dm cache metadata: fix cmd_read_lock() acquiring write lock

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")
Cc: [e-mail]
Signed-off-by: Ahmed Samy <[e-mail]>
Signed-off-by: Mike Snitzer <[e-mail]>

drivers/md/dm-cache-metadata.c

···
 
 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;