linux-kernel - Re: [PATCH] aio: fix kernel bug when page is temporally busy

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Message-Id: <20070214193051.4b008d61.akpm@linux-foundation.org>
Date:	Wed, 14 Feb 2007 19:30:51 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Ananiev, Leonid I" <leonid.i.ananiev@...el.com>
Cc:	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] aio: fix kernel bug when page is temporally busy

On Wed, 14 Feb 2007 20:51:33 +0300 "Ananiev, Leonid I" <leonid.i.ananiev@...el.com> wrote:

> Fix kernel bug when IO page is temporally busy:
> invalidate_inode_pages2_range() returns EIOCBRETRY but not  EIO.
> invalidate_inode_pages2() returns EIO as earlier.
> 
> Signed-off-by: Leonid Ananiev <leonid.i.ananiev@...el.com>
> ---
> --- linux-2.6.20/mm/truncate.c  2007-02-04 10:44:54.000000000 -0800
> +++ linux-2.6.20p/mm/truncate.c 2007-02-08 22:56:52.000000000 -0800
> @@ -366,7 +366,7 @@ static int do_launder_page(struct addres
>   * Any pages which are found to be mapped into pagetables are unmapped prior to
>   * invalidation.
>   *
> - * Returns -EIO if any pages could not be invalidated.
> + * Returns -EIOCBRETRY if any pages could not be invalidated.
>   */
>  int invalidate_inode_pages2_range(struct address_space *mapping,
>                                   pgoff_t start, pgoff_t end)
> @@ -423,7 +423,7 @@ int invalidate_inode_pages2_range(struct
>                         }
>                         ret = do_launder_page(mapping, page);
>                         if (ret == 0 && !invalidate_complete_page2(mapping, page))
> -                               ret = -EIO;
> +                               ret = -EIOCBRETRY;
>                         unlock_page(page);
>                 }
>                 pagevec_release(&pvec);
> @@ -444,6 +444,7 @@ EXPORT_SYMBOL_GPL(invalidate_inode_pages
>   */
>  int invalidate_inode_pages2(struct address_space *mapping)
>  {
> -       return invalidate_inode_pages2_range(mapping, 0, -1);
> +       int ret =  invalidate_inode_pages2_range(mapping, 0, -1);
> +       return (ret < 0)?-EIO:ret;
>  }
>  EXPORT_SYMBOL_GPL(invalidate_inode_pages2);

If someone later uses invalidate_inode_pages2_range() elsewhere, they're
going to need to know to convert -EIOCBRETRY into -EIO, if they weren't
called by aio.  Or something.

Please, tell us what problem this is fixing so that we can look into
alternative solutions.

For example, one acceptable-but-ugly solution might be to do:

static inline int invalidate_inode_pages2_range(struct address_space *mapping,
				pgoff_t start, pgoff_t end)
{
	return __invalidate_inode_pages2_range(mapping, start, end, 0);
}

static inline int invalidate_inode_pages2_range_for_aio(struct address_space *mapping,
				pgoff_t start, pgoff_t end)
{
	return __invalidate_inode_pages2_range(mapping, start, end, 1);
}

and to then use invalidate_inode_pages2_range_for_aio() from the
appropriate callsite.

But without a complete description of the bug which this is fixing, it's
hard to say how practical such an approach would be.

-
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