From: Nikanth Karthikesan <knikanth@xxxxxxx> ll_merge_requests_fn() decreases the req->nr_phys_segments if blk_phys_contig_segment() returns true, but it is perfectly possible that blk_hw_contig_segment() is false. A new hw_segment implies a new phys_segment. So decrementing nr_phys_segments wrongly here triggers the BUG_ON() in scsi_init_sgtable(), as blk_rq_map_sg() would map 1 phys_segment more than req->nr_phys_segment. This is easily reproducible. Other callers of blk_rq_map_sg() should also be affected by this bug. Signed-off-by: Nikanth Karthikesan <knikanth@xxxxxxx> --- block/blk-merge.c | 10 ++++------ 1 files changed, 4 insertions(+), 6 deletions(-) diff --git a/block/blk-merge.c b/block/blk-merge.c index 5efc9e7..6e6d04b 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -392,11 +392,6 @@ static int ll_merge_requests_fn(struct request_queue *q, struct request *req, return 0; total_phys_segments = req->nr_phys_segments + next->nr_phys_segments; - if (blk_phys_contig_segment(q, req->biotail, next->bio)) - total_phys_segments--; - - if (total_phys_segments > q->max_phys_segments) - return 0; total_hw_segments = req->nr_hw_segments + next->nr_hw_segments; if (blk_hw_contig_segment(q, req->biotail, next->bio)) { @@ -410,9 +405,12 @@ static int ll_merge_requests_fn(struct request_queue *q, struct request *req, if (next->nr_hw_segments == 1) next->biotail->bi_hw_back_size = len; total_hw_segments--; + if (blk_phys_contig_segment(q, req->biotail, next->bio)) + total_phys_segments--; } - if (total_hw_segments > q->max_hw_segments) + if (total_phys_segments > q->max_phys_segments || + total_hw_segments > q->max_hw_segments) return 0; /* Merge is OK... */ -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html