[PATCH V14 17/18] block: kill QUEUE_FLAG_NO_SG_MERGE
From: Ming Lei <hidden>
Date: 2019-01-21 08:22:34
Also in:
dm-devel, linux-bcache, linux-block, linux-btrfs, linux-ext4, linux-fsdevel, linux-mm, linux-xfs, lkml
Subsystem:
block layer, device-mapper (lvm), the rest · Maintainers:
Jens Axboe, Alasdair Kergon, Mike Snitzer, Mikulas Patocka, Benjamin Marzinski, Linus Torvalds
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 <hch@lst.de>
Reviewed-by: Omar Sandoval <redacted>
Signed-off-by: Ming Lei <redacted>
---
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 8a498f29636f..b990853f6de7 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c@@ -358,8 +358,7 @@ 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 prev = 0;
@@ -385,13 +384,6 @@ static unsigned int __blk_recalc_rq_segments(struct request_queue *q, nr_phys_segs = 0; for_each_bio(bio) { bio_for_each_mp_bvec(bv, bio, iter) { - /* - * If SG merging is disabled, each bio vector is - * a segment - */ - if (no_sg_merge) - goto new_segment; - if (prev) { if (seg_size + bv.bv_len > queue_max_segment_size(q))
@@ -421,27 +413,16 @@ 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 90d68760af08..2f9a11ef5bad 100644
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c@@ -128,7 +128,6 @@ 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 3ba37b9e15e9..fa45817a7e62 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c@@ -2829,9 +2829,6 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set, set->map[HCTX_TYPE_POLL].nr_queues) blk_queue_flag_set(QUEUE_FLAG_POLL, q); - 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 4b1be754cc41..ba9481f1bf3c 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 6ebae3ee8f44..2d4cdc1a7bac 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h@@ -588,7 +588,6 @@ 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