[patch added to 3.12-stable] FS-Cache: Increase reference of parent after registering, netfs success

[Jiri Slaby <jslaby@suse.cz>]

From: Kinglong Mee <kinglongmee@gmail.com>

This patch has been added to the 3.12 stable tree. If you have any
objections, please let us know.

===============

commit 86108c2e34a26e4bec3c6ddb23390bf8cedcf391 upstream.

If netfs exist, fscache should not increase the reference of parent's
usage and n_children, otherwise, never be decreased.

v2: thanks David's suggest,
 move increasing reference of parent if success
 use kmem_cache_free() freeing primary_index directly

v3: don't move "netfs->primary_index->parent = &fscache_fsdef_index;"

Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 fs/fscache/netfs.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/fs/fscache/netfs.c b/fs/fscache/netfs.c
index b1bb6117473a..04e18d28013b 100644
--- a/fs/fscache/netfs.c
+++ b/fs/fscache/netfs.c
@@ -46,9 +46,6 @@ int __fscache_register_netfs(struct fscache_netfs *netfs)
 	netfs->primary_index->parent		= &fscache_fsdef_index;
 	netfs->primary_index->netfs_data	= netfs;
 
-	atomic_inc(&netfs->primary_index->parent->usage);
-	atomic_inc(&netfs->primary_index->parent->n_children);
-
 	spin_lock_init(&netfs->primary_index->lock);
 	INIT_HLIST_HEAD(&netfs->primary_index->backing_objects);
 
@@ -61,6 +58,9 @@ int __fscache_register_netfs(struct fscache_netfs *netfs)
 			goto already_registered;
 	}
 
+	atomic_inc(&netfs->primary_index->parent->usage);
+	atomic_inc(&netfs->primary_index->parent->n_children);
+
 	list_add(&netfs->link, &fscache_netfs_list);
 	ret = 0;
 
@@ -71,8 +71,7 @@ already_registered:
 	up_write(&fscache_addremove_sem);
 
 	if (ret < 0) {
-		netfs->primary_index->parent = NULL;
-		__fscache_cookie_put(netfs->primary_index);
+		kmem_cache_free(fscache_cookie_jar, netfs->primary_index);
 		netfs->primary_index = NULL;
 	}
 
-- 
2.7.1