ext4: Use rcu_barrier() on module unload.

The ext4 module uses rcu_call() thus it should use rcu_barrier()on
module unload.

The kmem cache ext4_pspace_cachep is sometimes free'ed using
call_rcu() callbacks.  Thus, we must wait for completion of call_rcu()
before doing kmem_cache_destroy().

Signed-off-by: Jesper Dangaard Brouer <hawk@comx.dk>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 5 insertions, 1 deletions

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 4a45efabb203..2fcaf286f1de 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2909,7 +2909,11 @@ int __init init_ext4_mballoc(void)
 
 void exit_ext4_mballoc(void)
 {
-        /* XXX: synchronize_rcu(); */
+        /* 
+         * Wait for completion of call_rcu()'s on ext4_pspace_cachep
+         * before destroying the slab cache.
+         */
+        rcu_barrier();
         kmem_cache_destroy(ext4_pspace_cachep);
         kmem_cache_destroy(ext4_ac_cachep);
         kmem_cache_destroy(ext4_free_ext_cachep);