[PATCH 5.0 17/25] gfs2: Fix missed wakeups in find_insert_glock

Greg Kroah-Hartman
2019-03-12T18:13:38Z

From: Andreas Gruenbacher <agruenba@redhat.com>

commit 605b0487f0bc1ae9963bf52ece0f5c8055186f81 upstream.

Mark Syms has reported seeing tasks that are stuck waiting in
find_insert_glock. It turns out that struct lm_lockname contains four padding
bytes on 64-bit architectures that function glock_waitqueue doesn't skip when
hashing the glock name. As a result, we can end up waking up the wrong
waitqueue, and the waiting tasks may be stuck forever.

Fix that by using ht_parms.key_len instead of sizeof(struct lm_lockname) for
the key length.

Reported-by: Mark Syms <mark.syms@citrix.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>

---
fs/gfs2/glock.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -107,7 +107,7 @@ static int glock_wake_function(wait_queu

static wait_queue_head_t *glock_waitqueue(struct lm_lockname *name)
{
- u32 hash = jhash2((u32 *)name, sizeof(*name) / 4, 0);
+ u32 hash = jhash2((u32 *)name, ht_parms.key_len / 4, 0);

return glock_wait_table + hash_32(hash, GLOCK_WAIT_TABLE_BITS);
}