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. However, there are still some problems if the request is
started, and this will be fixed in next patch.
Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
drivers/block/nbd.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 5170a630778d..920da390635c 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -718,12 +718,13 @@ 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);
@@ -785,6 +786,9 @@ 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:
+ if (req)
+ blk_mq_put_rq_ref(req);
return ret ? ERR_PTR(ret) : cmd;
}
--
2.31.1
