Re: xfs bug in 2.6.26-rc9

Lachlan McIlroy
2008-07-14T07:29:01Z

Mikael Abrahamsson wrote:
> On Fri, 11 Jul 2008, Dave Chinner wrote:
>
>> That aside, what was the assert failure reported prior to the oops?
>> i.e. paste the lines in the log before the ---[ cut here ]--- line?
>> One of them will start with 'Assertion failed:', I think....
>
> These ones?
>
> Jul 8 04:44:56 via kernel: [554197.888008] Assertion failed: whichfork
> == XFS_ATTR_FORK || ip->i_delayed_blks == 0, file: fs/xfs/xfs_bmap.c,
> line: 5879
> Jul 9 03:25:21 via kernel: [42940.748007] Assertion failed: whichfork
> == XFS_ATTR_FORK || ip->i_delayed_blks == 0, file: fs/xfs/xfs_bmap.c,
> line: 5879

xfs_ilock(ip, XFS_IOLOCK_SHARED);

if (whichfork == XFS_DATA_FORK &&
(ip->i_delayed_blks || ip->i_size > ip->i_d.di_size)) {
/* xfs_fsize_t last_byte = xfs_file_last_byte(ip); */
error = xfs_flush_pages(ip, (xfs_off_t)0,
-1, 0, FI_REMAPF);
if (error) {
xfs_iunlock(ip, XFS_IOLOCK_SHARED);
return error;
}
}

ASSERT(whichfork == XFS_ATTR_FORK || ip->i_delayed_blks == 0);

This is a race between xfs_fsr and a mmap write. xfs_fsr acquires the
iolock and then flushes the file and because it has the iolock it doesn't
expect any new delayed allocations to occur. A mmap write can allocate
delayed allocations without acquiring the iolock so is able to get in
after the flush but before the ASSERT.

>
> I'll happily rebuild the kernel without the debug option and do
> xfs_check to weed out any possible logical problem with the volume, if
> you don't need any further information from the current state of my volume.
>
> I should also say that this assert failue happened two nights in a row
> so I guess it's fairly reproducible (didn't happen on the 10th, and
> today, the 11th it seems to have panic:ed around 03:30 (I start the
> defragmentation via cron at 03:00) which I think is related.
>