From: Yu Kuai <yukuai3@huawei.com>
To: <axboe@kernel.dk>, <josef@toxicpanda.com>, <ming.lei@redhat.com>,
<hch@infradead.org>
Cc: <linux-block@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
<nbd@other.debian.org>, <yukuai3@huawei.com>,
<yi.zhang@huawei.com>
Subject: [PATCH v5 5/6] nbd: convert to use blk_mq_find_and_get_req()
Date: Thu, 9 Sep 2021 22:12:55 +0800 [thread overview]
Message-ID: <20210909141256.2606682-6-yukuai3@huawei.com> (raw)
In-Reply-To: <20210909141256.2606682-1-yukuai3@huawei.com>
blk_mq_tag_to_rq() can only ensure to return valid request in
following situation:
1) client send request message to server first
submit_bio
...
blk_mq_get_tag
...
blk_mq_get_driver_tag
...
nbd_queue_rq
nbd_handle_cmd
nbd_send_cmd
2) client receive respond message from server
recv_work
nbd_read_stat
blk_mq_tag_to_rq
If step 1) is missing, blk_mq_tag_to_rq() will return a stale
request, which might be freed. Thus convert to use
blk_mq_find_and_get_req() to make sure the returned request is not
freed.
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
---
drivers/block/nbd.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 6d8cbf8be231..d298e2b9e6ee 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -729,12 +729,13 @@ static struct nbd_cmd *nbd_read_stat(struct nbd_device *nbd, int index)
tag = nbd_handle_to_tag(handle);
hwq = blk_mq_unique_tag_to_hwq(tag);
if (hwq < nbd->tag_set.nr_hw_queues)
- req = blk_mq_tag_to_rq(nbd->tag_set.tags[hwq],
- blk_mq_unique_tag_to_tag(tag));
+ req = blk_mq_find_and_get_req(nbd->tag_set.tags[hwq],
+ blk_mq_unique_tag_to_tag(tag));
if (!req || !blk_mq_request_started(req)) {
dev_err(disk_to_dev(nbd->disk), "Unexpected reply (%d) %p\n",
tag, req);
- return ERR_PTR(-ENOENT);
+ ret = -ENOENT;
+ goto put_req;
}
trace_nbd_header_received(req, handle);
cmd = blk_mq_rq_to_pdu(req);
@@ -806,6 +807,14 @@ static struct nbd_cmd *nbd_read_stat(struct nbd_device *nbd, int index)
out:
trace_nbd_payload_received(req, handle);
mutex_unlock(&cmd->lock);
+put_req:
+ /*
+ * It's safe to drop refcnt here because request completion won't
+ * concurent, thus if nbd_read_stat() successd, the request refcnt
+ * won't drop to zero here.
+ */
+ if (req)
+ blk_mq_put_rq_ref(req);
return ret ? ERR_PTR(ret) : cmd;
}
--
2.31.1
next prev parent reply other threads:[~2021-09-09 14:03 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-09 14:12 [PATCH v5 0/6] handle unexpected message from server Yu Kuai
2021-09-09 14:12 ` [PATCH v5 1/6] nbd: don't handle response without a corresponding request message Yu Kuai
2021-09-14 0:54 ` Ming Lei
2021-09-09 14:12 ` [PATCH v5 2/6] nbd: make sure request completion won't concurrent Yu Kuai
2021-09-14 0:57 ` Ming Lei
2021-09-14 3:11 ` yukuai (C)
2021-09-09 14:12 ` [PATCH v5 3/6] nbd: check sock index in nbd_read_stat() Yu Kuai
2021-09-09 14:12 ` [PATCH v5 4/6] blk-mq: export two symbols to get request by tag Yu Kuai
2021-09-09 14:12 ` Yu Kuai [this message]
2021-09-14 1:11 ` [PATCH v5 5/6] nbd: convert to use blk_mq_find_and_get_req() Ming Lei
2021-09-14 3:11 ` yukuai (C)
2021-09-14 6:44 ` Ming Lei
2021-09-14 7:13 ` yukuai (C)
2021-09-14 7:46 ` Ming Lei
2021-09-14 9:08 ` yukuai (C)
2021-09-14 9:12 ` yukuai (C)
2021-09-14 14:33 ` Ming Lei
2021-09-14 9:19 ` yukuai (C)
2021-09-14 14:37 ` Ming Lei
2021-09-15 1:54 ` yukuai (C)
2021-09-15 3:16 ` Ming Lei
2021-09-15 3:36 ` yukuai (C)
2021-09-15 3:46 ` Ming Lei
2021-09-09 14:12 ` [PATCH v5 6/6] nbd: don't start request if nbd_queue_rq() failed Yu Kuai
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