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, 5 insertions, 0 deletions

diff --git a/fs/ceph/super.c b/fs/ceph/super.c
index b982239f38f..3a42d932637 100644
--- a/fs/ceph/super.c
+++ b/fs/ceph/super.c
@@ -603,6 +603,11 @@ bad_cap:
 
 static void destroy_caches(void)
 {
+        /*
+         * Make sure all delayed rcu free inodes are flushed before we
+         * destroy cache.
+         */
+        rcu_barrier();
         kmem_cache_destroy(ceph_inode_cachep);
         kmem_cache_destroy(ceph_cap_cachep);
         kmem_cache_destroy(ceph_dentry_cachep);