On Thu, 5 Mar 2009 12:10:40 +0100 Jens Axboe <jens.axboe@xxxxxxxxxx> wrote: > On Thu, Mar 05 2009, FUJITA Tomonori wrote: > > On Thu, 5 Mar 2009 11:30:24 +0100 > > Jens Axboe <jens.axboe@xxxxxxxxxx> wrote: > > > > > > > While merging that, I think we can do better than this. Essentially we > > > > > just need to have __blk_recalc_rq_segments() track the back bio as well, > > > > > then we don't have to pass in a pointer for segment sizes. > > > > > > > > > > Totally untested, comments welcome... > > > > > > > > Yeah, I think that updating bi_seg_front_size and bi_seg_back_size at > > > > one place, __blk_recalc_rq_segments, is better. I thought about the > > > > same way. But we are already in -rc7 and this must go into mainline > > > > now. So I chose a less-intrusive way (similar to what we have done in > > > > the past). > > > > > > > > As you know, the merging code is really complicated and we could > > > > overlook stuff easily. ;) It might be better to simplify the merging > > > > code a bit. > > > > > > If someone (Ingo?) is willing to test the last variant, I'd much rather > > > add that. It does simplify it (imho), and it kills 23 lines while only > > > adding 9. But a quick response would be nice, then I can ask Linus to > > > pull it later today. > > > > I prefer to keep your change for 2.6.30 but if you want to push it > > now, it's fine by me. > > I honestly can't see much of a difference in change complexity, so I > don't see much point in putting one fix in 2.6.29 and then doing another > for 2.6.30... My preference are: 1) simply reverting commit 1e42807918d17e8c93bf14fbb74be84b141334c1 (and blaming ext4 for now). 2) applying my patch, affecting only blk_recount_segments(). 3) applying your patch, affecting blk_recount_segments() and blk_recalc_rq_segments(). But as I said, the third options is fine by me. Your patch looks ok to me. > > Ingo, you can quickly hit this bug without the patch? > > > > I've not hit this bug while I've been performing intensive I/Os for > > the last three hours. And I thought that Thomas took two hours to hit > > this. So maybe it's too early to give 'Tested-by'. With > > max_segment_size decreased, we might hit this easier. > > Yep, that may help. I haven't seen this thread until I was cc'ed on it, > so I haven't even read up on the generic problem yet... I think that last night James and Thomas finally found that the block layer miscalculates nr_phys_segments. And then I figured out exactly where the bug is, I guess hopefully. -- 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
