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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Mark Syms <mark.syms@citrix.com>,
        Andreas Gruenbacher <agruenba@redhat.com>,
        Bob Peterson <rpeterso@redhat.com>
Subject: [PATCH 4.20 165/171] gfs2: Fix missed wakeups in find_insert_glock
Date:   Tue, 12 Mar 2019 10:09:05 -0700
Message-Id: <20190312170401.640154262@linuxfoundation.org>
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4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

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);
 }