From: chengming.zhou@linux.dev
To: axboe@kernel.dk, bvanassche@acm.org
Cc: kch@nvidia.com, damien.lemoal@opensource.wdc.com,
ming.lei@redhat.com, zhouchengming@bytedance.com,
justinstitt@google.com, shinichiro.kawasaki@wdc.com,
akinobu.mita@gmail.com, linux-block@vger.kernel.org,
linux-kernel@vger.kernel.org, chengming.zhou@linux.dev,
syzbot+fcc47ba2476570cbbeb0@syzkaller.appspotmail.com
Subject: [PATCH] block/null_blk: Fix double blk_mq_start_request() warning
Date: Mon, 20 Nov 2023 03:25:21 +0000 [thread overview]
Message-ID: <20231120032521.1012037-1-chengming.zhou@linux.dev> (raw)
From: Chengming Zhou <zhouchengming@bytedance.com>
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: d78bfa1346ab ("block/null_blk: add queue_rqs() support")
Suggested-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
---
drivers/block/null_blk/main.c | 25 +++++++++++++------------
1 file changed, 13 insertions(+), 12 deletions(-)
diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index 22a3cf7f32e2..3021d58ca51c 100644
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -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)
--
2.40.1
next reply other threads:[~2023-11-20 3:26 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-20 3:25 chengming.zhou [this message]
2023-11-20 17:26 ` [PATCH] block/null_blk: Fix double blk_mq_start_request() warning Jens Axboe
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