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block: Replace SG_GAPS with new queue limits mask

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The SG_GAPS queue flag caused checks for bio vector alignment against
PAGE_SIZE, but the device may have different constraints. This patch
adds a queue limits so a driver with such constraints can set to allow
requests that would have been unnecessarily split. The new gaps check
takes the request_queue as a parameter to simplify the logic around
invoking this function.

This new limit makes the queue flag redundant, so removing it and
all usage. Device-mappers will inherit the correct settings through
blk_stack_limits().

Signed-off-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Keith Busch
2015-08-19 14:24:05 -07:00
committed by Jens Axboe
parent d2be537c3b
commit 03100aada9
7 changed files with 43 additions and 42 deletions
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23
block/blk-merge.c
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@@ -82,8 +82,7 @@ static struct bio *blk_bio_segment_split(struct request_queue *q,
* If the queue doesn't support SG gaps and adding this
* offset would create a gap, disallow it.
*/
if (q->queue_flags & (1 << QUEUE_FLAG_SG_GAPS) &&
prev && bvec_gap_to_prev(&bvprv, bv.bv_offset))
if (prev && bvec_gap_to_prev(q, &bvprv, bv.bv_offset))
goto split;
if (prev && blk_queue_cluster(q)) {
@@ -484,12 +483,12 @@ static bool req_no_special_merge(struct request *req)
return !q->mq_ops && req->special;
}
static int req_gap_to_prev(struct request *req, struct request *next)
static int req_gap_to_prev(struct request *req, struct bio *next)
{
struct bio *prev = req->biotail;
return bvec_gap_to_prev(&prev->bi_io_vec[prev->bi_vcnt - 1],
next->bio->bi_io_vec[0].bv_offset);
return bvec_gap_to_prev(req->q, &prev->bi_io_vec[prev->bi_vcnt - 1],
next->bi_io_vec[1].bv_offset);
}
static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
@@ -506,8 +505,7 @@ static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
if (req_no_special_merge(req) || req_no_special_merge(next))
return 0;
if (test_bit(QUEUE_FLAG_SG_GAPS, &q->queue_flags) &&
req_gap_to_prev(req, next))
if (req_gap_to_prev(req, next->bio))
return 0;
/*
@@ -692,8 +690,6 @@ int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
{
struct request_queue *q = rq->q;
if (!rq_mergeable(rq) || !bio_mergeable(bio))
return false;
@@ -718,13 +714,8 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
return false;
/* Only check gaps if the bio carries data */
if (q->queue_flags & (1 << QUEUE_FLAG_SG_GAPS) && bio_has_data(bio)) {
struct bio_vec *bprev;
bprev = &rq->biotail->bi_io_vec[rq->biotail->bi_vcnt - 1];
if (bvec_gap_to_prev(bprev, bio->bi_io_vec[0].bv_offset))
return false;
}
if (bio_has_data(bio) && req_gap_to_prev(rq, bio))
return false;
return true;
}