Commit 76d8137a authored Oct 22, 2014 by Ming Lei Committed by Jens Axboe Oct 21, 2014

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



The problem is introduced by commit 764f612c(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>

parent 432f16e6

block/blk-merge.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -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;
		}

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