On Tue, May 17, 2016 at 11:57:07PM +0200, Adam Borowski wrote:
> On Tue, May 17, 2016 at 05:00:49PM -0400, Chris Mason wrote:
> > On Tue, May 17, 2016 at 10:47:27PM +0200, Adam Borowski wrote:
> > > > Hmmm, some of your traces mentioned compression, do you have compression
> > > > enabled?
> > >
> > > Yeah, I mount with noatime,compress=lzo.
> > >
> > > > Also, if you can gdb your vmlinux (or btrfs.ko) and find this line:
> > > >
> > > > gdb> list *__btrfs_buffered_write+0x748
> > >
> > > 0xffffffff8152eb78 is in __btrfs_buffered_write (fs/btrfs/file.c:1564).
> > > 1559
> > > 1560 reserve_metadata:
> > > 1561 ret = btrfs_delalloc_reserve_metadata(inode, reserve_bytes);
> > > 1562 if (ret) {
> > > 1563 if (!only_release_metadata)
> > > 1564 btrfs_free_reserved_data_space(inode, pos,
> > > 1565 write_bytes);
> > > 1566 else
> > > 1567 btrfs_end_write_no_snapshoting(root);
> > > 1568 break;
> > >
> >
> > Aha, so you're getting an enospc with compression on and the accounting
> > doesn't line up. I should be able to trigger this.
>
> This partition was fully balanced just a few days ago so I didn't even think
> to look at df.
>
> [~]# df -h
> /dev/sda1 216G 161G 53G 76% /
>
> [~]# btrfs files df /
> Data, single: total=209.12GiB, used=156.46GiB
> System, single: total=32.00MiB, used=48.00KiB
> Metadata, single: total=6.00GiB, used=3.51GiB
> GlobalReserve, single: total=512.00MiB, used=0.00B
>
> However, after partially balancing it a bit:
>
> [~]# btrfs files df /
> Data, single: total=172.00GiB, used=156.03GiB
> System, single: total=32.00MiB, used=48.00KiB
> Metadata, single: total=5.00GiB, used=3.50GiB
> GlobalReserve, single: total=512.00MiB, used=0.00B
>
> I can't reproduce the failure anymore.
Yeah, I'm not sure yet if this is related to the page faulting problem,
but Dave Jones triggered this error back in v4.4. I'll still fix it, it
should be an alignment issue with write_bytes.
-chris
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