[PATCH 4.2.y-ckt 57/93] dm cache metadata: fix cmd_read_lock() acquiring write lock

[Kamal Mostafa]

4.2.8-ckt9 -stable review patch.  If anyone has any objections, please let me 
know.

---8<------------------------------------------------------------

From: Ahmed Samy <f.falle...@gmail.com>

commit 6545b60baaf880b0cd29a5e89dbe745a06027e89 upstream.

Commit 9567366fefdd ("dm cache metadata: fix READ_LOCK macros and
cleanup WRITE_LOCK macros") uses down_write() instead of down_read() in
cmd_read_lock(), yet up_read() is used to release the lock in
READ_UNLOCK().  Fix it.

Fixes: 9567366fefdd ("dm cache metadata: fix READ_LOCK macros and cleanup 
WRITE_LOCK macros")
Signed-off-by: Ahmed Samy <f.falle...@gmail.com>
Signed-off-by: Mike Snitzer <snit...@redhat.com>
Signed-off-by: Kamal Mostafa <ka...@canonical.com>
---
 drivers/md/dm-cache-metadata.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/md/dm-cache-metadata.c b/drivers/md/dm-cache-metadata.c
index 141b9bc..d00d5bb 100644
--- a/drivers/md/dm-cache-metadata.c
+++ b/drivers/md/dm-cache-metadata.c
@@ -890,9 +890,9 @@ static bool cmd_write_lock(struct dm_cache_metadata *cmd)
 
 static bool cmd_read_lock(struct dm_cache_metadata *cmd)
 {
-       down_write(&cmd->root_lock);
+       down_read(&cmd->root_lock);
        if (cmd->fail_io) {
-               up_write(&cmd->root_lock);
+               up_read(&cmd->root_lock);
                return false;
        }
        return true;
-- 
2.7.4