linux-kernel - Re: [PATCH] vfs: Fix vmtruncate() regression

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Message-ID: <87ska86wo5.fsf@devron.myhome.or.jp>
Date:	Fri, 15 Jan 2010 09:26:02 +0900
From:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>,
	Al Viro <viro@...iv.linux.org.uk>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	stable@...nel.org
Subject: Re: [PATCH] vfs: Fix vmtruncate() regression

Andrew Morton <akpm@...ux-foundation.org> writes:

> On Wed, 13 Jan 2010 21:14:09 +0900
> OGAWA Hirofumi <hirofumi@...l.parknet.co.jp> wrote:
>
>> 
>> If __block_prepare_write() was failed in block_write_begin(), the
>> allocated blocks can be outside of ->i_size.
>> 
>> But new truncate_pagecache() in vmtuncate() does nothing if new < old.
>> It means the above usage is not working anymore.
>> 
>> So, this patch fixes it by removing "new < old" check. It would need
>> more cleanup/change. But, now -rc and truncate working is in progress,
>> so, this tried to fix it minimum change.
>> 
>> Acked-by: Nick Piggin <npiggin@...e.de>
>> Signed-off-by: OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
>> ---
>> 
>>  mm/truncate.c |   28 +++++++++++++---------------
>>  1 file changed, 13 insertions(+), 15 deletions(-)
>> 
>> diff -puN mm/truncate.c~truncate_pagecache-fix mm/truncate.c
>> --- linux-2.6/mm/truncate.c~truncate_pagecache-fix	2010-01-12 05:43:06.000000000 +0900
>> +++ linux-2.6-hirofumi/mm/truncate.c	2010-01-12 05:43:06.000000000 +0900
>> @@ -522,22 +522,20 @@ EXPORT_SYMBOL_GPL(invalidate_inode_pages
>>   */
>>  void truncate_pagecache(struct inode *inode, loff_t old, loff_t new)
>>  {
>> -	if (new < old) {
>> -		struct address_space *mapping = inode->i_mapping;
>> +	struct address_space *mapping = inode->i_mapping;
>>  
>> -		/*
>> -		 * unmap_mapping_range is called twice, first simply for
>> -		 * efficiency so that truncate_inode_pages does fewer
>> -		 * single-page unmaps.  However after this first call, and
>> -		 * before truncate_inode_pages finishes, it is possible for
>> -		 * private pages to be COWed, which remain after
>> -		 * truncate_inode_pages finishes, hence the second
>> -		 * unmap_mapping_range call must be made for correctness.
>> -		 */
>> -		unmap_mapping_range(mapping, new + PAGE_SIZE - 1, 0, 1);
>> -		truncate_inode_pages(mapping, new);
>> -		unmap_mapping_range(mapping, new + PAGE_SIZE - 1, 0, 1);
>> -	}
>> +	/*
>> +	 * unmap_mapping_range is called twice, first simply for
>> +	 * efficiency so that truncate_inode_pages does fewer
>> +	 * single-page unmaps.  However after this first call, and
>> +	 * before truncate_inode_pages finishes, it is possible for
>> +	 * private pages to be COWed, which remain after
>> +	 * truncate_inode_pages finishes, hence the second
>> +	 * unmap_mapping_range call must be made for correctness.
>> +	 */
>> +	unmap_mapping_range(mapping, new + PAGE_SIZE - 1, 0, 1);
>> +	truncate_inode_pages(mapping, new);
>> +	unmap_mapping_range(mapping, new + PAGE_SIZE - 1, 0, 1);
>>  }
>>  EXPORT_SYMBOL(truncate_pagecache);
>
> The fix was applied to 2.6.33-rcX
> (cedabed49b39b4319bccc059a63344b6232b619c), appears to be needed in
> 2.6.32.x but no cc:stable's are present?

Ah, yes. I forgot to add "Cc: stable". Please apply this to 2.6.32.x.
-- 
OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
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