block: null_blk: Fix handling of fake timeout request

When injecting a fake timeout into the null_blk driver using
fail_io_timeout, the request timeout handler does not execute
blk_mq_complete_request(), so the complete callback is never executed
for a timedout request.

The null_blk driver also has a driver-specific fake timeout mechanism
which does not have this problem. Fix the problem with fail_io_timeout
by using the same meachanism as null_blk internal timeout feature, using
the fake_timeout field of null_blk commands.

Reported-by: Akinobu Mita <akinobu.mita@gmail.com>
Fixes: de3510e ("null_blk: fix command timeout completion handling")
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20230314041106.19173-2-damien.lemoal@opensource.wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: Damien Le Moal

drivers/block/null_blk/main.c

@@ -1413,8 +1413,7 @@ static inline void nullb_complete_cmd(struct nullb_cmd *cmd)
 	case NULL_IRQ_SOFTIRQ:
 		switch (cmd->nq->dev->queue_mode) {
 		case NULL_Q_MQ:
-			if (likely(!blk_should_fake_timeout(cmd->rq->q)))
-				blk_mq_complete_request(cmd->rq);
+			blk_mq_complete_request(cmd->rq);
 			break;
 		case NULL_Q_BIO:
 			/*
@@ -1675,7 +1674,8 @@ static blk_status_t null_queue_rq(struct blk_mq_hw_ctx *hctx,
 	cmd->rq = bd->rq;
 	cmd->error = BLK_STS_OK;
 	cmd->nq = nq;
-	cmd->fake_timeout = should_timeout_request(bd->rq);
+	cmd->fake_timeout = should_timeout_request(bd->rq) ||
+		blk_should_fake_timeout(bd->rq->q);
 
 	blk_mq_start_request(bd->rq);