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 --- block/blk-core.c | 26 +++++++++++++++++--------- 1 file changed, 17 insertions(+), 9 deletions(-) (limited to 'block/blk-core.c') diff --git a/block/blk-core.c b/block/blk-core.c index 38e984d95e84..dffff2100888 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -1073,7 +1073,10 @@ blk_qc_t generic_make_request(struct bio *bio) /* Create a fresh bio_list for all subordinate requests */ bio_list_on_stack[1] = bio_list_on_stack[0]; bio_list_init(&bio_list_on_stack[0]); - ret = q->make_request_fn(q, bio); + if (q->make_request_fn) + ret = q->make_request_fn(q, bio); + else + ret = blk_mq_make_request(q, bio); blk_queue_exit(q); @@ -1113,9 +1116,7 @@ EXPORT_SYMBOL(generic_make_request); * * This function behaves like generic_make_request(), but does not protect * against recursion. Must only be used if the called driver is known - * to not call generic_make_request (or direct_make_request) again from - * its make_request function. (Calling direct_make_request again from - * a workqueue is perfectly fine as that doesn't recurse). + * to be blk-mq based. */ blk_qc_t direct_make_request(struct bio *bio) { @@ -1123,20 +1124,27 @@ blk_qc_t direct_make_request(struct bio *bio) bool nowait = bio->bi_opf & REQ_NOWAIT; blk_qc_t ret; + if (WARN_ON_ONCE(q->make_request_fn)) + goto io_error; if (!generic_make_request_checks(bio)) return BLK_QC_T_NONE; if (unlikely(blk_queue_enter(q, nowait ? BLK_MQ_REQ_NOWAIT : 0))) { if (nowait && !blk_queue_dying(q)) - bio_wouldblock_error(bio); - else - bio_io_error(bio); - return BLK_QC_T_NONE; + goto would_block; + goto io_error; } - ret = q->make_request_fn(q, bio); + ret = blk_mq_make_request(q, bio); blk_queue_exit(q); return ret; + +would_block: + bio_wouldblock_error(bio); + return BLK_QC_T_NONE; +io_error: + bio_io_error(bio); + return BLK_QC_T_NONE; } EXPORT_SYMBOL_GPL(direct_make_request); -- cgit v1.2.3