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blk-merge: recaculate segment if it isn't less than max segments 

The problem is introduced by commit 764f612c6c3c231b(blk-merge:
don't compute bi_phys_segments from bi_vcnt for cloned bio),
and merge is needed if number of current segment isn't less than
max segments.

Strictly speaking, bio->bi_vcnt shouldn't be used here since
it may not be accurate in cases of both cloned bio or bio cloned
from, but bio_segments() is a bit expensive, and bi_vcnt is still
the biggest number, so the approach should work.

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Ming Lei 2014-10-22 08:30:30 +08:00 committed by Jens Axboe
parent 432f16e64f
commit 76d8137a31
1 changed files with 3 additions and 2 deletions
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5
block/blk-merge.c
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@ -99,16 +99,17 @@ void blk_recount_segments(struct request_queue *q, struct bio *bio)
{
bool no_sg_merge = !!test_bit(QUEUE_FLAG_NO_SG_MERGE,
&q->queue_flags);
bool merge_not_need = bio->bi_vcnt < queue_max_segments(q);
if (no_sg_merge && !bio_flagged(bio, BIO_CLONED) &&
bio->bi_vcnt < queue_max_segments(q))
merge_not_need)
bio->bi_phys_segments = bio->bi_vcnt;
else {
struct bio *nxt = bio->bi_next;
bio->bi_next = NULL;
bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio,
no_sg_merge);
no_sg_merge && merge_not_need);
bio->bi_next = nxt;
}