_entry_rcu(group_iter, &fsnotify_groups, group_list) {
-		if (group_iter->group_num == group_num) {
-			if ((group_iter->mask == mask) &&
-			    (group_iter->ops == ops)) {
-				fsnotify_get_group(group_iter);
-				group = group_iter;
-			} else
-				group = ERR_PTR(-EEXIST);
-		}
-	}
-	return group;
-}
-
 /*
  * Either finds an existing group which matches the group_num, mask, and ops or
  * creates a new group and adds it to the global group list.  In either case we
  * take a reference for the group returned.
  */
-struct fsnotify_group *fsnotify_obtain_group(unsigned int group_num, __u32 mask,
+struct fsnotify_group *fsnotify_obtain_group(__u32 mask,
 					     const struct fsnotify_ops *ops)
 {
-	struct fsnotify_group *group, *tgroup;
+	struct fsnotify_group *group;
 
 	/* very low use, simpler locking if we just always alloc */
 	group = kzalloc(sizeof(struct fsnotify_group), GFP_KERNEL);
@@ -214,7 +179,6 @@ struct fsnotify_group *fsnotify_obtain_group(unsigned int group_num, __u32 mask,
 	atomic_set(&group->refcnt, 1);
 
 	group->on_group_list = 0;
-	group->group_num = group_num;
 	group->mask = mask;
 
 	mutex_init(&group->notification_mutex);
@@ -230,14 +194,6 @@ struct fsnotify_group *fsnotify_obtain_group(unsigned int group_num, __u32 mask,
 	group->ops = ops;
 
 	mutex_lock(&fsnotify_grp_mutex);
-	tgroup = fsnotify_find_group(group_num, mask, ops);
-	if (tgroup) {
-		/* group already exists */
-		mutex_unlock(&fsnotify_grp_mutex);
-		/* destroy the new one we made */
-		fsnotify_put_group(group);
-		return tgroup;
-	}
 
 	/* group not found, add a new one */
 	list_add_rcu(&group->group_list, &fsnotify_groups);

fs/notify/inotify/inotify_user.c

@@ -51,12 +51,6 @@ int inotify_max_user_watches __read_mostly;
 static struct kmem_cache *inotify_inode_mark_cachep __read_mostly;
 struct kmem_cache *event_priv_cachep __read_mostly;
 
-/*
- * When inotify registers a new group it increments this and uses that
- * value as an offset to set the fsnotify group "name" and priority.
- */
-static atomic_t inotify_grp_num;
-
 #ifdef CONFIG_SYSCTL
 
 #include <linux/sysctl.h>
@@ -700,11 +694,8 @@ static int inotify_update_watch(struct fsnotify_group *group, struct inode *inod
 static struct fsnotify_group *inotify_new_group(struct user_struct *user, unsigned int max_events)
 {
 	struct fsnotify_group *group;
-	unsigned int grp_num;
 
-	/* fsnotify_obtain_group took a reference to group, we put this when we kill the file in the end */
-	grp_num = (INOTIFY_GROUP_NUM - atomic_inc_return(&inotify_grp_num));
-	group = fsnotify_obtain_group(grp_num, 0, &inotify_fsnotify_ops);
+	group = fsnotify_obtain_group(0, &inotify_fsnotify_ops);
 	if (IS_ERR(group))
 		return group;
 

include/linux/fsnotify_backend.h

@@ -60,12 +60,6 @@
 
 #define FS_MOVE			(FS_MOVED_FROM | FS_MOVED_TO)
 
-/* listeners that hard code group numbers near the top */
-#define DNOTIFY_GROUP_NUM	UINT_MAX
-#define AUDIT_WATCH_GROUP_NUM	(DNOTIFY_GROUP_NUM-1)
-#define AUDIT_TREE_GROUP_NUM	(AUDIT_WATCH_GROUP_NUM-1)
-#define INOTIFY_GROUP_NUM	(AUDIT_TREE_GROUP_NUM-1)
-
 struct fsnotify_group;
 struct fsnotify_event;
 struct fsnotify_mark_entry;
@@ -124,7 +118,6 @@ struct fsnotify_group {
 	 * closed.
 	 */
 	atomic_t refcnt;		/* things with interest in this group */
-	unsigned int group_num;		/* simply prevents accidental group collision */
 
 	const struct fsnotify_ops *ops;	/* how this group handles things */
 
@@ -312,8 +305,7 @@ static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode
 /* must call when a group changes its ->mask */
 extern void fsnotify_recalc_global_mask(void);
 /* get a reference to an existing or create a new group */
-extern struct fsnotify_group *fsnotify_obtain_group(unsigned int group_num,
-						    __u32 mask,
+extern struct fsnotify_group *fsnotify_obtain_group(__u32 mask,
 						    const struct fsnotify_ops *ops);
 /* run all marks associated with this group and update group->mask */
 extern void fsnotify_recalc_group_mask(struct fsnotify_group *group);

kernel/audit_tree.c

@@ -937,8 +937,7 @@ static int __init audit_tree_init(void)
 {
 	int i;
 
-	audit_tree_group = fsnotify_obtain_group(AUDIT_TREE_GROUP_NUM,
-						 0, &audit_tree_ops);
+	audit_tree_group = fsnotify_obtain_group(0, &audit_tree_ops);
 	if (IS_ERR(audit_tree_group))
 		audit_panic("cannot initialize fsnotify group for rectree watches");
 

kernel/audit_watch.c

@@ -577,7 +577,7 @@ static const struct fsnotify_ops audit_watch_fsnotify_ops = {
 
 static int __init audit_watch_init(void)
 {
-	audit_watch_group = fsnotify_obtain_group(AUDIT_WATCH_GROUP_NUM, AUDIT_FS_WATCH,
+	audit_watch_group = fsnotify_obtain_group(AUDIT_FS_WATCH,
 						  &audit_watch_fsnotify_ops);
 	if (IS_ERR(audit_watch_group)) {
 		audit_watch_group = NULL;