linux-ext4 - Re: [PATCH v4 15/20] ext4: use ext4_zero_partial_blocks in punch

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Date:	Fri, 14 Jun 2013 12:16:53 +0200 (CEST)
From:	Lukáš Czerner <lczerner@...hat.com>
To:	"Theodore Ts'o" <tytso@....edu>
cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
	akpm@...ux-foundation.org, hughd@...gle.com
Subject: Re: [PATCH v4 15/20] ext4: use ext4_zero_partial_blocks in
 punch_hole

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

> Date: Thu, 13 Jun 2013 23:01:54 -0400
> From: Theodore Ts'o <tytso@....edu>
> To: Lukas Czerner <lczerner@...hat.com>
> Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
>     linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
>     akpm@...ux-foundation.org, hughd@...gle.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@...hat.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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