Re: [PATCH 10/14] xfs: remote attribute read too short

Ben Myers
2013-05-20T23:00:47Z

On Mon, May 20, 2013 at 09:51:17AM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
>
> Reading a maximally size remote attribute fails when CRCs are
> enabled with this verification error:
>
> XFS (vdb): remote attribute header does not match required off/len/owner)
>
> There are two reasons for this, the first being that the
> length of the buffer being read is determined from the
> args->rmtblkcnt which doesn't take into account CRC headers. Hence
> the mapped length ends up being too short and so we need to
> calculate it directly from the value length.
>
> The second is that the byte count of valid data within a buffer is
> capped by the length of the data and so doesn't take into account
> that the buffer might be longer due to headers. Hence we need to
> calculate the data space in the buffer first before calculating the
> actual byte count of data.
>
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> ---
> fs/xfs/xfs_attr_remote.c | 15 +++++++++------
> 1 file changed, 9 insertions(+), 6 deletions(-)
>
> diff --git a/fs/xfs/xfs_attr_remote.c b/fs/xfs/xfs_attr_remote.c
> index aad95b0..bcdc07c 100644
> --- a/fs/xfs/xfs_attr_remote.c
> +++ b/fs/xfs/xfs_attr_remote.c
> @@ -52,9 +52,11 @@ xfs_attr3_rmt_blocks(
> struct xfs_mount *mp,
> int attrlen)
> {
> - int buflen = XFS_ATTR3_RMT_BUF_SPACE(mp,
> - mp->m_sb.sb_blocksize);
> - return (attrlen + buflen - 1) / buflen;
> + if (xfs_sb_version_hascrc(&mp->m_sb)) {
> + int buflen = XFS_ATTR3_RMT_BUF_SPACE(mp, mp->m_sb.sb_blocksize);
> + return (attrlen + buflen - 1) / buflen;
> + }
> + return XFS_B_TO_FSB(mp, attrlen);
> }

xfs_attr_rmtval_set, previously the only caller of xfs_attr3_rmt_blocks already
checks for crcs. Can one of the two conditionals be dispensed with?