From 110fdb4486d3a5e67d55bc6866d6426e6d49ccfc Mon Sep 17 00:00:00 2001 From: Pankaj Raghav Date: Thu, 29 Sep 2022 16:41:41 +0200 Subject: [PATCH] block: add rationale for not using blk_mq_plug() when applicable There are two places in the block layer at the moment where blk_mq_plug() helper could be used instead of directly accessing the plug from struct current. In both these cases, directly accessing the plug should not have any consequences for zoned devices. Make the intent explicit by adding comments instead of introducing unwanted checks with blk_mq_plug() helper.[1] [1] https://lore.kernel.org/linux-block/f6e54907-1035-2b2c-6387-ed178be05ccb@kernel.dk/ Signed-off-by: Pankaj Raghav Suggested-by: Jens Axboe Link: https://lore.kernel.org/r/20220929144141.140077-1-p.raghav@samsung.com [axboe: fixup multi-line comment style] Signed-off-by: Jens Axboe --- block/blk-core.c | 6 ++++++ block/blk-mq.c | 6 ++++++ 2 files changed, 12 insertions(+) diff --git a/block/blk-core.c b/block/blk-core.c index dc1fa454ae30..4bfc0d504b2d 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -850,6 +850,12 @@ int bio_poll(struct bio *bio, struct io_comp_batch *iob, unsigned int flags) !test_bit(QUEUE_FLAG_POLL, &q->queue_flags)) return 0; + /* + * As the requests that require a zone lock are not plugged in the + * first place, directly accessing the plug instead of using + * blk_mq_plug() should not have any consequences during flushing for + * zoned devices. + */ blk_flush_plug(current->plug, false); if (bio_queue_enter(bio)) diff --git a/block/blk-mq.c b/block/blk-mq.c index b2b318df4f69..9dd3ec42613f 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1215,6 +1215,12 @@ void blk_execute_rq_nowait(struct request *rq, bool at_head) WARN_ON(!blk_rq_is_passthrough(rq)); blk_account_io_start(rq); + + /* + * As plugging can be enabled for passthrough requests on a zoned + * device, directly accessing the plug instead of using blk_mq_plug() + * should not have any consequences. + */ if (current->plug) blk_add_rq_to_plug(current->plug, rq); else