Re: [PATCH] blk-mq: setup blk_mq_alloc_data.cmd_flags after submit_bio_checks() is done
From: Christoph Hellwig <hch@lst.de>
Date: 2021-11-12 08:21:44
On Fri, Nov 12, 2021 at 04:11:37PM +0800, Ming Lei wrote:
quoted hunk ↗ jump to hunk
@@ -2564,13 +2564,15 @@ static inline struct request *blk_mq_get_request(struct request_queue *q, if (blk_mq_attempt_bio_merge(q, bio, nsegs, same_queue_rq)) return NULL; + if (bio->bi_opf != rq->cmd_flags) + goto fallback;
I think this deserves a comment, as this means a read prealloc can only be used for reads, and no fua can be set if the preallocating I/O didn't use fua, etc. What are the pitfalls of just chanigng cmd_flags?