Re: Linux 6.9.y btrfs: "NULL pointer dereference in attach_eb_folio_to_filemap" and "BUG: soft lockup" issues

[David Sterba <dsterba@suse.cz>]

On Mon, Jul 01, 2024 at 01:39:40PM +0200, Jaroslav Pulchart wrote:
> >
> > >
> > > Hi,
> > >
> > > On Mon, Jun 17, 2024 at 01:33:59PM +0200, Jaroslav Pulchart wrote:
> > > > Hello,
> > > >
> > > > We recently upgraded part of our production environment to kernel
> > > > 6.9.y. Since then, we've been encountering random kernel "NULL pointer
> > > > dereference" and "soft lockup" errors when using BTRFS. These issues
> > > > occur sporadically, sometimes after several days, and I haven't been
> > > > able to reproduce them consistently. Due to this unpredictability,
> > > > bisecting is not a feasible option.
> > > >
> > > > Attached are console logs from some instances of these issues:
> > > > * "NULL pointer dereference" in "btrfs.issue.1.log"
> > > > * "soft lockup" in "btrfs.issue.1.log"
> > > > Any assistance with investigating and resolving these problems would
> > > > be greatly appreciated.
> > >
> > > thanks for the report, the symptoms match the problem that was fixed
> > > recently by commit f3a5367c679d ("btrfs: protect folio::private when
> > > attaching extent buffer folios").
> > >
> > > > [1072053.328255] CPU: 15 PID: 2354438 Comm: kworker/u195:18 Tainted: G            E      6.9.3-1.gdc.el9.x86_64 #1
> > >
> > > 6.9.3 does not have the fix yet (unless you're using a manually patched
> > > kernel), it's in 6.9.5.
> >
> > Thanks, we will try the 6.9.5 asap and report results after a few days.
> 
> 
> Hello,
> 
> we do not see the issue any more with >= 6.9.5

Great, thanks for testing.