Re: WARNING: CPU: 3 PID: 20953 at /usr/src/linux/fs/btrfs/raid56.c:848 __free_raid_bio+0x8e/0xa0

["Jérôme Carretero" <cJ-ko@zougloub.eu>]

Hi,

On Wed, 22 Nov 2017 15:35:35 -0800
Liu Bo <bo.li.liu@oracle.com> wrote:

> On Mon, Nov 20, 2017 at 02:00:07AM -0500, Jérôme Carretero wrote:
> > ------------[ cut here ]------------ [633254.461294] WARNING: CPU:
> > 3 PID: 20953 at /usr/src/linux/fs/btrfs/raid56.c:848
> > __free_raid_bio+0x8e/0xa0  
> 
> 
> The vanilla 4.14.0 shows it is
> WARN_ON(!bio_list_empty(&rbio->bio_list)); but we just emptied
> rbio->bio_list two lines above, i.e. struct bio *cur =
> bio_list_get(&rbio->bio_list);
> 
> Either we have some weird race, or the line number is misleading me.
> 
> Can you please check the code which warning fs/btrfs/raid56.c:848
> points to?

Same code as yours:
        WARN_ON(!bio_list_empty(&rbio->bio_list));

So yeah, at least git is not broken, now it could be a very weird
compiler bug or a less-weird race indeed...


Regards,

-- 
Jérôme