linux-ext4 - Re: [PATCH REGRESSION FIX] ext4: fix mtime update in nodelalloc mode

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Date:	Mon, 1 Oct 2012 11:32:13 +0200
From:	Jan Kara <jack@...e.cz>
To:	Theodore Ts'o <tytso@....edu>
Cc:	Jonathan Nieder <jrnieder@...il.com>, Willy Tarreau <w@....eu>,
	Ext4 Developers List <linux-ext4@...r.kernel.org>,
	linux-nilfs@...r.kernel.org, Jan Kara <jack@...e.cz>,
	KONISHI Ryusuke <konishi.ryusuke@....ntt.co.jp>,
	stable@...r.kernel.org
Subject: Re: [PATCH REGRESSION FIX] ext4: fix mtime update in nodelalloc
 mode

On Sun 30-09-12 16:30:26, Ted Tso wrote:
> The rewritten commit description:
> 
> ext4: fix mtime update in nodelalloc mode
> 
> Commits 5e8830dc85d0 and 41c4d25f78c0 introduced a regression into
> 3.6-rc1 for ext4 in nodealloc mode, such that mtime updates would not
> take place for files modified via mmap if the page was already in the
> page cache.  This would also affect ext3 file systems mounted using
> the ext4 file system driver.
> 
> The problem was that ext4_page_mkwrite() had a shortcut which would
> avoid calling __block_page_mkwrite() under some circumstances, and the
> above two commit transferred the responsibility of calling
> file_update_time() to __block_page_mkwrite --- which woudln't get
> called in some circumstances.
> 
> Since __block_page_mkwrite() only has three callers,
> block_page_mkwrite(), ext4_page_mkwrite, and nilfs_page_mkwrite(), the
> best way to solve this is to move the responsibility for calling
> file_update_time() to its caller.
> 
> This problem was found via xfstests #215 with a file system mounted
> with -o nodelalloc.
> 
> Signed-off-by: "Theodore Ts'o" <tytso@....edu>
> Cc: Jan Kara <jack@...e.cz>
> Cc: KONISHI Ryusuke <konishi.ryusuke@....ntt.co.jp>
> Cc: stable@...r.kernel.org
> 
> Note: If this gets pushed to Linus before the merge window opens, I'll
> drop the cc of stable@...r.kernel.org, since the regression was
> introduced in 3.6-rc1.
  Ah, good catch. Thanks for fixing this. I agree with the fix so you can
add:
  Reviewed-by: Jan Kara <jack@...e.cz>

								Honza
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