block: bypass ->make_request_fn for blk-mq drivers
authorChristoph Hellwig <hch@lst.de>
Sat, 25 Apr 2020 07:53:36 +0000 (09:53 +0200)
committerJens Axboe <axboe@kernel.dk>
Sat, 25 Apr 2020 15:45:44 +0000 (09:45 -0600)
commit8cf7961dab42c9177a556b719c15f5b9449c24d1
treecf0e7e5d0b7f6f0ee665629b61fc91cc56ed77c7
parentae3cc8d8ff061d3ffca96665685550e70a86472a
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 <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
block/blk-core.c
block/blk-mq.c
drivers/md/dm.c
include/linux/blk-mq.h