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block: fix merging data-less bios 

The data segment gaps the block layer tracks doesn't apply to bio's that
don't have data. Skip calculating this to fix a NULL pointer access.

Fixes: 2f6b2565d4 ("block: accumulate memory segment gaps per bio")
Reported-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Yu Kuai <yukuai@fnnas.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Keith Busch 2025-11-11 06:06:20 -08:00 committed by Jens Axboe
parent 727a440278
commit fd9ecd0052
1 changed files with 3 additions and 0 deletions
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3
block/blk-merge.c
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@ -737,6 +737,9 @@ u8 bio_seg_gap(struct request_queue *q, struct bio *prev, struct bio *next,
{ {
struct bio_vec pb, nb; struct bio_vec pb, nb;
if (!bio_has_data(prev))
return 0;
gaps_bit = min_not_zero(gaps_bit, prev->bi_bvec_gap_bit); gaps_bit = min_not_zero(gaps_bit, prev->bi_bvec_gap_bit);
gaps_bit = min_not_zero(gaps_bit, next->bi_bvec_gap_bit); gaps_bit = min_not_zero(gaps_bit, next->bi_bvec_gap_bit);