Re: [PATCH 3.16 102/305] xfs: xfs_iflush_cluster fails to abort on error

Dave Chinner
2016-08-14T10:16:17Z

On Sat, Aug 13, 2016 at 06:42:51PM +0100, Ben Hutchings wrote:
> 3.16.37-rc1 review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: Dave Chinner <dchinner@redhat.com>
>
> commit b1438f477934f5a4d5a44df26f3079a7575d5946 upstream.
>
> When a failure due to an inode buffer occurs, the error handling
> fails to abort the inode writeback correctly. This can result in the
> inode being reclaimed whilst still in the AIL, leading to
> use-after-free situations as well as filesystems that cannot be
> unmounted as the inode log items left in the AIL never get removed.
>
> Fix this by ensuring fatal errors from xfs_imap_to_bp() result in
> the inode flush being aborted correctly.
....
>
> /*
> - * Get the buffer containing the on-disk inode.
> + * Get the buffer containing the on-disk inode. We are doing a try-lock
> + * operation here, so we may get an EAGAIN error. In that case, we
> + * simply want to return with the inode still dirty.
> + *
> + * If we get any other error, we effectively have a corruption situation
> + * and we cannot flush the inode, so we treat it the same as failing
> + * xfs_iflush_int().
> */
> error = xfs_imap_to_bp(mp, NULL, &ip->i_imap, &dip, &bp, XBF_TRYLOCK,
> 0);
> - if (error || !bp) {
> + if (error == -EAGAIN) {

Wrong. As was pointed out for other -stable trees after users
reported regressions, the error signs in XFS changed from positive
to negative in 3.17-rc1.

-Dave.
--
Dave Chinner
david@fromorbit.com