Revision 6bc9b56433b76e40d11099338d27fbc5cd2935ca authored by Naoya Horiguchi on 24 August 2018, 00:00:38 UTC, committed by Linus Torvalds on 24 August 2018, 01:48:43 UTC
Patch series "mm: soft-offline: fix race against page allocation". Xishi recently reported the issue about race on reusing the target pages of soft offlining. Discussion and analysis showed that we need make sure that setting PG_hwpoison should be done in the right place under zone->lock for soft offline. 1/2 handles free hugepage's case, and 2/2 hanldes free buddy page's case. This patch (of 2): There's a race condition between soft offline and hugetlb_fault which causes unexpected process killing and/or hugetlb allocation failure. The process killing is caused by the following flow: CPU 0 CPU 1 CPU 2 soft offline get_any_page // find the hugetlb is free mmap a hugetlb file page fault ... hugetlb_fault hugetlb_no_page alloc_huge_page // succeed soft_offline_free_page // set hwpoison flag mmap the hugetlb file page fault ... hugetlb_fault hugetlb_no_page find_lock_page return VM_FAULT_HWPOISON mm_fault_error do_sigbus // kill the process The hugetlb allocation failure comes from the following flow: CPU 0 CPU 1 mmap a hugetlb file // reserve all free page but don't fault-in soft offline get_any_page // find the hugetlb is free soft_offline_free_page // set hwpoison flag dissolve_free_huge_page // fail because all free hugepages are reserved page fault ... hugetlb_fault hugetlb_no_page alloc_huge_page ... dequeue_huge_page_node_exact // ignore hwpoisoned hugepage // and finally fail due to no-mem The root cause of this is that current soft-offline code is written based on an assumption that PageHWPoison flag should be set at first to avoid accessing the corrupted data. This makes sense for memory_failure() or hard offline, but does not for soft offline because soft offline is about corrected (not uncorrected) error and is safe from data lost. This patch changes soft offline semantics where it sets PageHWPoison flag only after containment of the error page completes successfully. Link: http://lkml.kernel.org/r/1531452366-11661-2-git-send-email-n-horiguchi@ah.jp.nec.com Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Reported-by: Xishi Qiu <xishi.qiuxishi@alibaba-inc.com> Suggested-by: Xishi Qiu <xishi.qiuxishi@alibaba-inc.com> Tested-by: Mike Kravetz <mike.kravetz@oracle.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: <zy.zhengyi@alibaba-inc.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 30aba66
blk-merge.c
// SPDX-License-Identifier: GPL-2.0
/*
* Functions related to segment and merge handling
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/scatterlist.h>
#include <trace/events/block.h>
#include "blk.h"
static struct bio *blk_bio_discard_split(struct request_queue *q,
struct bio *bio,
struct bio_set *bs,
unsigned *nsegs)
{
unsigned int max_discard_sectors, granularity;
int alignment;
sector_t tmp;
unsigned split_sectors;
*nsegs = 1;
/* Zero-sector (unknown) and one-sector granularities are the same. */
granularity = max(q->limits.discard_granularity >> 9, 1U);
max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9);
max_discard_sectors -= max_discard_sectors % granularity;
if (unlikely(!max_discard_sectors)) {
/* XXX: warn */
return NULL;
}
if (bio_sectors(bio) <= max_discard_sectors)
return NULL;
split_sectors = max_discard_sectors;
/*
* If the next starting sector would be misaligned, stop the discard at
* the previous aligned sector.
*/
alignment = (q->limits.discard_alignment >> 9) % granularity;
tmp = bio->bi_iter.bi_sector + split_sectors - alignment;
tmp = sector_div(tmp, granularity);
if (split_sectors > tmp)
split_sectors -= tmp;
return bio_split(bio, split_sectors, GFP_NOIO, bs);
}
static struct bio *blk_bio_write_zeroes_split(struct request_queue *q,
struct bio *bio, struct bio_set *bs, unsigned *nsegs)
{
*nsegs = 1;
if (!q->limits.max_write_zeroes_sectors)
return NULL;
if (bio_sectors(bio) <= q->limits.max_write_zeroes_sectors)
return NULL;
return bio_split(bio, q->limits.max_write_zeroes_sectors, GFP_NOIO, bs);
}
static struct bio *blk_bio_write_same_split(struct request_queue *q,
struct bio *bio,
struct bio_set *bs,
unsigned *nsegs)
{
*nsegs = 1;
if (!q->limits.max_write_same_sectors)
return NULL;
if (bio_sectors(bio) <= q->limits.max_write_same_sectors)
return NULL;
return bio_split(bio, q->limits.max_write_same_sectors, GFP_NOIO, bs);
}
static inline unsigned get_max_io_size(struct request_queue *q,
struct bio *bio)
{
unsigned sectors = blk_max_size_offset(q, bio->bi_iter.bi_sector);
unsigned mask = queue_logical_block_size(q) - 1;
/* aligned to logical block size */
sectors &= ~(mask >> 9);
return sectors;
}
static struct bio *blk_bio_segment_split(struct request_queue *q,
struct bio *bio,
struct bio_set *bs,
unsigned *segs)
{
struct bio_vec bv, bvprv, *bvprvp = NULL;
struct bvec_iter iter;
unsigned seg_size = 0, nsegs = 0, sectors = 0;
unsigned front_seg_size = bio->bi_seg_front_size;
bool do_split = true;
struct bio *new = NULL;
const unsigned max_sectors = get_max_io_size(q, bio);
bio_for_each_segment(bv, bio, iter) {
/*
* If the queue doesn't support SG gaps and adding this
* offset would create a gap, disallow it.
*/
if (bvprvp && bvec_gap_to_prev(q, bvprvp, bv.bv_offset))
goto split;
if (sectors + (bv.bv_len >> 9) > max_sectors) {
/*
* Consider this a new segment if we're splitting in
* the middle of this vector.
*/
if (nsegs < queue_max_segments(q) &&
sectors < max_sectors) {
nsegs++;
sectors = max_sectors;
}
goto split;
}
if (bvprvp && blk_queue_cluster(q)) {
if (seg_size + bv.bv_len > queue_max_segment_size(q))
goto new_segment;
if (!BIOVEC_PHYS_MERGEABLE(bvprvp, &bv))
goto new_segment;
if (!BIOVEC_SEG_BOUNDARY(q, bvprvp, &bv))
goto new_segment;
seg_size += bv.bv_len;
bvprv = bv;
bvprvp = &bvprv;
sectors += bv.bv_len >> 9;
continue;
}
new_segment:
if (nsegs == queue_max_segments(q))
goto split;
if (nsegs == 1 && seg_size > front_seg_size)
front_seg_size = seg_size;
nsegs++;
bvprv = bv;
bvprvp = &bvprv;
seg_size = bv.bv_len;
sectors += bv.bv_len >> 9;
}
do_split = false;
split:
*segs = nsegs;
if (do_split) {
new = bio_split(bio, sectors, GFP_NOIO, bs);
if (new)
bio = new;
}
if (nsegs == 1 && seg_size > front_seg_size)
front_seg_size = seg_size;
bio->bi_seg_front_size = front_seg_size;
if (seg_size > bio->bi_seg_back_size)
bio->bi_seg_back_size = seg_size;
return do_split ? new : NULL;
}
void blk_queue_split(struct request_queue *q, struct bio **bio)
{
struct bio *split, *res;
unsigned nsegs;
switch (bio_op(*bio)) {
case REQ_OP_DISCARD:
case REQ_OP_SECURE_ERASE:
split = blk_bio_discard_split(q, *bio, &q->bio_split, &nsegs);
break;
case REQ_OP_WRITE_ZEROES:
split = blk_bio_write_zeroes_split(q, *bio, &q->bio_split, &nsegs);
break;
case REQ_OP_WRITE_SAME:
split = blk_bio_write_same_split(q, *bio, &q->bio_split, &nsegs);
break;
default:
split = blk_bio_segment_split(q, *bio, &q->bio_split, &nsegs);
break;
}
/* physical segments can be figured out during splitting */
res = split ? split : *bio;
res->bi_phys_segments = nsegs;
bio_set_flag(res, BIO_SEG_VALID);
if (split) {
/* there isn't chance to merge the splitted bio */
split->bi_opf |= REQ_NOMERGE;
/*
* Since we're recursing into make_request here, ensure
* that we mark this bio as already having entered the queue.
* If not, and the queue is going away, we can get stuck
* forever on waiting for the queue reference to drop. But
* that will never happen, as we're already holding a
* reference to it.
*/
bio_set_flag(*bio, BIO_QUEUE_ENTERED);
bio_chain(split, *bio);
trace_block_split(q, split, (*bio)->bi_iter.bi_sector);
generic_make_request(*bio);
*bio = split;
}
}
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_vec bv, bvprv = { NULL };
int cluster, prev = 0;
unsigned int seg_size, nr_phys_segs;
struct bio *fbio, *bbio;
struct bvec_iter iter;
if (!bio)
return 0;
switch (bio_op(bio)) {
case REQ_OP_DISCARD:
case REQ_OP_SECURE_ERASE:
case REQ_OP_WRITE_ZEROES:
return 0;
case REQ_OP_WRITE_SAME:
return 1;
}
fbio = bio;
cluster = blk_queue_cluster(q);
seg_size = 0;
nr_phys_segs = 0;
for_each_bio(bio) {
bio_for_each_segment(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))
goto new_segment;
if (!BIOVEC_PHYS_MERGEABLE(&bvprv, &bv))
goto new_segment;
if (!BIOVEC_SEG_BOUNDARY(q, &bvprv, &bv))
goto new_segment;
seg_size += bv.bv_len;
bvprv = bv;
continue;
}
new_segment:
if (nr_phys_segs == 1 && seg_size >
fbio->bi_seg_front_size)
fbio->bi_seg_front_size = seg_size;
nr_phys_segs++;
bvprv = bv;
prev = 1;
seg_size = bv.bv_len;
}
bbio = bio;
}
if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size)
fbio->bi_seg_front_size = seg_size;
if (seg_size > bbio->bi_seg_back_size)
bbio->bi_seg_back_size = seg_size;
return nr_phys_segs;
}
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);
}
void blk_recount_segments(struct request_queue *q, struct bio *bio)
{
unsigned short seg_cnt;
/* estimate segment number by bi_vcnt for non-cloned bio */
if (bio_flagged(bio, BIO_CLONED))
seg_cnt = bio_segments(bio);
else
seg_cnt = bio->bi_vcnt;
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;
bio->bi_next = NULL;
bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, false);
bio->bi_next = nxt;
}
bio_set_flag(bio, BIO_SEG_VALID);
}
EXPORT_SYMBOL(blk_recount_segments);
static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
struct bio *nxt)
{
struct bio_vec end_bv = { NULL }, nxt_bv;
if (!blk_queue_cluster(q))
return 0;
if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
queue_max_segment_size(q))
return 0;
if (!bio_has_data(bio))
return 1;
bio_get_last_bvec(bio, &end_bv);
bio_get_first_bvec(nxt, &nxt_bv);
if (!BIOVEC_PHYS_MERGEABLE(&end_bv, &nxt_bv))
return 0;
/*
* bio and nxt are contiguous in memory; check if the queue allows
* these two to be merged into one
*/
if (BIOVEC_SEG_BOUNDARY(q, &end_bv, &nxt_bv))
return 1;
return 0;
}
static inline void
__blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,
struct scatterlist *sglist, struct bio_vec *bvprv,
struct scatterlist **sg, int *nsegs, int *cluster)
{
int nbytes = bvec->bv_len;
if (*sg && *cluster) {
if ((*sg)->length + nbytes > queue_max_segment_size(q))
goto new_segment;
if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
goto new_segment;
if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
goto new_segment;
(*sg)->length += nbytes;
} else {
new_segment:
if (!*sg)
*sg = sglist;
else {
/*
* 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);
*sg = sg_next(*sg);
}
sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset);
(*nsegs)++;
}
*bvprv = *bvec;
}
static inline int __blk_bvec_map_sg(struct request_queue *q, struct bio_vec bv,
struct scatterlist *sglist, struct scatterlist **sg)
{
*sg = sglist;
sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset);
return 1;
}
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 cluster = blk_queue_cluster(q), nsegs = 0;
for_each_bio(bio)
bio_for_each_segment(bvec, bio, iter)
__blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg,
&nsegs, &cluster);
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 *sg = NULL;
int nsegs = 0;
if (rq->rq_flags & RQF_SPECIAL_PAYLOAD)
nsegs = __blk_bvec_map_sg(q, rq->special_vec, sglist, &sg);
else if (rq->bio && bio_op(rq->bio) == REQ_OP_WRITE_SAME)
nsegs = __blk_bvec_map_sg(q, bio_iovec(rq->bio), sglist, &sg);
else if (rq->bio)
nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg);
if (unlikely(rq->rq_flags & RQF_COPY_USER) &&
(blk_rq_bytes(rq) & q->dma_pad_mask)) {
unsigned int pad_len =
(q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1;
sg->length += pad_len;
rq->extra_len += pad_len;
}
if (q->dma_drain_size && q->dma_drain_needed(rq)) {
if (op_is_write(req_op(rq)))
memset(q->dma_drain_buffer, 0, q->dma_drain_size);
sg_unmark_end(sg);
sg = sg_next(sg);
sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
q->dma_drain_size,
((unsigned long)q->dma_drain_buffer) &
(PAGE_SIZE - 1));
nsegs++;
rq->extra_len += q->dma_drain_size;
}
if (sg)
sg_mark_end(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 int ll_new_hw_segment(struct request_queue *q,
struct request *req,
struct bio *bio)
{
int nr_phys_segs = bio_phys_segments(q, bio);
if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q))
goto no_merge;
if (blk_integrity_merge_bio(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(q, req);
return 0;
}
int ll_back_merge_fn(struct request_queue *q, struct request *req,
struct bio *bio)
{
if (req_gap_back_merge(req, bio))
return 0;
if (blk_integrity_rq(req) &&
integrity_req_gap_back_merge(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(q, req);
return 0;
}
if (!bio_flagged(req->biotail, BIO_SEG_VALID))
blk_recount_segments(q, req->biotail);
if (!bio_flagged(bio, BIO_SEG_VALID))
blk_recount_segments(q, bio);
return ll_new_hw_segment(q, req, bio);
}
int ll_front_merge_fn(struct request_queue *q, struct request *req,
struct bio *bio)
{
if (req_gap_front_merge(req, bio))
return 0;
if (blk_integrity_rq(req) &&
integrity_req_gap_front_merge(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(q, req);
return 0;
}
if (!bio_flagged(bio, BIO_SEG_VALID))
blk_recount_segments(q, bio);
if (!bio_flagged(req->bio, BIO_SEG_VALID))
blk_recount_segments(q, req->bio);
return ll_new_hw_segment(q, req, bio);
}
/*
* blk-mq uses req->special to carry normal driver per-request payload, it
* does not indicate a prepared command that we cannot merge with.
*/
static bool req_no_special_merge(struct request *req)
{
struct request_queue *q = req->q;
return !q->mq_ops && req->special;
}
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;
unsigned int seg_size =
req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
/*
* First check if the either of the requests are re-queued
* requests. Can't merge them if they are.
*/
if (req_no_special_merge(req) || req_no_special_merge(next))
return 0;
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 (blk_phys_contig_segment(q, req->biotail, next->bio)) {
if (req->nr_phys_segments == 1)
req->bio->bi_seg_front_size = seg_size;
if (next->nr_phys_segments == 1)
next->biotail->bi_seg_back_size = seg_size;
total_phys_segments--;
}
if (total_phys_segments > queue_max_segments(q))
return 0;
if (blk_integrity_merge_rq(q, req, next) == false)
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(struct request *req)
{
if (blk_do_io_stat(req)) {
struct hd_struct *part;
int cpu;
cpu = part_stat_lock();
part = req->part;
part_round_stats(req->q, cpu, part);
part_dec_in_flight(req->q, part, rq_data_dir(req));
hd_struct_put(part);
part_stat_unlock();
}
}
/*
* 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 (!q->mq_ops)
lockdep_assert_held(q->queue_lock);
if (!rq_mergeable(req) || !rq_mergeable(next))
return NULL;
if (req_op(req) != req_op(next))
return NULL;
/*
* not contiguous
*/
if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
return NULL;
if (rq_data_dir(req) != rq_data_dir(next)
|| req->rq_disk != next->rq_disk
|| req_no_special_merge(next))
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 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.
*/
if (req_op(req) == REQ_OP_DISCARD) {
if (!req_attempt_discard_merge(q, req, next))
return NULL;
} else if (!ll_merge_requests_fn(q, req, next))
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 (req_op(req) != REQ_OP_DISCARD)
elv_merge_requests(q, req, next);
/*
* 'next' is going away, so update stats accordingly
*/
blk_account_io_merge(next);
req->ioprio = ioprio_best(req->ioprio, next->ioprio);
if (blk_rq_cpu_valid(next))
req->cpu = next->cpu;
/*
* ownership of bio passed from next to req, return 'next' for
* the caller to free
*/
next->bio = NULL;
return next;
}
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;
}
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 elevator_queue *e = q->elevator;
struct request *free;
if (!e->uses_mq && e->type->ops.sq.elevator_allow_rq_merge_fn)
if (!e->type->ops.sq.elevator_allow_rq_merge_fn(q, rq, next))
return 0;
free = attempt_merge(q, rq, next);
if (free) {
__blk_put_request(q, 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 and not a special request */
if (rq->rq_disk != bio->bi_disk || req_no_special_merge(rq))
return false;
/* only merge integrity protected bio into ditto rq */
if (blk_integrity_merge_bio(rq->q, rq, bio) == false)
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;
return true;
}
enum elv_merge blk_try_merge(struct request *rq, struct bio *bio)
{
if (req_op(rq) == REQ_OP_DISCARD &&
queue_max_discard_segments(rq->q) > 1)
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;
}
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