gfs2: Fix glock rhashtable rcu bug

Before commit 88ffbf3e03 "GFS2: Use resizable hash table for glocks",
glocks were freed via call_rcu to allow reading the glock hashtable
locklessly using rcu.  This was then changed to free glocks immediately,
which made reading the glock hashtable unsafe.  Bring back the original
code for freeing glocks via call_rcu.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Cc: stable@vger.kernel.org # 4.3+

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 6cd71c50b8bdc7f21a90e4eb29c1ff5162b455ff..c38ab6c818983803d67815ac4a32b9302e48795d 100644 (file)
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -80,9 +80,9 @@ static struct rhashtable_params ht_parms = {
 
 static struct rhashtable gl_hash_table;
 
-void gfs2_glock_free(struct gfs2_glock *gl)
+static void gfs2_glock_dealloc(struct rcu_head *rcu)
 {
-       struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
+       struct gfs2_glock *gl = container_of(rcu, struct gfs2_glock, gl_rcu);
 
        if (gl->gl_ops->go_flags & GLOF_ASPACE) {
                kmem_cache_free(gfs2_glock_aspace_cachep, gl);
@@ -90,6 +90,13 @@ void gfs2_glock_free(struct gfs2_glock *gl)
                kfree(gl->gl_lksb.sb_lvbptr);
                kmem_cache_free(gfs2_glock_cachep, gl);
        }
+}
+
+void gfs2_glock_free(struct gfs2_glock *gl)
+{
+       struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
+
+       call_rcu(&gl->gl_rcu, gfs2_glock_dealloc);
        if (atomic_dec_and_test(&sdp->sd_glock_disposal))
                wake_up(&sdp->sd_glock_wait);
 }

diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index 790e73984288776140fb89036f46ca4dbd4ba837..73fce76e67ee84b49495389c44449738008a4312 100644 (file)
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -373,6 +373,7 @@ struct gfs2_glock {
                        loff_t end;
                } gl_vm;
        };
+       struct rcu_head gl_rcu;
        struct rhash_head gl_node;
 };