[PATCH v4 01/14] blk-mq: avoid sleep in blk_mq_alloc_request_hctx

[Kemeng Shi]

Commit 1f5bd336b9150 ("blk-mq: add blk_mq_alloc_request_hctx") add
blk_mq_alloc_request_hctx to send commands to a specific queue. If
BLK_MQ_REQ_NOWAIT is not set in tag allocation, we may change to different
hctx after sleep and get tag from unexpected hctx. So BLK_MQ_REQ_NOWAIT
must be set in flags for blk_mq_alloc_request_hctx.
After commit 600c3b0cea784 ("blk-mq: open code __blk_mq_alloc_request in
blk_mq_alloc_request_hctx"), blk_mq_alloc_request_hctx return -EINVAL
if both BLK_MQ_REQ_NOWAIT and BLK_MQ_REQ_RESERVED are not set instead of
if BLK_MQ_REQ_NOWAIT is not set. So if BLK_MQ_REQ_NOWAIT is not set and
BLK_MQ_REQ_RESERVED is set, blk_mq_alloc_request_hctx could alloc tag
from unexpected hctx. I guess what we need here is that return -EINVAL
if either BLK_MQ_REQ_NOWAIT or BLK_MQ_REQ_RESERVED is not set.

Currently both BLK_MQ_REQ_NOWAIT and BLK_MQ_REQ_RESERVED will be set if
specific hctx is needed in nvme_auth_submit, nvmf_connect_io_queue
and nvmf_connect_admin_queue. Fix the potential BLK_MQ_REQ_NOWAIT missed
case in future.

Fixes: 600c3b0cea78 ("blk-mq: open code __blk_mq_alloc_request in blk_mq_alloc_request_hctx")
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>
---
 block/blk-mq.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 2c49b4151da1..9c6a6ce9eaf2 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -658,7 +658,8 @@ struct request *blk_mq_alloc_request_hctx(struct request_queue *q,
 	 * allocator for this for the rare use case of a command tied to
 	 * a specific queue.
 	 */
-	if (WARN_ON_ONCE(!(flags & (BLK_MQ_REQ_NOWAIT | BLK_MQ_REQ_RESERVED))))
+	if (WARN_ON_ONCE(!(flags & BLK_MQ_REQ_NOWAIT)) ||
+	    WARN_ON_ONCE(!(flags & BLK_MQ_REQ_RESERVED)))
 		return ERR_PTR(-EINVAL);
 
 	if (hctx_idx >= q->nr_hw_queues)
-- 
2.30.0