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![David Jeffery](/assets/img/avatar_default.png)
When a stacked block device inserts a request into another block device
using blk_insert_cloned_request, the request's nr_phys_segments field gets
recalculated by a call to blk_recalc_rq_segments in
blk_cloned_rq_check_limits. But blk_recalc_rq_segments does not know how to
handle multi-segment discards. For disk types which can handle
multi-segment discards like nvme, this results in discard requests which
claim a single segment when it should report several, triggering a warning
in nvme and causing nvme to fail the discard from the invalid state.
WARNING: CPU: 5 PID: 191 at drivers/nvme/host/core.c:700 nvme_setup_discard+0x170/0x1e0 [nvme_core]
...
nvme_setup_cmd+0x217/0x270 [nvme_core]
nvme_loop_queue_rq+0x51/0x1b0 [nvme_loop]
__blk_mq_try_issue_directly+0xe7/0x1b0
blk_mq_request_issue_directly+0x41/0x70
? blk_account_io_start+0x40/0x50
dm_mq_queue_rq+0x200/0x3e0
blk_mq_dispatch_rq_list+0x10a/0x7d0
? __sbitmap_queue_get+0x25/0x90
? elv_rb_del+0x1f/0x30
? deadline_remove_request+0x55/0xb0
? dd_dispatch_request+0x181/0x210
__blk_mq_do_dispatch_sched+0x144/0x290
? bio_attempt_discard_merge+0x134/0x1f0
__blk_mq_sched_dispatch_requests+0x129/0x180
blk_mq_sched_dispatch_requests+0x30/0x60
__blk_mq_run_hw_queue+0x47/0xe0
__blk_mq_delay_run_hw_queue+0x15b/0x170
blk_mq_sched_insert_requests+0x68/0xe0
blk_mq_flush_plug_list+0xf0/0x170
blk_finish_plug+0x36/0x50
xlog_cil_committed+0x19f/0x290 [xfs]
xlog_cil_process_committed+0x57/0x80 [xfs]
xlog_state_do_callback+0x1e0/0x2a0 [xfs]
xlog_ioend_work+0x2f/0x80 [xfs]
process_one_work+0x1b6/0x350
worker_thread+0x53/0x3e0
? process_one_work+0x350/0x350
kthread+0x11b/0x140
? __kthread_bind_mask+0x60/0x60
ret_from_fork+0x22/0x30
This patch fixes blk_recalc_rq_segments to be aware of devices which can
have multi-segment discards. It calculates the correct discard segment
count by counting the number of bio as each discard bio is considered its
own segment.
Fixes: 1e739730c5
("block: optionally merge discontiguous discard bios into a single request")
Signed-off-by: David Jeffery <djeffery@redhat.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Laurence Oberman <loberman@redhat.com>
Link: https://lore.kernel.org/r/20210211143807.GA115624@redhat
Signed-off-by: Jens Axboe <axboe@kernel.dk>
1149 lines
30 KiB
C
1149 lines
30 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Functions related to segment and merge handling
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/bio.h>
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#include <linux/blkdev.h>
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#include <linux/scatterlist.h>
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#include <trace/events/block.h>
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#include "blk.h"
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#include "blk-rq-qos.h"
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static inline bool bio_will_gap(struct request_queue *q,
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struct request *prev_rq, struct bio *prev, struct bio *next)
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{
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struct bio_vec pb, nb;
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if (!bio_has_data(prev) || !queue_virt_boundary(q))
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return false;
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/*
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* Don't merge if the 1st bio starts with non-zero offset, otherwise it
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* is quite difficult to respect the sg gap limit. We work hard to
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* merge a huge number of small single bios in case of mkfs.
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*/
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if (prev_rq)
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bio_get_first_bvec(prev_rq->bio, &pb);
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else
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bio_get_first_bvec(prev, &pb);
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if (pb.bv_offset & queue_virt_boundary(q))
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return true;
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/*
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* We don't need to worry about the situation that the merged segment
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* ends in unaligned virt boundary:
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*
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* - if 'pb' ends aligned, the merged segment ends aligned
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* - if 'pb' ends unaligned, the next bio must include
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* one single bvec of 'nb', otherwise the 'nb' can't
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* merge with 'pb'
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*/
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bio_get_last_bvec(prev, &pb);
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bio_get_first_bvec(next, &nb);
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if (biovec_phys_mergeable(q, &pb, &nb))
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return false;
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return __bvec_gap_to_prev(q, &pb, nb.bv_offset);
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}
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static inline bool req_gap_back_merge(struct request *req, struct bio *bio)
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{
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return bio_will_gap(req->q, req, req->biotail, bio);
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}
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static inline bool req_gap_front_merge(struct request *req, struct bio *bio)
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{
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return bio_will_gap(req->q, NULL, bio, req->bio);
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}
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static struct bio *blk_bio_discard_split(struct request_queue *q,
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struct bio *bio,
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struct bio_set *bs,
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unsigned *nsegs)
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{
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unsigned int max_discard_sectors, granularity;
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int alignment;
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sector_t tmp;
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unsigned split_sectors;
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*nsegs = 1;
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/* Zero-sector (unknown) and one-sector granularities are the same. */
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granularity = max(q->limits.discard_granularity >> 9, 1U);
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max_discard_sectors = min(q->limits.max_discard_sectors,
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bio_allowed_max_sectors(q));
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max_discard_sectors -= max_discard_sectors % granularity;
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if (unlikely(!max_discard_sectors)) {
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/* XXX: warn */
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return NULL;
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}
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if (bio_sectors(bio) <= max_discard_sectors)
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return NULL;
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split_sectors = max_discard_sectors;
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/*
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* If the next starting sector would be misaligned, stop the discard at
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* the previous aligned sector.
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*/
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alignment = (q->limits.discard_alignment >> 9) % granularity;
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tmp = bio->bi_iter.bi_sector + split_sectors - alignment;
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tmp = sector_div(tmp, granularity);
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if (split_sectors > tmp)
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split_sectors -= tmp;
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return bio_split(bio, split_sectors, GFP_NOIO, bs);
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}
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static struct bio *blk_bio_write_zeroes_split(struct request_queue *q,
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struct bio *bio, struct bio_set *bs, unsigned *nsegs)
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{
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*nsegs = 0;
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if (!q->limits.max_write_zeroes_sectors)
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return NULL;
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if (bio_sectors(bio) <= q->limits.max_write_zeroes_sectors)
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return NULL;
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return bio_split(bio, q->limits.max_write_zeroes_sectors, GFP_NOIO, bs);
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}
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static struct bio *blk_bio_write_same_split(struct request_queue *q,
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struct bio *bio,
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struct bio_set *bs,
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unsigned *nsegs)
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{
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*nsegs = 1;
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if (!q->limits.max_write_same_sectors)
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return NULL;
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if (bio_sectors(bio) <= q->limits.max_write_same_sectors)
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return NULL;
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return bio_split(bio, q->limits.max_write_same_sectors, GFP_NOIO, bs);
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}
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/*
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* Return the maximum number of sectors from the start of a bio that may be
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* submitted as a single request to a block device. If enough sectors remain,
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* align the end to the physical block size. Otherwise align the end to the
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* logical block size. This approach minimizes the number of non-aligned
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* requests that are submitted to a block device if the start of a bio is not
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* aligned to a physical block boundary.
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*/
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static inline unsigned get_max_io_size(struct request_queue *q,
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struct bio *bio)
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{
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unsigned sectors = blk_max_size_offset(q, bio->bi_iter.bi_sector, 0);
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unsigned max_sectors = sectors;
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unsigned pbs = queue_physical_block_size(q) >> SECTOR_SHIFT;
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unsigned lbs = queue_logical_block_size(q) >> SECTOR_SHIFT;
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unsigned start_offset = bio->bi_iter.bi_sector & (pbs - 1);
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max_sectors += start_offset;
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max_sectors &= ~(pbs - 1);
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if (max_sectors > start_offset)
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return max_sectors - start_offset;
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return sectors & ~(lbs - 1);
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}
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static inline unsigned get_max_segment_size(const struct request_queue *q,
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struct page *start_page,
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unsigned long offset)
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{
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unsigned long mask = queue_segment_boundary(q);
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offset = mask & (page_to_phys(start_page) + offset);
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/*
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* overflow may be triggered in case of zero page physical address
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* on 32bit arch, use queue's max segment size when that happens.
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*/
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return min_not_zero(mask - offset + 1,
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(unsigned long)queue_max_segment_size(q));
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}
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/**
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* bvec_split_segs - verify whether or not a bvec should be split in the middle
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* @q: [in] request queue associated with the bio associated with @bv
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* @bv: [in] bvec to examine
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* @nsegs: [in,out] Number of segments in the bio being built. Incremented
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* by the number of segments from @bv that may be appended to that
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* bio without exceeding @max_segs
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* @sectors: [in,out] Number of sectors in the bio being built. Incremented
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* by the number of sectors from @bv that may be appended to that
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* bio without exceeding @max_sectors
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* @max_segs: [in] upper bound for *@nsegs
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* @max_sectors: [in] upper bound for *@sectors
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*
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* When splitting a bio, it can happen that a bvec is encountered that is too
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* big to fit in a single segment and hence that it has to be split in the
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* middle. This function verifies whether or not that should happen. The value
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* %true is returned if and only if appending the entire @bv to a bio with
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* *@nsegs segments and *@sectors sectors would make that bio unacceptable for
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* the block driver.
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*/
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static bool bvec_split_segs(const struct request_queue *q,
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const struct bio_vec *bv, unsigned *nsegs,
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unsigned *sectors, unsigned max_segs,
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unsigned max_sectors)
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{
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unsigned max_len = (min(max_sectors, UINT_MAX >> 9) - *sectors) << 9;
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unsigned len = min(bv->bv_len, max_len);
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unsigned total_len = 0;
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unsigned seg_size = 0;
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while (len && *nsegs < max_segs) {
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seg_size = get_max_segment_size(q, bv->bv_page,
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bv->bv_offset + total_len);
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seg_size = min(seg_size, len);
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(*nsegs)++;
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total_len += seg_size;
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len -= seg_size;
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if ((bv->bv_offset + total_len) & queue_virt_boundary(q))
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break;
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}
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*sectors += total_len >> 9;
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/* tell the caller to split the bvec if it is too big to fit */
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return len > 0 || bv->bv_len > max_len;
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}
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/**
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* blk_bio_segment_split - split a bio in two bios
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* @q: [in] request queue pointer
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* @bio: [in] bio to be split
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* @bs: [in] bio set to allocate the clone from
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* @segs: [out] number of segments in the bio with the first half of the sectors
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*
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* Clone @bio, update the bi_iter of the clone to represent the first sectors
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* of @bio and update @bio->bi_iter to represent the remaining sectors. The
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* following is guaranteed for the cloned bio:
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* - That it has at most get_max_io_size(@q, @bio) sectors.
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* - That it has at most queue_max_segments(@q) segments.
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*
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* Except for discard requests the cloned bio will point at the bi_io_vec of
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* the original bio. It is the responsibility of the caller to ensure that the
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* original bio is not freed before the cloned bio. The caller is also
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* responsible for ensuring that @bs is only destroyed after processing of the
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* split bio has finished.
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*/
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static struct bio *blk_bio_segment_split(struct request_queue *q,
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struct bio *bio,
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struct bio_set *bs,
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unsigned *segs)
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{
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struct bio_vec bv, bvprv, *bvprvp = NULL;
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struct bvec_iter iter;
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unsigned nsegs = 0, sectors = 0;
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const unsigned max_sectors = get_max_io_size(q, bio);
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const unsigned max_segs = queue_max_segments(q);
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bio_for_each_bvec(bv, bio, iter) {
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/*
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* If the queue doesn't support SG gaps and adding this
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* offset would create a gap, disallow it.
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*/
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if (bvprvp && bvec_gap_to_prev(q, bvprvp, bv.bv_offset))
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goto split;
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if (nsegs < max_segs &&
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sectors + (bv.bv_len >> 9) <= max_sectors &&
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bv.bv_offset + bv.bv_len <= PAGE_SIZE) {
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nsegs++;
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sectors += bv.bv_len >> 9;
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} else if (bvec_split_segs(q, &bv, &nsegs, §ors, max_segs,
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max_sectors)) {
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goto split;
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}
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bvprv = bv;
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bvprvp = &bvprv;
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}
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*segs = nsegs;
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return NULL;
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split:
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*segs = nsegs;
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/*
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* Bio splitting may cause subtle trouble such as hang when doing sync
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* iopoll in direct IO routine. Given performance gain of iopoll for
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* big IO can be trival, disable iopoll when split needed.
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*/
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bio->bi_opf &= ~REQ_HIPRI;
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return bio_split(bio, sectors, GFP_NOIO, bs);
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}
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/**
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* __blk_queue_split - split a bio and submit the second half
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* @bio: [in, out] bio to be split
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* @nr_segs: [out] number of segments in the first bio
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*
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* Split a bio into two bios, chain the two bios, submit the second half and
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* store a pointer to the first half in *@bio. If the second bio is still too
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* big it will be split by a recursive call to this function. Since this
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* function may allocate a new bio from q->bio_split, it is the responsibility
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* of the caller to ensure that q->bio_split is only released after processing
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* of the split bio has finished.
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*/
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void __blk_queue_split(struct bio **bio, unsigned int *nr_segs)
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{
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struct request_queue *q = (*bio)->bi_bdev->bd_disk->queue;
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struct bio *split = NULL;
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switch (bio_op(*bio)) {
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case REQ_OP_DISCARD:
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case REQ_OP_SECURE_ERASE:
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split = blk_bio_discard_split(q, *bio, &q->bio_split, nr_segs);
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break;
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case REQ_OP_WRITE_ZEROES:
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split = blk_bio_write_zeroes_split(q, *bio, &q->bio_split,
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nr_segs);
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break;
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case REQ_OP_WRITE_SAME:
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split = blk_bio_write_same_split(q, *bio, &q->bio_split,
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nr_segs);
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break;
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default:
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/*
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* All drivers must accept single-segments bios that are <=
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* PAGE_SIZE. This is a quick and dirty check that relies on
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* the fact that bi_io_vec[0] is always valid if a bio has data.
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* The check might lead to occasional false negatives when bios
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* are cloned, but compared to the performance impact of cloned
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* bios themselves the loop below doesn't matter anyway.
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*/
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if (!q->limits.chunk_sectors &&
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(*bio)->bi_vcnt == 1 &&
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((*bio)->bi_io_vec[0].bv_len +
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(*bio)->bi_io_vec[0].bv_offset) <= PAGE_SIZE) {
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*nr_segs = 1;
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break;
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}
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split = blk_bio_segment_split(q, *bio, &q->bio_split, nr_segs);
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break;
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}
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if (split) {
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/* there isn't chance to merge the splitted bio */
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split->bi_opf |= REQ_NOMERGE;
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bio_chain(split, *bio);
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trace_block_split(split, (*bio)->bi_iter.bi_sector);
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submit_bio_noacct(*bio);
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*bio = split;
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}
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}
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/**
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* blk_queue_split - split a bio and submit the second half
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* @bio: [in, out] bio to be split
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*
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* Split a bio into two bios, chains the two bios, submit the second half and
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* store a pointer to the first half in *@bio. Since this function may allocate
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* a new bio from q->bio_split, it is the responsibility of the caller to ensure
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* that q->bio_split is only released after processing of the split bio has
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* finished.
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*/
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void blk_queue_split(struct bio **bio)
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{
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unsigned int nr_segs;
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__blk_queue_split(bio, &nr_segs);
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}
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EXPORT_SYMBOL(blk_queue_split);
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unsigned int blk_recalc_rq_segments(struct request *rq)
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{
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unsigned int nr_phys_segs = 0;
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unsigned int nr_sectors = 0;
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struct req_iterator iter;
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struct bio_vec bv;
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|
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if (!rq->bio)
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return 0;
|
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|
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switch (bio_op(rq->bio)) {
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case REQ_OP_DISCARD:
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case REQ_OP_SECURE_ERASE:
|
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if (queue_max_discard_segments(rq->q) > 1) {
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struct bio *bio = rq->bio;
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|
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for_each_bio(bio)
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nr_phys_segs++;
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return nr_phys_segs;
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}
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return 1;
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case REQ_OP_WRITE_ZEROES:
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return 0;
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case REQ_OP_WRITE_SAME:
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return 1;
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}
|
|
|
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rq_for_each_bvec(bv, rq, iter)
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bvec_split_segs(rq->q, &bv, &nr_phys_segs, &nr_sectors,
|
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UINT_MAX, UINT_MAX);
|
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return nr_phys_segs;
|
|
}
|
|
|
|
static inline struct scatterlist *blk_next_sg(struct scatterlist **sg,
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|
struct scatterlist *sglist)
|
|
{
|
|
if (!*sg)
|
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return sglist;
|
|
|
|
/*
|
|
* If the driver previously mapped a shorter list, we could see a
|
|
* termination bit prematurely unless it fully inits the sg table
|
|
* on each mapping. We KNOW that there must be more entries here
|
|
* or the driver would be buggy, so force clear the termination bit
|
|
* to avoid doing a full sg_init_table() in drivers for each command.
|
|
*/
|
|
sg_unmark_end(*sg);
|
|
return sg_next(*sg);
|
|
}
|
|
|
|
static unsigned blk_bvec_map_sg(struct request_queue *q,
|
|
struct bio_vec *bvec, struct scatterlist *sglist,
|
|
struct scatterlist **sg)
|
|
{
|
|
unsigned nbytes = bvec->bv_len;
|
|
unsigned nsegs = 0, total = 0;
|
|
|
|
while (nbytes > 0) {
|
|
unsigned offset = bvec->bv_offset + total;
|
|
unsigned len = min(get_max_segment_size(q, bvec->bv_page,
|
|
offset), nbytes);
|
|
struct page *page = bvec->bv_page;
|
|
|
|
/*
|
|
* Unfortunately a fair number of drivers barf on scatterlists
|
|
* that have an offset larger than PAGE_SIZE, despite other
|
|
* subsystems dealing with that invariant just fine. For now
|
|
* stick to the legacy format where we never present those from
|
|
* the block layer, but the code below should be removed once
|
|
* these offenders (mostly MMC/SD drivers) are fixed.
|
|
*/
|
|
page += (offset >> PAGE_SHIFT);
|
|
offset &= ~PAGE_MASK;
|
|
|
|
*sg = blk_next_sg(sg, sglist);
|
|
sg_set_page(*sg, page, len, offset);
|
|
|
|
total += len;
|
|
nbytes -= len;
|
|
nsegs++;
|
|
}
|
|
|
|
return nsegs;
|
|
}
|
|
|
|
static inline int __blk_bvec_map_sg(struct bio_vec bv,
|
|
struct scatterlist *sglist, struct scatterlist **sg)
|
|
{
|
|
*sg = blk_next_sg(sg, sglist);
|
|
sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset);
|
|
return 1;
|
|
}
|
|
|
|
/* only try to merge bvecs into one sg if they are from two bios */
|
|
static inline bool
|
|
__blk_segment_map_sg_merge(struct request_queue *q, struct bio_vec *bvec,
|
|
struct bio_vec *bvprv, struct scatterlist **sg)
|
|
{
|
|
|
|
int nbytes = bvec->bv_len;
|
|
|
|
if (!*sg)
|
|
return false;
|
|
|
|
if ((*sg)->length + nbytes > queue_max_segment_size(q))
|
|
return false;
|
|
|
|
if (!biovec_phys_mergeable(q, bvprv, bvec))
|
|
return false;
|
|
|
|
(*sg)->length += nbytes;
|
|
|
|
return true;
|
|
}
|
|
|
|
static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio,
|
|
struct scatterlist *sglist,
|
|
struct scatterlist **sg)
|
|
{
|
|
struct bio_vec bvec, bvprv = { NULL };
|
|
struct bvec_iter iter;
|
|
int nsegs = 0;
|
|
bool new_bio = false;
|
|
|
|
for_each_bio(bio) {
|
|
bio_for_each_bvec(bvec, bio, iter) {
|
|
/*
|
|
* Only try to merge bvecs from two bios given we
|
|
* have done bio internal merge when adding pages
|
|
* to bio
|
|
*/
|
|
if (new_bio &&
|
|
__blk_segment_map_sg_merge(q, &bvec, &bvprv, sg))
|
|
goto next_bvec;
|
|
|
|
if (bvec.bv_offset + bvec.bv_len <= PAGE_SIZE)
|
|
nsegs += __blk_bvec_map_sg(bvec, sglist, sg);
|
|
else
|
|
nsegs += blk_bvec_map_sg(q, &bvec, sglist, sg);
|
|
next_bvec:
|
|
new_bio = false;
|
|
}
|
|
if (likely(bio->bi_iter.bi_size)) {
|
|
bvprv = bvec;
|
|
new_bio = true;
|
|
}
|
|
}
|
|
|
|
return nsegs;
|
|
}
|
|
|
|
/*
|
|
* map a request to scatterlist, return number of sg entries setup. Caller
|
|
* must make sure sg can hold rq->nr_phys_segments entries
|
|
*/
|
|
int __blk_rq_map_sg(struct request_queue *q, struct request *rq,
|
|
struct scatterlist *sglist, struct scatterlist **last_sg)
|
|
{
|
|
int nsegs = 0;
|
|
|
|
if (rq->rq_flags & RQF_SPECIAL_PAYLOAD)
|
|
nsegs = __blk_bvec_map_sg(rq->special_vec, sglist, last_sg);
|
|
else if (rq->bio && bio_op(rq->bio) == REQ_OP_WRITE_SAME)
|
|
nsegs = __blk_bvec_map_sg(bio_iovec(rq->bio), sglist, last_sg);
|
|
else if (rq->bio)
|
|
nsegs = __blk_bios_map_sg(q, rq->bio, sglist, last_sg);
|
|
|
|
if (*last_sg)
|
|
sg_mark_end(*last_sg);
|
|
|
|
/*
|
|
* Something must have been wrong if the figured number of
|
|
* segment is bigger than number of req's physical segments
|
|
*/
|
|
WARN_ON(nsegs > blk_rq_nr_phys_segments(rq));
|
|
|
|
return nsegs;
|
|
}
|
|
EXPORT_SYMBOL(__blk_rq_map_sg);
|
|
|
|
static inline unsigned int blk_rq_get_max_segments(struct request *rq)
|
|
{
|
|
if (req_op(rq) == REQ_OP_DISCARD)
|
|
return queue_max_discard_segments(rq->q);
|
|
return queue_max_segments(rq->q);
|
|
}
|
|
|
|
static inline int ll_new_hw_segment(struct request *req, struct bio *bio,
|
|
unsigned int nr_phys_segs)
|
|
{
|
|
if (req->nr_phys_segments + nr_phys_segs > blk_rq_get_max_segments(req))
|
|
goto no_merge;
|
|
|
|
if (blk_integrity_merge_bio(req->q, req, bio) == false)
|
|
goto no_merge;
|
|
|
|
/*
|
|
* This will form the start of a new hw segment. Bump both
|
|
* counters.
|
|
*/
|
|
req->nr_phys_segments += nr_phys_segs;
|
|
return 1;
|
|
|
|
no_merge:
|
|
req_set_nomerge(req->q, req);
|
|
return 0;
|
|
}
|
|
|
|
int ll_back_merge_fn(struct request *req, struct bio *bio, unsigned int nr_segs)
|
|
{
|
|
if (req_gap_back_merge(req, bio))
|
|
return 0;
|
|
if (blk_integrity_rq(req) &&
|
|
integrity_req_gap_back_merge(req, bio))
|
|
return 0;
|
|
if (!bio_crypt_ctx_back_mergeable(req, bio))
|
|
return 0;
|
|
if (blk_rq_sectors(req) + bio_sectors(bio) >
|
|
blk_rq_get_max_sectors(req, blk_rq_pos(req))) {
|
|
req_set_nomerge(req->q, req);
|
|
return 0;
|
|
}
|
|
|
|
return ll_new_hw_segment(req, bio, nr_segs);
|
|
}
|
|
|
|
static int ll_front_merge_fn(struct request *req, struct bio *bio,
|
|
unsigned int nr_segs)
|
|
{
|
|
if (req_gap_front_merge(req, bio))
|
|
return 0;
|
|
if (blk_integrity_rq(req) &&
|
|
integrity_req_gap_front_merge(req, bio))
|
|
return 0;
|
|
if (!bio_crypt_ctx_front_mergeable(req, bio))
|
|
return 0;
|
|
if (blk_rq_sectors(req) + bio_sectors(bio) >
|
|
blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) {
|
|
req_set_nomerge(req->q, req);
|
|
return 0;
|
|
}
|
|
|
|
return ll_new_hw_segment(req, bio, nr_segs);
|
|
}
|
|
|
|
static bool req_attempt_discard_merge(struct request_queue *q, struct request *req,
|
|
struct request *next)
|
|
{
|
|
unsigned short segments = blk_rq_nr_discard_segments(req);
|
|
|
|
if (segments >= queue_max_discard_segments(q))
|
|
goto no_merge;
|
|
if (blk_rq_sectors(req) + bio_sectors(next->bio) >
|
|
blk_rq_get_max_sectors(req, blk_rq_pos(req)))
|
|
goto no_merge;
|
|
|
|
req->nr_phys_segments = segments + blk_rq_nr_discard_segments(next);
|
|
return true;
|
|
no_merge:
|
|
req_set_nomerge(q, req);
|
|
return false;
|
|
}
|
|
|
|
static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
|
|
struct request *next)
|
|
{
|
|
int total_phys_segments;
|
|
|
|
if (req_gap_back_merge(req, next->bio))
|
|
return 0;
|
|
|
|
/*
|
|
* Will it become too large?
|
|
*/
|
|
if ((blk_rq_sectors(req) + blk_rq_sectors(next)) >
|
|
blk_rq_get_max_sectors(req, blk_rq_pos(req)))
|
|
return 0;
|
|
|
|
total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
|
|
if (total_phys_segments > blk_rq_get_max_segments(req))
|
|
return 0;
|
|
|
|
if (blk_integrity_merge_rq(q, req, next) == false)
|
|
return 0;
|
|
|
|
if (!bio_crypt_ctx_merge_rq(req, next))
|
|
return 0;
|
|
|
|
/* Merge is OK... */
|
|
req->nr_phys_segments = total_phys_segments;
|
|
return 1;
|
|
}
|
|
|
|
/**
|
|
* blk_rq_set_mixed_merge - mark a request as mixed merge
|
|
* @rq: request to mark as mixed merge
|
|
*
|
|
* Description:
|
|
* @rq is about to be mixed merged. Make sure the attributes
|
|
* which can be mixed are set in each bio and mark @rq as mixed
|
|
* merged.
|
|
*/
|
|
void blk_rq_set_mixed_merge(struct request *rq)
|
|
{
|
|
unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
|
|
struct bio *bio;
|
|
|
|
if (rq->rq_flags & RQF_MIXED_MERGE)
|
|
return;
|
|
|
|
/*
|
|
* @rq will no longer represent mixable attributes for all the
|
|
* contained bios. It will just track those of the first one.
|
|
* Distributes the attributs to each bio.
|
|
*/
|
|
for (bio = rq->bio; bio; bio = bio->bi_next) {
|
|
WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) &&
|
|
(bio->bi_opf & REQ_FAILFAST_MASK) != ff);
|
|
bio->bi_opf |= ff;
|
|
}
|
|
rq->rq_flags |= RQF_MIXED_MERGE;
|
|
}
|
|
|
|
static void blk_account_io_merge_request(struct request *req)
|
|
{
|
|
if (blk_do_io_stat(req)) {
|
|
part_stat_lock();
|
|
part_stat_inc(req->part, merges[op_stat_group(req_op(req))]);
|
|
part_stat_unlock();
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Two cases of handling DISCARD merge:
|
|
* If max_discard_segments > 1, the driver takes every bio
|
|
* as a range and send them to controller together. The ranges
|
|
* needn't to be contiguous.
|
|
* Otherwise, the bios/requests will be handled as same as
|
|
* others which should be contiguous.
|
|
*/
|
|
static inline bool blk_discard_mergable(struct request *req)
|
|
{
|
|
if (req_op(req) == REQ_OP_DISCARD &&
|
|
queue_max_discard_segments(req->q) > 1)
|
|
return true;
|
|
return false;
|
|
}
|
|
|
|
static enum elv_merge blk_try_req_merge(struct request *req,
|
|
struct request *next)
|
|
{
|
|
if (blk_discard_mergable(req))
|
|
return ELEVATOR_DISCARD_MERGE;
|
|
else if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next))
|
|
return ELEVATOR_BACK_MERGE;
|
|
|
|
return ELEVATOR_NO_MERGE;
|
|
}
|
|
|
|
/*
|
|
* For non-mq, this has to be called with the request spinlock acquired.
|
|
* For mq with scheduling, the appropriate queue wide lock should be held.
|
|
*/
|
|
static struct request *attempt_merge(struct request_queue *q,
|
|
struct request *req, struct request *next)
|
|
{
|
|
if (!rq_mergeable(req) || !rq_mergeable(next))
|
|
return NULL;
|
|
|
|
if (req_op(req) != req_op(next))
|
|
return NULL;
|
|
|
|
if (rq_data_dir(req) != rq_data_dir(next)
|
|
|| req->rq_disk != next->rq_disk)
|
|
return NULL;
|
|
|
|
if (req_op(req) == REQ_OP_WRITE_SAME &&
|
|
!blk_write_same_mergeable(req->bio, next->bio))
|
|
return NULL;
|
|
|
|
/*
|
|
* Don't allow merge of different write hints, or for a hint with
|
|
* non-hint IO.
|
|
*/
|
|
if (req->write_hint != next->write_hint)
|
|
return NULL;
|
|
|
|
if (req->ioprio != next->ioprio)
|
|
return NULL;
|
|
|
|
/*
|
|
* If we are allowed to merge, then append bio list
|
|
* from next to rq and release next. merge_requests_fn
|
|
* will have updated segment counts, update sector
|
|
* counts here. Handle DISCARDs separately, as they
|
|
* have separate settings.
|
|
*/
|
|
|
|
switch (blk_try_req_merge(req, next)) {
|
|
case ELEVATOR_DISCARD_MERGE:
|
|
if (!req_attempt_discard_merge(q, req, next))
|
|
return NULL;
|
|
break;
|
|
case ELEVATOR_BACK_MERGE:
|
|
if (!ll_merge_requests_fn(q, req, next))
|
|
return NULL;
|
|
break;
|
|
default:
|
|
return NULL;
|
|
}
|
|
|
|
/*
|
|
* If failfast settings disagree or any of the two is already
|
|
* a mixed merge, mark both as mixed before proceeding. This
|
|
* makes sure that all involved bios have mixable attributes
|
|
* set properly.
|
|
*/
|
|
if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) ||
|
|
(req->cmd_flags & REQ_FAILFAST_MASK) !=
|
|
(next->cmd_flags & REQ_FAILFAST_MASK)) {
|
|
blk_rq_set_mixed_merge(req);
|
|
blk_rq_set_mixed_merge(next);
|
|
}
|
|
|
|
/*
|
|
* At this point we have either done a back merge or front merge. We
|
|
* need the smaller start_time_ns of the merged requests to be the
|
|
* current request for accounting purposes.
|
|
*/
|
|
if (next->start_time_ns < req->start_time_ns)
|
|
req->start_time_ns = next->start_time_ns;
|
|
|
|
req->biotail->bi_next = next->bio;
|
|
req->biotail = next->biotail;
|
|
|
|
req->__data_len += blk_rq_bytes(next);
|
|
|
|
if (!blk_discard_mergable(req))
|
|
elv_merge_requests(q, req, next);
|
|
|
|
/*
|
|
* 'next' is going away, so update stats accordingly
|
|
*/
|
|
blk_account_io_merge_request(next);
|
|
|
|
trace_block_rq_merge(next);
|
|
|
|
/*
|
|
* ownership of bio passed from next to req, return 'next' for
|
|
* the caller to free
|
|
*/
|
|
next->bio = NULL;
|
|
return next;
|
|
}
|
|
|
|
static struct request *attempt_back_merge(struct request_queue *q,
|
|
struct request *rq)
|
|
{
|
|
struct request *next = elv_latter_request(q, rq);
|
|
|
|
if (next)
|
|
return attempt_merge(q, rq, next);
|
|
|
|
return NULL;
|
|
}
|
|
|
|
static struct request *attempt_front_merge(struct request_queue *q,
|
|
struct request *rq)
|
|
{
|
|
struct request *prev = elv_former_request(q, rq);
|
|
|
|
if (prev)
|
|
return attempt_merge(q, prev, rq);
|
|
|
|
return NULL;
|
|
}
|
|
|
|
int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
|
|
struct request *next)
|
|
{
|
|
struct request *free;
|
|
|
|
free = attempt_merge(q, rq, next);
|
|
if (free) {
|
|
blk_put_request(free);
|
|
return 1;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
|
|
{
|
|
if (!rq_mergeable(rq) || !bio_mergeable(bio))
|
|
return false;
|
|
|
|
if (req_op(rq) != bio_op(bio))
|
|
return false;
|
|
|
|
/* different data direction or already started, don't merge */
|
|
if (bio_data_dir(bio) != rq_data_dir(rq))
|
|
return false;
|
|
|
|
/* must be same device */
|
|
if (rq->rq_disk != bio->bi_bdev->bd_disk)
|
|
return false;
|
|
|
|
/* only merge integrity protected bio into ditto rq */
|
|
if (blk_integrity_merge_bio(rq->q, rq, bio) == false)
|
|
return false;
|
|
|
|
/* Only merge if the crypt contexts are compatible */
|
|
if (!bio_crypt_rq_ctx_compatible(rq, bio))
|
|
return false;
|
|
|
|
/* must be using the same buffer */
|
|
if (req_op(rq) == REQ_OP_WRITE_SAME &&
|
|
!blk_write_same_mergeable(rq->bio, bio))
|
|
return false;
|
|
|
|
/*
|
|
* Don't allow merge of different write hints, or for a hint with
|
|
* non-hint IO.
|
|
*/
|
|
if (rq->write_hint != bio->bi_write_hint)
|
|
return false;
|
|
|
|
if (rq->ioprio != bio_prio(bio))
|
|
return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
enum elv_merge blk_try_merge(struct request *rq, struct bio *bio)
|
|
{
|
|
if (blk_discard_mergable(rq))
|
|
return ELEVATOR_DISCARD_MERGE;
|
|
else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
|
|
return ELEVATOR_BACK_MERGE;
|
|
else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector)
|
|
return ELEVATOR_FRONT_MERGE;
|
|
return ELEVATOR_NO_MERGE;
|
|
}
|
|
|
|
static void blk_account_io_merge_bio(struct request *req)
|
|
{
|
|
if (!blk_do_io_stat(req))
|
|
return;
|
|
|
|
part_stat_lock();
|
|
part_stat_inc(req->part, merges[op_stat_group(req_op(req))]);
|
|
part_stat_unlock();
|
|
}
|
|
|
|
enum bio_merge_status {
|
|
BIO_MERGE_OK,
|
|
BIO_MERGE_NONE,
|
|
BIO_MERGE_FAILED,
|
|
};
|
|
|
|
static enum bio_merge_status bio_attempt_back_merge(struct request *req,
|
|
struct bio *bio, unsigned int nr_segs)
|
|
{
|
|
const int ff = bio->bi_opf & REQ_FAILFAST_MASK;
|
|
|
|
if (!ll_back_merge_fn(req, bio, nr_segs))
|
|
return BIO_MERGE_FAILED;
|
|
|
|
trace_block_bio_backmerge(bio);
|
|
rq_qos_merge(req->q, req, bio);
|
|
|
|
if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
|
|
blk_rq_set_mixed_merge(req);
|
|
|
|
req->biotail->bi_next = bio;
|
|
req->biotail = bio;
|
|
req->__data_len += bio->bi_iter.bi_size;
|
|
|
|
bio_crypt_free_ctx(bio);
|
|
|
|
blk_account_io_merge_bio(req);
|
|
return BIO_MERGE_OK;
|
|
}
|
|
|
|
static enum bio_merge_status bio_attempt_front_merge(struct request *req,
|
|
struct bio *bio, unsigned int nr_segs)
|
|
{
|
|
const int ff = bio->bi_opf & REQ_FAILFAST_MASK;
|
|
|
|
if (!ll_front_merge_fn(req, bio, nr_segs))
|
|
return BIO_MERGE_FAILED;
|
|
|
|
trace_block_bio_frontmerge(bio);
|
|
rq_qos_merge(req->q, req, bio);
|
|
|
|
if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
|
|
blk_rq_set_mixed_merge(req);
|
|
|
|
bio->bi_next = req->bio;
|
|
req->bio = bio;
|
|
|
|
req->__sector = bio->bi_iter.bi_sector;
|
|
req->__data_len += bio->bi_iter.bi_size;
|
|
|
|
bio_crypt_do_front_merge(req, bio);
|
|
|
|
blk_account_io_merge_bio(req);
|
|
return BIO_MERGE_OK;
|
|
}
|
|
|
|
static enum bio_merge_status bio_attempt_discard_merge(struct request_queue *q,
|
|
struct request *req, struct bio *bio)
|
|
{
|
|
unsigned short segments = blk_rq_nr_discard_segments(req);
|
|
|
|
if (segments >= queue_max_discard_segments(q))
|
|
goto no_merge;
|
|
if (blk_rq_sectors(req) + bio_sectors(bio) >
|
|
blk_rq_get_max_sectors(req, blk_rq_pos(req)))
|
|
goto no_merge;
|
|
|
|
rq_qos_merge(q, req, bio);
|
|
|
|
req->biotail->bi_next = bio;
|
|
req->biotail = bio;
|
|
req->__data_len += bio->bi_iter.bi_size;
|
|
req->nr_phys_segments = segments + 1;
|
|
|
|
blk_account_io_merge_bio(req);
|
|
return BIO_MERGE_OK;
|
|
no_merge:
|
|
req_set_nomerge(q, req);
|
|
return BIO_MERGE_FAILED;
|
|
}
|
|
|
|
static enum bio_merge_status blk_attempt_bio_merge(struct request_queue *q,
|
|
struct request *rq,
|
|
struct bio *bio,
|
|
unsigned int nr_segs,
|
|
bool sched_allow_merge)
|
|
{
|
|
if (!blk_rq_merge_ok(rq, bio))
|
|
return BIO_MERGE_NONE;
|
|
|
|
switch (blk_try_merge(rq, bio)) {
|
|
case ELEVATOR_BACK_MERGE:
|
|
if (!sched_allow_merge || blk_mq_sched_allow_merge(q, rq, bio))
|
|
return bio_attempt_back_merge(rq, bio, nr_segs);
|
|
break;
|
|
case ELEVATOR_FRONT_MERGE:
|
|
if (!sched_allow_merge || blk_mq_sched_allow_merge(q, rq, bio))
|
|
return bio_attempt_front_merge(rq, bio, nr_segs);
|
|
break;
|
|
case ELEVATOR_DISCARD_MERGE:
|
|
return bio_attempt_discard_merge(q, rq, bio);
|
|
default:
|
|
return BIO_MERGE_NONE;
|
|
}
|
|
|
|
return BIO_MERGE_FAILED;
|
|
}
|
|
|
|
/**
|
|
* blk_attempt_plug_merge - try to merge with %current's plugged list
|
|
* @q: request_queue new bio is being queued at
|
|
* @bio: new bio being queued
|
|
* @nr_segs: number of segments in @bio
|
|
* @same_queue_rq: pointer to &struct request that gets filled in when
|
|
* another request associated with @q is found on the plug list
|
|
* (optional, may be %NULL)
|
|
*
|
|
* Determine whether @bio being queued on @q can be merged with a request
|
|
* on %current's plugged list. Returns %true if merge was successful,
|
|
* otherwise %false.
|
|
*
|
|
* Plugging coalesces IOs from the same issuer for the same purpose without
|
|
* going through @q->queue_lock. As such it's more of an issuing mechanism
|
|
* than scheduling, and the request, while may have elvpriv data, is not
|
|
* added on the elevator at this point. In addition, we don't have
|
|
* reliable access to the elevator outside queue lock. Only check basic
|
|
* merging parameters without querying the elevator.
|
|
*
|
|
* Caller must ensure !blk_queue_nomerges(q) beforehand.
|
|
*/
|
|
bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
|
|
unsigned int nr_segs, struct request **same_queue_rq)
|
|
{
|
|
struct blk_plug *plug;
|
|
struct request *rq;
|
|
struct list_head *plug_list;
|
|
|
|
plug = blk_mq_plug(q, bio);
|
|
if (!plug)
|
|
return false;
|
|
|
|
plug_list = &plug->mq_list;
|
|
|
|
list_for_each_entry_reverse(rq, plug_list, queuelist) {
|
|
if (rq->q == q && same_queue_rq) {
|
|
/*
|
|
* Only blk-mq multiple hardware queues case checks the
|
|
* rq in the same queue, there should be only one such
|
|
* rq in a queue
|
|
**/
|
|
*same_queue_rq = rq;
|
|
}
|
|
|
|
if (rq->q != q)
|
|
continue;
|
|
|
|
if (blk_attempt_bio_merge(q, rq, bio, nr_segs, false) ==
|
|
BIO_MERGE_OK)
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
/*
|
|
* Iterate list of requests and see if we can merge this bio with any
|
|
* of them.
|
|
*/
|
|
bool blk_bio_list_merge(struct request_queue *q, struct list_head *list,
|
|
struct bio *bio, unsigned int nr_segs)
|
|
{
|
|
struct request *rq;
|
|
int checked = 8;
|
|
|
|
list_for_each_entry_reverse(rq, list, queuelist) {
|
|
if (!checked--)
|
|
break;
|
|
|
|
switch (blk_attempt_bio_merge(q, rq, bio, nr_segs, true)) {
|
|
case BIO_MERGE_NONE:
|
|
continue;
|
|
case BIO_MERGE_OK:
|
|
return true;
|
|
case BIO_MERGE_FAILED:
|
|
return false;
|
|
}
|
|
|
|
}
|
|
|
|
return false;
|
|
}
|
|
EXPORT_SYMBOL_GPL(blk_bio_list_merge);
|
|
|
|
bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
|
|
unsigned int nr_segs, struct request **merged_request)
|
|
{
|
|
struct request *rq;
|
|
|
|
switch (elv_merge(q, &rq, bio)) {
|
|
case ELEVATOR_BACK_MERGE:
|
|
if (!blk_mq_sched_allow_merge(q, rq, bio))
|
|
return false;
|
|
if (bio_attempt_back_merge(rq, bio, nr_segs) != BIO_MERGE_OK)
|
|
return false;
|
|
*merged_request = attempt_back_merge(q, rq);
|
|
if (!*merged_request)
|
|
elv_merged_request(q, rq, ELEVATOR_BACK_MERGE);
|
|
return true;
|
|
case ELEVATOR_FRONT_MERGE:
|
|
if (!blk_mq_sched_allow_merge(q, rq, bio))
|
|
return false;
|
|
if (bio_attempt_front_merge(rq, bio, nr_segs) != BIO_MERGE_OK)
|
|
return false;
|
|
*merged_request = attempt_front_merge(q, rq);
|
|
if (!*merged_request)
|
|
elv_merged_request(q, rq, ELEVATOR_FRONT_MERGE);
|
|
return true;
|
|
case ELEVATOR_DISCARD_MERGE:
|
|
return bio_attempt_discard_merge(q, rq, bio) == BIO_MERGE_OK;
|
|
default:
|
|
return false;
|
|
}
|
|
}
|
|
EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge);
|