Re: [4.1-rc7] btrfs related VM_BUG_ON in filemap.c

Dave Jones
2015-06-30T19:29:00Z

On Tue, Jun 30, 2015 at 03:23:00PM -0400, Josef Bacik wrote:
> On 06/30/2015 03:20 PM, Dave Jones wrote:
> > On Wed, Jun 17, 2015 at 09:35:41AM -0400, Dave Jones wrote:
> >
> > > page:ffffea00027cc640 count:4 mapcount:0 mapping:ffff8800af11d8a0 index:0x0
> > > flags: 0x4000000000000846(error|referenced|active|private)
> > > page dumped because: VM_BUG_ON_PAGE(!PageLocked(page))
> > > ------------[ cut here ]------------
> > > kernel BUG at mm/filemap.c:745!
> >
> > Still occasionally bumping into this.
> > The 'count:4 mapcount:0' is constant in every instance I've seen
> > so far. Could that be a clue ?
> >
> > I've seen various page flags, but it's always !locked
> >
> > Ideas on additional debugging I could add ?
>
> Huh I just noticed that PG_Error seems to be set, is that the same for
> every time? I wonder where that's getting set and why. I'll dig into
> the areas we set that and see if I can spot anything. Thanks,

Seems to be set every time yeah.
I can try annotating those places that set it to see which one is triggering
when I get home.

Dave