Re: [stable] [PATCH] vfs: Fix vmtruncate() regression

[Greg KH]

On Mon, Jan 18, 2010 at 02:51:46PM +1100, Nick Piggin wrote:
> On Fri, Jan 15, 2010 at 09:26:02AM +0900, OGAWA Hirofumi wrote:
> > Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> writes:
> > 
> > > On Wed, 13 Jan 2010 21:14:09 +0900
> > > OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx> 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@xxxxxxx>
> > >> Signed-off-by: OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
> > >> ---
> > >> 
> > >>  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.
> 
> Thanks guys, it's quite important so please apply to stable 2.6.32 and
> consider it as a high priority to release.

Now queued up for the next .32 -stable release.

greg k-h
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