Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932160AbaAGCwT (ORCPT ); Mon, 6 Jan 2014 21:52:19 -0500 Received: from mail-pa0-f54.google.com ([209.85.220.54]:55758 "EHLO mail-pa0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756646AbaAGCwQ (ORCPT ); Mon, 6 Jan 2014 21:52:16 -0500 Date: Mon, 6 Jan 2014 18:52:10 -0800 From: Kent Overstreet To: Muthu Kumar Cc: Chris Mason , Fengguang Wu , Jens Axboe , linux-btrfs , linux-fsdevel , LKML , lkp@linux.intel.com Subject: Re: [block:for-3.14/core] kernel BUG at fs/bio.c:1748 Message-ID: <20140107025210.GJ9037@kmo> References: <20140102053101.GA29352@localhost> <20140106221036.GE9037@kmo> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 06, 2014 at 04:47:38PM -0800, Muthu Kumar wrote: > OK, after a bit more staring I believe the correct fix is the following. This code still confuses me but I think you're correct, the fix certainly matches the evidence we have. > Fengguang, Please try this one? > > Regards, > Muthu > > ------------ > In btrfs_end_bio(), we increment bi_remaining if is_orig_bio. If not, > we restore the orig_bio but failed to increment bi_remaining for > orig_bio, which triggers a BUG_ON later when bio_endio is called. Fix > is to increment bi_remaining when we restore the orig bio as well. > > Reported-by: fengguang.wu@intel.com > CC: Kent Overstreet > CC: Jens Axboe > CC: Chris Mason Signed-off-by: Muthukumar Ratty > ---------------- > fs/btrfs/volumes.c | 4 ++-- > 1 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c > index 37972d5..2011cc0 100644 > --- a/fs/btrfs/volumes.c > +++ b/fs/btrfs/volumes.c > @@ -5297,9 +5297,9 @@ static void btrfs_end_bio(struct bio *bio, int err) > if (!is_orig_bio) { > bio_put(bio); > bio = bbio->orig_bio; > - } else { > - atomic_inc(&bio->bi_remaining); > } > + atomic_inc(&bio->bi_remaining); > + > bio->bi_private = bbio->private; > bio->bi_end_io = bbio->end_io; > btrfs_io_bio(bio)->mirror_num = bbio->mirror_num; > > -------------------------- > > > > On Mon, Jan 6, 2014 at 2:10 PM, Kent Overstreet wrote: > > Chris, the patch below seems to be incorrect - with it we get hangs, so > > bi_remaining (probably) isn't getting decremented when it should be. You sent > > Jens fixes for btrfs which I somehow lost when I rebased, do you remember how > > this is supposed to work? Looking at the code I'm not quite sure what's going on > > here. > > > > On Fri, Jan 03, 2014 at 11:51:31AM -0800, Muthu Kumar wrote: > >> Looks like Kent missed the btrfs endio in the original commit. How > >> about this patch: > >> > >> --------- > >> > >> In btrfs_end_bio, call bio_endio_nodec on the restored bio so the > >> bi_remaining is accounted for correctly. > >> > >> Reported-by: fengguang.wu@intel.com > >> Cc: Kent Overstreet > >> CC: Jens Axboe > >> Signed-off-by: Muthukumar Ratty > >> -------- > >> > >> fs/btrfs/volumes.c | 6 +++++- > >> 1 files changed, 5 insertions(+), 1 deletions(-) > >> > >> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c > >> index f2130de..edfed52 100644 > >> --- a/fs/btrfs/volumes.c > >> +++ b/fs/btrfs/volumes.c > >> @@ -5316,7 +5316,11 @@ static void btrfs_end_bio(struct bio *bio, int err) > >> } > >> kfree(bbio); > >> > >> - bio_endio(bio, err); > >> + /* > >> + * Call endio_nodec on the restored bio so the bi_remaining is > >> + * accounted for correctly > >> + */ > >> + bio_endio_nodec(bio, err); > >> } else if (!is_orig_bio) { > >> bio_put(bio); > >> } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/