On Sat, 21 Nov 2015 12:30:14 +0100 Laurent Dufour <lduf...@linux.vnet.ibm.com> wrote:
> On 20/11/2015 13:10, Michael Ellerman wrote: > > On Thu, 2015-11-19 at 00:23 -0800, Christoph Hellwig wrote: > > > >> It's pretty much guaranteed a block layer bug, most likely in the > >> merge bios to request infrastucture where we don't obey the merging > >> limits properly. > >> > >> Does either of you have a known good and first known bad kernel? > > > > Not me, I've only hit it one or two times. All I can say is I have hit it in > > 4.4-rc1. > > > > Laurent, can you narrow it down at all? > > It seems that the panic is triggered by the commit bdced438acd8 ("block: > setup bi_phys_segments after splitting") which has been pulled by the > merge d9734e0d1ccf ("Merge branch 'for-4.4/core' of > git://git.kernel.dk/linux-block"). > > My system is panicing promptly when running a kernel built at > d9734e0d1ccf, while reverting the commit bdced438acd8, it can run hours > without panicing. > > This being said, I can't explain what's going wrong. > > May Ming shed some light here ? Laurent, looks there is one bug in blk_bio_segment_split(), would you mind testing the following patch to see if it fixes your issue? --- >From 6fc701231dcc000bc8bc4b9105583380d9aa31f4 Mon Sep 17 00:00:00 2001 From: Ming Lei <ming....@canonical.com> Date: Sun, 22 Nov 2015 00:47:13 +0800 Subject: [PATCH] block: fix segment split Inside blk_bio_segment_split(), previous bvec pointer('bvprvp') always points to the iterator local variable, which is obviously wrong, so fix it by pointing to the local variable of 'bvprv'. Signed-off-by: Ming Lei <ming....@canonical.com> --- block/blk-merge.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/block/blk-merge.c b/block/blk-merge.c index de5716d8..f2efe8a 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -98,7 +98,7 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, seg_size += bv.bv_len; bvprv = bv; - bvprvp = &bv; + bvprvp = &bvprv; sectors += bv.bv_len >> 9; continue; } @@ -108,7 +108,7 @@ new_segment: nsegs++; bvprv = bv; - bvprvp = &bv; + bvprvp = &bvprv; seg_size = bv.bv_len; sectors += bv.bv_len >> 9; } -- 1.9.1 Thanks, Ming -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html