This lockdep splat was being triggered on umount:
[55715.973122] ===============================
[55715.980169] [ INFO: suspicious RCU usage. ]
[55715.981021] 4.3.0-11553-g8d3de01-dirty #15 Tainted: G W
[55715.982353] -------------------------------
[55715.983301] fs/gfs2/glock.c:1427 suspicious rcu_dereference_protected()
usage!
The code it refers to is the rht_for_each_entry_safe usage in
glock_hash_walk. The condition that triggers the warning is
lockdep_rht_bucket_is_held(tbl, hash) which is checked in the
__rcu_dereference_protected macro.
The rhashtable buckets are not changed in glock_hash_walk so it's safe
to rely on the rcu protection. Replace the rht_for_each_entry_safe()
usage with rht_for_each_entry_rcu(), which doesn't care whether the
bucket lock is held if the rcu read lock is held.
Signed-off-by: Andrew Price <anpr...@redhat.com>
---
fs/gfs2/glock.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 32e7471..430326e 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -1417,14 +1417,14 @@ static struct shrinker glock_shrinker = {
static void glock_hash_walk(glock_examiner examiner, const struct gfs2_sbd
*sdp)
{
struct gfs2_glock *gl;
- struct rhash_head *pos, *next;
+ struct rhash_head *pos;
const struct bucket_table *tbl;
int i;
rcu_read_lock();
tbl = rht_dereference_rcu(gl_hash_table.tbl, &gl_hash_table);
for (i = 0; i < tbl->size; i++) {
- rht_for_each_entry_safe(gl, pos, next, tbl, i, gl_node) {
+ rht_for_each_entry_rcu(gl, pos, tbl, i, gl_node) {
if ((gl->gl_name.ln_sbd == sdp) &&
lockref_get_not_dead(&gl->gl_lockref))
examiner(gl);
--
2.4.3
