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

[Theodore Ts'o]

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@xxxxxxxxxx>

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?

Thanks,

					- Ted
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