Re: [PATCH v4 15/20] ext4: use ext4_zero_partial_blocks in punch_hole

Lukáš Czerner
2013-06-14T10:16:53Z

On Thu, 13 Jun 2013, Theodore Ts'o wrote:

> Date: Thu, 13 Jun 2013 23:01:54 -0400
> From: Theodore Ts'o <tytso@mit.edu>
> To: Lukas Czerner <lczerner@redhat.com>
> Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
> linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
> akpm@linux-foundation.org, hughd@google.com
> Subject: Re: [PATCH v4 15/20] ext4: use ext4_zero_partial_blocks in punch_hole
>
> On Tue, May 14, 2013 at 06:37:29PM +0200, Lukas Czerner wrote:
> > We're doing to get rid of ext4_discard_partial_page_buffers() since it is
> > duplicating some code and also partially duplicating work of
> > truncate_pagecache_range(), moreover the old implementation was much
> > clearer.
> >
> > Now when the truncate_inode_pages_range() can handle truncating non page
> > aligned regions we can use this to invalidate and zero out block aligned
> > region of the punched out range and then use ext4_block_truncate_page()
> > to zero the unaligned blocks on the start and end of the range. This
> > will greatly simplify the punch hole code. Moreover after this commit we
> > can get rid of the ext4_discard_partial_page_buffers() completely.
> >
> > We also introduce function ext4_prepare_punch_hole() to do come common
> > operations before we attempt to do the actual punch hole on
> > indirect or extent file which saves us some code duplication.
> >
> > This has been tested on ppc64 with 1k block size with fsx and xfstests
> > without any problems.
> >
> > Signed-off-by: Lukas Czerner <lczerner@redhat.com>
>
> Hi Lukas,
>
> I've been seeing xfstests failures on test generic/300 in nojournal
> mode.
>
> BEGIN TEST: Ext4 4k block w/ no journal Thu Jun 13 22:38:47 EDT 2013
> Device: /dev/vdb
> mk2fs options: -q -O ^has_journal
> mount options: -o block_validity,noload
> FSTYP -- ext4
> PLATFORM -- Linux/i686 candygram 3.10.0-rc2-00477-g1e1cad7
> MKFS_OPTIONS -- -q -O ^has_journal /dev/vdc
> MOUNT_OPTIONS -- -o acl,user_xattr -o block_validity,noload /dev/vdc /vdc
>
> generic/300 [20:42:18][ 116.877278] fio (3320) used greatest stack depth: 5580 bytes left
> [ 116.967122] fio (3321) used greatest stack depth: 5560 bytes left
> [ 117.573861] fio (3325) used greatest stack depth: 5504 bytes left
> [20:44:01] [failed, exit status 1] - output mismatch (see /root/xfstests/results/generic/300.out.bad)
> --- tests/generic/300.out 2013-06-04 22:42:55.000000000 -0400
> +++ /root/xfstests/results/generic/300.out.bad 2013-06-13 20:44:01.306666665 -0400
> @@ -2,3 +2,4 @@
>
> Run fio with random aio-dio pattern
>
> +_check_generic_filesystem: filesystem on /dev/vdc is inconsistent (see /root/xfstests/results/generic/300.full)
> ...
> (Run 'diff -u tests/generic/300.out /root/xfstests/results/generic/300.out.bad' to see the entire diff)
>
> It bisects down to this patch, and if I take the dev branch, and
> revert patches #15 through #19 in this series, the problem goes away.
>
> Can you investigate and recommend a better fix?

Hi Ted,

I'll take a look at this. Thanks for letting me know.

-Lukas

>
> Thanks,
>
> - Ted
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