Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:17659 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726869AbeKUOBo (ORCPT ); Wed, 21 Nov 2018 09:01:44 -0500 From: Ming Lei To: Jens Axboe Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Theodore Ts'o , Omar Sandoval , Sagi Grimberg , Dave Chinner , Kent Overstreet , Mike Snitzer , dm-devel@redhat.com, Alexander Viro , linux-fsdevel@vger.kernel.org, Shaohua Li , linux-raid@vger.kernel.org, David Sterba , linux-btrfs@vger.kernel.org, "Darrick J . Wong" , linux-xfs@vger.kernel.org, Gao Xiang , Christoph Hellwig , linux-ext4@vger.kernel.org, Coly Li , linux-bcache@vger.kernel.org, Boaz Harrosh , Bob Peterson , cluster-devel@redhat.com, Ming Lei Subject: [PATCH V11 18/19] block: kill QUEUE_FLAG_NO_SG_MERGE Date: Wed, 21 Nov 2018 11:23:26 +0800 Message-Id: <20181121032327.8434-19-ming.lei@redhat.com> In-Reply-To: <20181121032327.8434-1-ming.lei@redhat.com> References: <20181121032327.8434-1-ming.lei@redhat.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: Since bdced438acd83ad83a6c ("block: setup bi_phys_segments after splitting"), physical segment number is mainly figured out in blk_queue_split() for fast path, and the flag of BIO_SEG_VALID is set there too. Now only blk_recount_segments() and blk_recalc_rq_segments() use this flag. Basically blk_recount_segments() is bypassed in fast path given BIO_SEG_VALID is set in blk_queue_split(). For another user of blk_recalc_rq_segments(): - run in partial completion branch of blk_update_request, which is an unusual case - run in blk_cloned_rq_check_limits(), still not a big problem if the flag is killed since dm-rq is the only user. Multi-page bvec is enabled now, not doing S/G merging is rather pointless with the current setup of the I/O path, as it isn't going to save you a significant amount of cycles. Reviewed-by: Christoph Hellwig Reviewed-by: Omar Sandoval Signed-off-by: Ming Lei --- block/blk-merge.c | 31 ++++++------------------------- block/blk-mq-debugfs.c | 1 - block/blk-mq.c | 3 --- drivers/md/dm-table.c | 13 ------------- include/linux/blkdev.h | 1 - 5 files changed, 6 insertions(+), 43 deletions(-) diff --git a/block/blk-merge.c b/block/blk-merge.c index 7c44216c1b58..8fcac7855a45 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -343,8 +343,7 @@ void blk_queue_split(struct request_queue *q, struct bio **bio) EXPORT_SYMBOL(blk_queue_split); static unsigned int __blk_recalc_rq_segments(struct request_queue *q, - struct bio *bio, - bool no_sg_merge) + struct bio *bio) { struct bio_vec bv, bvprv = { NULL }; int cluster, prev = 0; @@ -371,13 +370,6 @@ static unsigned int __blk_recalc_rq_segments(struct request_queue *q, nr_phys_segs = 0; for_each_bio(bio) { bio_for_each_bvec(bv, bio, iter) { - /* - * If SG merging is disabled, each bio vector is - * a segment - */ - if (no_sg_merge) - goto new_segment; - if (prev && cluster) { if (seg_size + bv.bv_len > queue_max_segment_size(q)) @@ -412,27 +404,16 @@ static unsigned int __blk_recalc_rq_segments(struct request_queue *q, void blk_recalc_rq_segments(struct request *rq) { - bool no_sg_merge = !!test_bit(QUEUE_FLAG_NO_SG_MERGE, - &rq->q->queue_flags); - - rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio, - no_sg_merge); + rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio); } void blk_recount_segments(struct request_queue *q, struct bio *bio) { - unsigned short seg_cnt = bio_segments(bio); - - if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) && - (seg_cnt < queue_max_segments(q))) - bio->bi_phys_segments = seg_cnt; - else { - struct bio *nxt = bio->bi_next; + struct bio *nxt = bio->bi_next; - bio->bi_next = NULL; - bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, false); - bio->bi_next = nxt; - } + bio->bi_next = NULL; + bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio); + bio->bi_next = nxt; bio_set_flag(bio, BIO_SEG_VALID); } diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c index a32bb79d6c95..d752fe4461af 100644 --- a/block/blk-mq-debugfs.c +++ b/block/blk-mq-debugfs.c @@ -127,7 +127,6 @@ static const char *const blk_queue_flag_name[] = { QUEUE_FLAG_NAME(SAME_FORCE), QUEUE_FLAG_NAME(DEAD), QUEUE_FLAG_NAME(INIT_DONE), - QUEUE_FLAG_NAME(NO_SG_MERGE), QUEUE_FLAG_NAME(POLL), QUEUE_FLAG_NAME(WC), QUEUE_FLAG_NAME(FUA), diff --git a/block/blk-mq.c b/block/blk-mq.c index 32b246ed44c0..0375c3bd410e 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2755,9 +2755,6 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set, q->queue_flags |= QUEUE_FLAG_MQ_DEFAULT; - if (!(set->flags & BLK_MQ_F_SG_MERGE)) - blk_queue_flag_set(QUEUE_FLAG_NO_SG_MERGE, q); - q->sg_reserved_size = INT_MAX; INIT_DELAYED_WORK(&q->requeue_work, blk_mq_requeue_work); diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c index 844f7d0f2ef8..a41832cf0c98 100644 --- a/drivers/md/dm-table.c +++ b/drivers/md/dm-table.c @@ -1698,14 +1698,6 @@ static int device_is_not_random(struct dm_target *ti, struct dm_dev *dev, return q && !blk_queue_add_random(q); } -static int queue_supports_sg_merge(struct dm_target *ti, struct dm_dev *dev, - sector_t start, sector_t len, void *data) -{ - struct request_queue *q = bdev_get_queue(dev->bdev); - - return q && !test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags); -} - static bool dm_table_all_devices_attribute(struct dm_table *t, iterate_devices_callout_fn func) { @@ -1902,11 +1894,6 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q, if (!dm_table_supports_write_zeroes(t)) q->limits.max_write_zeroes_sectors = 0; - if (dm_table_all_devices_attribute(t, queue_supports_sg_merge)) - blk_queue_flag_clear(QUEUE_FLAG_NO_SG_MERGE, q); - else - blk_queue_flag_set(QUEUE_FLAG_NO_SG_MERGE, q); - dm_table_verify_integrity(t); /* diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index a281b6737b61..8e05966ffe94 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -590,7 +590,6 @@ struct request_queue { #define QUEUE_FLAG_SAME_FORCE 15 /* force complete on same CPU */ #define QUEUE_FLAG_DEAD 16 /* queue tear-down finished */ #define QUEUE_FLAG_INIT_DONE 17 /* queue is initialized */ -#define QUEUE_FLAG_NO_SG_MERGE 18 /* don't attempt to merge SG segments*/ #define QUEUE_FLAG_POLL 19 /* IO polling enabled if set */ #define QUEUE_FLAG_WC 20 /* Write back caching */ #define QUEUE_FLAG_FUA 21 /* device supports FUA writes */ -- 2.9.5