From: Dave Chinner <david@fromorbit.com>
To: Jeff Liu <jeff.liu@oracle.com>
Cc: "xfs@oss.sgi.com" <xfs@oss.sgi.com>
Subject: Re: [PATCH v2 RESEND] xfs: fix dead loop at xfs_vm_writepage() on 32bit machine
Date: Thu, 26 Sep 2013 07:32:24 +1000 [thread overview]
Message-ID: <20130925213224.GG26872@dastard> (raw)
In-Reply-To: <52429A6C.3050908@oracle.com>
On Wed, Sep 25, 2013 at 04:10:20PM +0800, Jeff Liu wrote:
> From: Jie Liu <jeff.liu@oracle.com>
>
> Write a file with an offset greater than 16TB on 32-bit system and
> then trigger page write-back via sync(1) as below will cause the
> task hang in a little while:
[snip]
> This patch just fixed both issues.
>
> Reported-by: Michael L. Semon <mlsemon35@gmail.com>
> Signed-off-by: Jie Liu <jeff.liu@oracle.com>
> ---
> v2: don't reset the s_max_bytes to MAX_LFS_FILESIZE, instead, revise the page offset
> check up strategy to avoid the potential overflow.
> v1: http://oss.sgi.com/archives/xfs/2013-07/msg00154.html
>
> fs/xfs/xfs_aops.c | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
> index 41a6950..6059d00 100644
> --- a/fs/xfs/xfs_aops.c
> +++ b/fs/xfs/xfs_aops.c
> @@ -969,7 +969,9 @@ xfs_vm_writepage(
> offset = i_size_read(inode);
> end_index = offset >> PAGE_CACHE_SHIFT;
> last_index = (offset - 1) >> PAGE_CACHE_SHIFT;
> - if (page->index >= end_index) {
> + if (page->index < end_index)
> + end_offset = (xfs_off_t)(page->index + 1) << PAGE_CACHE_SHIFT;
> + else {
> unsigned offset_into_page = offset & (PAGE_CACHE_SIZE - 1);
The logic here is already difficult to understand, and the fact that
the code that has 32 bit overflow issues is not obvious . Can you
add a comment noting the overflow issue being handled here?
>
> /*
> @@ -978,7 +980,8 @@ xfs_vm_writepage(
> * page so that reclaim stops reclaiming it. Otherwise
> * xfs_vm_releasepage() is called on it and gets confused.
> */
> - if (page->index >= end_index + 1 || offset_into_page == 0)
> + if (page->index > end_index ||
> + (page->index == end_index && offset_into_page == 0))
> goto redirty;
And again here?
That means in future we will be aware of the problem when reading
the code...
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
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next prev parent reply other threads:[~2013-09-25 21:32 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-25 8:10 [PATCH v2 RESEND] xfs: fix dead loop at xfs_vm_writepage() on 32bit machine Jeff Liu
2013-09-25 21:32 ` Dave Chinner [this message]
2013-09-26 4:12 ` Jeff Liu
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