[PATCHv2 2/2] blk-mq: allow cached requests to be used for flush operations

[Keith Busch <kbusch@meta.com>]

From: Keith Busch <kbusch@kernel.org>

The cached request lookups reject a request whose op_is_flush() state does
not match the incoming operation. That check is from when rq->elv and
rq->flush shared a union, so a request could not be both a scheduler
request and carry flush state. Commit be4c427809b0 ("blk-mq: use the I/O
scheduler for writes from the flush state machine") made them separate
members of struct request.

A cached request now gets its scheduler state when it is claimed by an
operation, so one claimed for a flush is set up exactly as a freshly
allocated request. Drop the check so a cached batch can mix flush and
non-flush operations.

Signed-off-by: Keith Busch <kbusch@kernel.org>
---
 block/blk-mq.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 5df6d2244db82..025a799f35b92 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -661,8 +661,6 @@ static struct request *blk_mq_alloc_cached_request(struct request_queue *q,
 
 		if (blk_mq_get_hctx_type(opf) != rq->mq_hctx->type)
 			return NULL;
-		if (op_is_flush(rq->cmd_flags) != op_is_flush(opf))
-			return NULL;
 
 		rq_list_pop(&plug->cached_rqs);
 		rq->cmd_flags = opf;
@@ -3075,8 +3073,6 @@ static struct request *blk_mq_get_cached_request(struct blk_plug *plug,
 	if (type != rq->mq_hctx->type &&
 	    (type != HCTX_TYPE_READ || rq->mq_hctx->type != HCTX_TYPE_DEFAULT))
 		return NULL;
-	if (op_is_flush(rq->cmd_flags) != op_is_flush(opf))
-		return NULL;
 	rq_list_pop(&plug->cached_rqs);
 	return rq;
 }
-- 
2.52.0