From 8cf7961dab42c9177a556b719c15f5b9449c24d1 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Sat, 25 Apr 2020 09:53:36 +0200 Subject: block: bypass ->make_request_fn for blk-mq drivers Call blk_mq_make_request when no ->make_request_fn is set. This is safe now that blk_alloc_queue always sets up the pointer for make_request based drivers. This avoids an indirect call in the blk-mq driver I/O fast path, which is rather expensive due to spectre mitigations. Signed-off-by: Christoph Hellwig Signed-off-by: Jens Axboe --- drivers/md/dm.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'drivers/md') diff --git a/drivers/md/dm.c b/drivers/md/dm.c index db9e46114653..0eb93da44ea2 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -1788,6 +1788,9 @@ static blk_qc_t dm_make_request(struct request_queue *q, struct bio *bio) int srcu_idx; struct dm_table *map; + if (dm_get_md_type(md) == DM_TYPE_REQUEST_BASED) + return blk_mq_make_request(q, bio); + map = dm_get_live_table(md, &srcu_idx); /* if we're suspended, we have to queue this io for later */ -- cgit v1.2.3