[XFS] Any process to a particular XFS device hung in D state forever.

[Hugo Kuo]

Hi Brian,

Here's the result of xfs_repair on the same disk after rebooting.
https://gist.github.com/HugoKuo/e1d683d9653e66a80dfcfcbee4294fe8
It's looks normal.

We rebooted the server and no hanging process in past 12hrs. I'll keep eyes
on the server.
I know it's helpful to to trace-cmd for xfs. But there's too may xfs
operations are happening in the server. It's crazy like 100MB data per
second. I stopped the trace-cmd. As you said, we need to find out the
source of the problem. trace-cmd would be a nice option. Is there a way to
flush recored data if nothing happens in the past hours ?

trace-cmd record -e xfs\*



Regards // Hugo




On Wed, Apr 20, 2016 at 7:24 PM, Brian Foster <bfoster at redhat.com> wrote:

> On Wed, Apr 20, 2016 at 01:49:49PM +0800, Hugo Kuo wrote:
> > Hi XFS team,
> >
> >
> > Here's the lsof output of the grouped result of any openfile happens on
> > problematic disks. The full log of xfs_repair -n is included in this gist
> > as well. The xfs_repair recommend to contact xfs mailing list in the end
> of
> > the command.
> >
> > https://gist.github.com/HugoKuo/95613d7864aa0a1343615642b3309451
> >
> > Perhaps I should go ahead to reboot the machine and run the xfs_repair
> > again.  Please find my answers inlines.
> >
>
> Yes, repair is crashing in this case. Best to try xfs_repair after
> you've rebooted and mounted/umounted the fs to replay the log. If it's
> still crashing at that point, we'll probably want a metadata image of
> the fs, if possible (though there's a good chance a newer xfsprogs has
> the problem fixed).
>
> >
> > On Wed, Apr 20, 2016 at 3:34 AM, Brian Foster <bfoster at redhat.com>
> wrote:
> >
> > >
> > > So there's definitely some traces waiting on AGF locks and whatnot, but
> > > also many traces that appear to be waiting on I/O. For example:
> > >
> >
> > Yes, those I/O waiting is the original problem of this thread. It looks
> > like the disk was locked. All these I/O waiting for same disk (a
> multipath
> > entry).
> >
> >
> > >
> > > kernel: swift-object- D 0000000000000008     0  2096   1605 0x00000000
> > > kernel: ffff8877cc2378b8 0000000000000082 ffff8877cc237818
> ffff887ff016eb68
> > > kernel: ffff883fd4ab6b28 0000000000000046 ffff883fd4bd9400
> 00000001e7ea49d0
> > > kernel: ffff8877cc237848 ffffffff812735d1 ffff885fa2e4a5f8
> ffff8877cc237fd8
> > > kernel: Call Trace:
> > > kernel: [<ffffffff812735d1>] ? __blk_run_queue+0x31/0x40
> > > kernel: [<ffffffff81539455>] schedule_timeout+0x215/0x2e0
> > > kernel: [<ffffffff812757c9>] ? blk_peek_request+0x189/0x210
> > > kernel: [<ffffffff8126d9b3>] ? elv_queue_empty+0x33/0x40
> > > kernel: [<ffffffffa00040a0>] ? dm_request_fn+0x240/0x340 [dm_mod]
> > > kernel: [<ffffffff815390d3>] wait_for_common+0x123/0x180
> > > kernel: [<ffffffff810672b0>] ? default_wake_function+0x0/0x20
> > > kernel: [<ffffffffa0001036>] ? dm_unplug_all+0x36/0x50 [dm_mod]
> > > kernel: [<ffffffffa0415b56>] ? _xfs_buf_read+0x46/0x60 [xfs]
> > > kernel: [<ffffffffa040b417>] ? xfs_trans_read_buf+0x197/0x410 [xfs]
> > > kernel: [<ffffffff815391ed>] wait_for_completion+0x1d/0x20
> > > kernel: [<ffffffffa041503b>] xfs_buf_iowait+0x9b/0x100 [xfs]
> > > kernel: [<ffffffffa040b417>] ? xfs_trans_read_buf+0x197/0x410 [xfs]
> > > kernel: [<ffffffffa0415b56>] _xfs_buf_read+0x46/0x60 [xfs]
> > > kernel: [<ffffffffa0415c1b>] xfs_buf_read+0xab/0x100 [xfs]
> > >
> > >
> > > Are all of these swift processes running against independent storage,
> or
> > > one big array? Also, can you tell (e.g., with iotop) whether progress
> is
> > > being made here, albiet very slowly, or if the storage is indeed locked
> > > up..?
> > >
> > > There're 240+ swift processes in running.
> > All stuck swift processes were attempting to access same disk.  I can
> > confirm it's indeed locked rather than slowly. By monitoring io via
> iotop.
> > There's 0 activity one the problematic mount point.
> >
> >
> > > In any event, given the I/O hangs, the fact that you're on an old
> distro
> > > kernel and you have things like multipath enabled, it might be
> > > worthwhile to see if you can rule out any multipath issues.
> > >
> > >
> > To upgrade the kernel for CentOS6.5 may not the option for the time being
> > but it definitely worth to give it try by picking up one of nodes for
> > testing later. As for the multipath, yes I did suspect some mystery
> problem
> > with multipath + XFS under a certain loading. But it's more like a XFS
> and
> > inode related hence I start to investigate from XFS. If there's no chance
> > to move forward in XFS, I might break the multipath and observe the
> result
> > for awhile.
> >
>
> It's hard to pinpoint something to the fs when there's a bunch of hung
> I/Os. You probably want to track down the source of those problems
> first.
>
> Brian
>
> >
> > >
> > > 'umount -l' doesn't necessarily force anything. It just lazily unmounts
> > > the fs from the namespace and cleans up the mount once all references
> > > are dropped. I suspect the fs is still mounted internally.
> > >
> > > Brian
> > >
> > >
> > Thanks // Hugo
>
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