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blk-merge: fix blk_recount_segments
QUEUE_FLAG_NO_SG_MERGE is set at default for blk-mq devices, so bio->bi_phys_segment computed may be bigger than queue_max_segments(q) for blk-mq devices, then drivers will fail to handle the case, for example, BUG_ON() in virtio_queue_rq() can be triggerd for virtio-blk: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1359146 This patch fixes the issue by ignoring the QUEUE_FLAG_NO_SG_MERGE flag if the computed bio->bi_phys_segment is bigger than queue_max_segments(q), and the regression is caused by commit 05f1dd53152173(block: add queue flag for disabling SG merging). Reported-by: Kick In <pierre-andre.morey@canonical.com> Tested-by: Chris J Arges <chris.j.arges@canonical.com> Signed-off-by: Ming Lei <ming.lei@canonical.com> Signed-off-by: Jens Axboe <axboe@fb.com>
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@ -10,10 +10,11 @@
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#include "blk.h"
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static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
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struct bio *bio)
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struct bio *bio,
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bool no_sg_merge)
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{
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struct bio_vec bv, bvprv = { NULL };
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int cluster, high, highprv = 1, no_sg_merge;
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int cluster, high, highprv = 1;
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unsigned int seg_size, nr_phys_segs;
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struct bio *fbio, *bbio;
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struct bvec_iter iter;
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@ -35,7 +36,6 @@ static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
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cluster = blk_queue_cluster(q);
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seg_size = 0;
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nr_phys_segs = 0;
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no_sg_merge = test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags);
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high = 0;
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for_each_bio(bio) {
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bio_for_each_segment(bv, bio, iter) {
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@ -88,18 +88,23 @@ new_segment:
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void blk_recalc_rq_segments(struct request *rq)
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{
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rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio);
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bool no_sg_merge = !!test_bit(QUEUE_FLAG_NO_SG_MERGE,
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&rq->q->queue_flags);
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rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio,
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no_sg_merge);
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}
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void blk_recount_segments(struct request_queue *q, struct bio *bio)
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{
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if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags))
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if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) &&
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bio->bi_vcnt < queue_max_segments(q))
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bio->bi_phys_segments = bio->bi_vcnt;
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else {
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struct bio *nxt = bio->bi_next;
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bio->bi_next = NULL;
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bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio);
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bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, false);
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bio->bi_next = nxt;
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}
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