gfs2: Fix glock rhashtable rcu bug

commit 961ae1d83d055a4b9ebbfb4cc8ca62ec1a7a3b74 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 9cd8c92b953d164294fcc48a5bc5e4a415732fd4..070901e76653a306a2c961c5a5b8bafcd40157ca 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 be519416c11231ffe06a2bc12c41ea1cebf4de2f..4a9077ec931366df03a96efa6491befb800ee4f5 100644 (file)
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -367,6 +367,7 @@ struct gfs2_glock {
                        loff_t end;
                } gl_vm;
        };
+       struct rcu_head gl_rcu;
        struct rhash_head gl_node;
 };