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 ec0848fcca02d8960ba671b9b0be5a56ed3fd7ed..6aa0a98dc8ac908077bdf5f048e3356c2d4f1d66 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 511e1ed7e2ded7b0a9dc9882cffe0b66c37c96a2..0530d9d56f4061100733c2b3792ac8e9370686e9 100644 (file)
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -370,6 +370,7 @@ struct gfs2_glock {
                        loff_t end;
                } gl_vm;
        };
+       struct rcu_head gl_rcu;
        struct rhash_head gl_node;
 };