fs: push rcu_barrier() from deactivate_locked_super() to filesystems

There's no reason to call rcu_barrier() on every
deactivate_locked_super().  We only need to make sure that all delayed rcu
free inodes are flushed before we destroy related cache.

Removing rcu_barrier() from deactivate_locked_super() affects some fast
paths.  E.g.  on my machine exit_group() of a last process in IPC
namespace takes 0.07538s.  rcu_barrier() takes 0.05188s of that time.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 6 insertions, 0 deletions

diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c
index 9b627c15010a..34fcde765d24 100644
--- a/fs/ecryptfs/main.c
+++ b/fs/ecryptfs/main.c
@@ -710,6 +710,12 @@ static void ecryptfs_free_kmem_caches(void)
 {
         int i;
 
+        /*
+         * Make sure all delayed rcu free inodes are flushed before we
+         * destroy cache.
+         */
+        rcu_barrier();
+
         for (i = 0; i < ARRAY_SIZE(ecryptfs_cache_infos); i++) {
                 struct ecryptfs_cache_info *info;