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block/null_blk: Fix double blk_mq_start_request() warning

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When CONFIG_BLK_DEV_NULL_BLK_FAULT_INJECTION is enabled, null_queue_rq()
would return BLK_STS_RESOURCE or BLK_STS_DEV_RESOURCE for the request,
which has been marked as MQ_RQ_IN_FLIGHT by blk_mq_start_request().

Then null_queue_rqs() put these requests in the rqlist, return back to
the block layer core, which would try to queue them individually again,
so the warning in blk_mq_start_request() triggered.

Fix it by splitting the null_queue_rq() into two parts: the first is the
preparation of request, the second is the handling of request. We put
the blk_mq_start_request() after the preparation part, which may fail
and return back to the block layer core.

The throttling also belongs to the preparation part, so move it before
blk_mq_start_request(). And change the return type of null_handle_cmd()
to void, since it always return BLK_STS_OK now.

Reported-by:  <syzbot+fcc47ba2476570cbbeb0@syzkaller.appspotmail.com>
Closes: https://lore.kernel.org/all/0000000000000e6aac06098aee0c@google.com/
Fixes: d78bfa1346 ("block/null_blk: add queue_rqs() support")
Suggested-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Link: https://lore.kernel.org/r/20231120032521.1012037-1-chengming.zhou@linux.dev
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Chengming Zhou 2023-11-20 03:25:21 +00:00 committed by Jens Axboe
parent c96b817552
commit 53f2bca260
1 changed files with 13 additions and 12 deletions
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25
drivers/block/null_blk/main.c
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@ -1464,19 +1464,13 @@ blk_status_t null_process_cmd(struct nullb_cmd *cmd, enum req_op op,
return BLK_STS_OK;
}
static blk_status_t null_handle_cmd(struct nullb_cmd *cmd, sector_t sector,
sector_t nr_sectors, enum req_op op)
static void null_handle_cmd(struct nullb_cmd *cmd, sector_t sector,
sector_t nr_sectors, enum req_op op)
{
struct nullb_device *dev = cmd->nq->dev;
struct nullb *nullb = dev->nullb;
blk_status_t sts;
if (test_bit(NULLB_DEV_FL_THROTTLED, &dev->flags)) {
sts = null_handle_throttled(cmd);
if (sts != BLK_STS_OK)
return sts;
}
if (op == REQ_OP_FLUSH) {
cmd->error = errno_to_blk_status(null_handle_flush(nullb));
goto out;
@ -1493,7 +1487,6 @@ static blk_status_t null_handle_cmd(struct nullb_cmd *cmd, sector_t sector,
out:
nullb_complete_cmd(cmd);
return BLK_STS_OK;
}
static enum hrtimer_restart nullb_bwtimer_fn(struct hrtimer *timer)
@ -1724,8 +1717,6 @@ static blk_status_t null_queue_rq(struct blk_mq_hw_ctx *hctx,
cmd->fake_timeout = should_timeout_request(rq) ||
blk_should_fake_timeout(rq->q);
blk_mq_start_request(rq);
if (should_requeue_request(rq)) {
/*
* Alternate between hitting the core BUSY path, and the
@ -1738,6 +1729,15 @@ static blk_status_t null_queue_rq(struct blk_mq_hw_ctx *hctx,
return BLK_STS_OK;
}
if (test_bit(NULLB_DEV_FL_THROTTLED, &nq->dev->flags)) {
blk_status_t sts = null_handle_throttled(cmd);
if (sts != BLK_STS_OK)
return sts;
}
blk_mq_start_request(rq);
if (is_poll) {
spin_lock(&nq->poll_lock);
list_add_tail(&rq->queuelist, &nq->poll_list);
@ -1747,7 +1747,8 @@ static blk_status_t null_queue_rq(struct blk_mq_hw_ctx *hctx,
if (cmd->fake_timeout)
return BLK_STS_OK;
return null_handle_cmd(cmd, sector, nr_sectors, req_op(rq));
null_handle_cmd(cmd, sector, nr_sectors, req_op(rq));
return BLK_STS_OK;
}
static void null_queue_rqs(struct request **rqlist)