gfs2: Add missing rcu locking for glock lookup

commit f38e5fb95a1f8feda88531eedc98f69b24748712 upstream.

We must hold the rcu read lock across looking up glocks and trying to
bump their refcount to prevent the glocks from being freed in between.

Signed-off-by: Andrew Price <anprice@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 14cbf60167a7..133f322573b5 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -658,9 +658,11 @@ int gfs2_glock_get(struct gfs2_sbd *sdp, u64 number,
         struct kmem_cache *cachep;
         int ret, tries = 0;
 
+        rcu_read_lock();
         gl = rhashtable_lookup_fast(&gl_hash_table, &name, ht_parms);
         if (gl && !lockref_get_not_dead(&gl->gl_lockref))
                 gl = NULL;
+        rcu_read_unlock();
 
         *glp = gl;
         if (gl)
@@ -728,15 +730,18 @@ again:
 
         if (ret == -EEXIST) {
                 ret = 0;
+                rcu_read_lock();
                 tmp = rhashtable_lookup_fast(&gl_hash_table, &name, ht_parms);
                 if (tmp == NULL || !lockref_get_not_dead(&tmp->gl_lockref)) {
                         if (++tries < 100) {
+                                rcu_read_unlock();
                                 cond_resched();
                                 goto again;
                         }
                         tmp = NULL;
                         ret = -ENOMEM;
                 }
+                rcu_read_unlock();
         } else {
                 WARN_ON_ONCE(ret);
         }