Re: Possible memory allocation deadlock in kmem_alloc and hung task in xfs_log_commit_cil and xlog_cil_push

[juncheng bai]

Hi, All

As far as I know, the patch b3f03bac8132207a20286d5602eda64500c19724 
solves one case which big directory size.

I am not very familiar with xfs, but I think why can't we use vmalloc
when kmalloc fails?

Thanks.
--------------
juncheng bai

On 2015/7/8 20:34, Gavin Guo wrote:
> Hi Dave,
>
> On Wed, Jul 8, 2015 at 7:37 AM, Dave Chinner <david@xxxxxxxxxxxxx> wrote:
> > On Tue, Jul 07, 2015 at 05:29:43PM +0800, Gavin Guo wrote:
> > > Hi all,
> > >
> > > Recently, we observed that there is the error message in
> > > Ubuntu-3.13.0-48.80:
> > >
> > > "XFS: possible memory allocation deadlock in kmem_alloc (mode:0x8250)"
> > >
> > > repeatedly shows in the dmesg. Temporarily, our workaround is to tune the
> > > parameters, such as, vfs_cache_pressure, min_free_kbytes, and dirty_ratio.
> > >
> > > And we also found that there are different error messages regarding the
> > > hung tasks which happened in xfs_log_commit_cil and xlog_cil_push.
> > >
> > > The log is available at: http://paste.ubuntu.com/11835007/
> > >
> > > The following link seems the same problem we suffered:
> > >
> > > XFS hangs with XFS: possible memory allocation deadlock in kmem_alloc
> > > http://oss.sgi.com/archives/xfs/2015-03/msg00172.html
> > >
> > > I read the mail and found that there might be some modification regarding
> > > to move the memory allocation outside the ctx lock. And I also read the
> > > latest patch from February of 2015 to see if there is any new change
> > > about that. Unfortunately, I didn't find anything regarding the change (may
> > > be I'm not familiar with the XFS, so didn't find the commit). If it's
> > > possible for someone who is familiar with the code to point out the commits
> > > related to the bug if already exist or any status about the plan.
> >
> > No commits - the approach I thought we might be able to take to
> > avoid the problem didn't work out. I have another idea of how we
> > might solve the problem, but I haven't ad a chance to prototype it
> > yet.
> >
> > Cheers,
> >
> > Dave.
> > --
> > Dave Chinner
> > david@xxxxxxxxxxxxx
>
> Really thanks for your information, I'll keep watching out the status.
>
> Thanks,
> Gavin Guo
>
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