linux-kernel - Re: [block:for-3.14/core] kernel BUG at fs/bio.c:1748

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Date:	Wed, 8 Jan 2014 13:14:54 -0800
From:	Kent Overstreet <kmo@...erainc.com>
To:	Chris Mason <clm@...com>
Cc:	"muthu.lkml@...il.com" <muthu.lkml@...il.com>,
	"linux-btrfs@...r.kernel.org" <linux-btrfs@...r.kernel.org>,
	"fengguang.wu@...el.com" <fengguang.wu@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"lkp@...ux.intel.com" <lkp@...ux.intel.com>,
	"axboe@...nel.dk" <axboe@...nel.dk>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>
Subject: Re: [block:for-3.14/core] kernel BUG at fs/bio.c:1748

On Wed, Jan 08, 2014 at 09:11:49PM +0000, Chris Mason wrote:
> On Wed, 2014-01-08 at 13:01 -0800, Muthu Kumar wrote:
> > On Wed, Jan 8, 2014 at 12:51 PM, Chris Mason <clm@...com> wrote:
> > > On Wed, 2014-01-08 at 12:40 -0800, Muthu Kumar wrote:
> > >> On Wed, Jan 8, 2014 at 12:16 PM, Chris Mason <clm@...com> wrote:
> > >> > On Wed, 2014-01-08 at 11:54 -0800, Muthu Kumar wrote:
> > >> >> Chris,
> > >> >>
> > >> >> [    8.336061] WARNING: CPU: 0 PID: 0 at fs/bio.c:1778 bio_endio+0xbe/0x100()
> > >> >> [    8.336062] bio_endio: bio for (unknown) without endio
> > >> >>
> > >> >> This is my recent change to avoid memory leak in bio_endio. But I
> > >> >> think the problem is higher up, most likely bio_endio is called twice
> > >> >> on the same bio (which was freed before).
> > >> >>
> > >> >
> > >> > I think these are just two separate problems.  Lets ignore the WARN_ON
> > >> > for now.
> > >> >
> > >>
> > >> Not really... the BUG that is triggered:
> > >>
> > >> kernel BUG at fs/bio.c:523!
> > >>
> > >> It is in bio_put() (added to bio_endio() as part of recent change)
> > >> which gets an already freed bio.
> > >>
> > >
> > > Oh! I see.  Let me try with that one reverted.  Thanks!
> > >
> > > -chris
> > >
> > 
> > But, like I said, problem is in different place. I am running a "dd"
> > on ext4 fs for a while now, but didn't hit the problem. Any idea to
> > repro locally? I would also suggest running just the for-3.1/core to
> > isolate the issue.
> 
> Just reverting that change fixes it for me.  Jens mentioned it was
> broken for on-stack bios.

On-stack bios? I don't recall ever coming across such a thing, who what
where why?

i would expect on stack bios to work though, i'm really curious how it
was broken
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