From 2516c246d01c23a5f5310e9ac78d9f8aad9b1d0e Mon Sep 17 00:00:00 2001 From: Keith Busch Date: Fri, 14 Nov 2025 10:31:45 -0800 Subject: [PATCH] block: consider discard merge last If the next discard range is contiguous with the current range being considered, it's cheaper to expand the current range than to append an additional bio. Signed-off-by: Keith Busch Reviewed-by: Chaitanya Kulkarni Signed-off-by: Jens Axboe --- block/blk-merge.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/block/blk-merge.c b/block/blk-merge.c index d3115d7469df0..db08bc9060916 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -712,10 +712,10 @@ static void blk_account_io_merge_request(struct request *req) static enum elv_merge blk_try_req_merge(struct request *req, struct request *next) { - if (blk_discard_mergable(req)) - return ELEVATOR_DISCARD_MERGE; - else if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next)) + if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next)) return ELEVATOR_BACK_MERGE; + else if (blk_discard_mergable(req)) + return ELEVATOR_DISCARD_MERGE; return ELEVATOR_NO_MERGE; } @@ -903,12 +903,12 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio) enum elv_merge blk_try_merge(struct request *rq, struct bio *bio) { - if (blk_discard_mergable(rq)) - return ELEVATOR_DISCARD_MERGE; - else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector) + if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector) return ELEVATOR_BACK_MERGE; else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector) return ELEVATOR_FRONT_MERGE; + else if (blk_discard_mergable(rq)) + return ELEVATOR_DISCARD_MERGE; return ELEVATOR_NO_MERGE; } -- 2.47.3