On Sat, Oct 11 2008, FUJITA Tomonori wrote: > This is against the latest git (b922df7383749a1c0b7ea64c50fa839263d3816b). > > = > From: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx> > Subject: [PATCH] block: fix nr_phys_segments miscalculation bug > > This fixes the bug reported by Nikanth Karthikesan <knikanth@xxxxxxx>: > > http://lkml.org/lkml/2008/10/2/203 > > The root cause of the bug is that blk_phys_contig_segment > miscalculates q->max_segment_size. > > blk_phys_contig_segment checks: > > req->biotail->bi_size + next_req->bio->bi_size > q->max_segment_size > > But blk_recalc_rq_segments might expect that req->biotail and the > previous bio in the req are supposed be merged into one > segment. blk_recalc_rq_segments might also expect that next_req->bio > and the next bio in the next_req are supposed be merged into one > segment. In such case, we merge two requests that can't be merged > here. Later, blk_rq_map_sg gives more segments than it should. > > We need to keep track of segment size in blk_recalc_rq_segments and > use it to see if two requests can be merged. This patch implements it > in the similar way that we used to do for hw merging (virtual > merging). This looks really good, just like I imagined. I'll give it a fuller review later today and do a bit of targetted testing, if it goes as planned it'll go in soonish. Thanks a lot! -- Jens Axboe -- 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
