On Thu, Aug 31, 2023 at 10:07:39PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@xxxxxxxxxx>
>
> While reviewing the FIEXCHANGE code in XFS, I realized that the function
> that enables logged xattrs doesn't actually check that the superblock
> has a LOG_INCOMPAT feature bit field. Add a check to refuse the
> operation if we don't have a V5 filesystem...
>
> ...but on second though, let's require either reflink or rmap so that we
> only have to deal with LARP mode on relatively /modern/ kernel. 4.14 is
> about as far back as I feel like going.
>
> Seeing as LARP is a debugging-only option anyway, this isn't likely to
> affect any real users.
>
> Fixes: d9c61ccb3b09 ("xfs: move xfs_attr_use_log_assist out of xfs_log.c")
> Really-Fixes: f3f36c893f26 ("xfs: Add xfs_attr_set_deferred and xfs_attr_remove_deferred")
> Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
Reviewed-by: Bill O'Donnell <bodonnel@xxxxxxxxxx>
> ---
> fs/xfs/xfs_xattr.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/fs/xfs/xfs_xattr.c b/fs/xfs/xfs_xattr.c
> index 43e5c219aaed..a3975f325f4e 100644
> --- a/fs/xfs/xfs_xattr.c
> +++ b/fs/xfs/xfs_xattr.c
> @@ -46,6 +46,17 @@ xfs_attr_grab_log_assist(
> if (xfs_sb_version_haslogxattrs(&mp->m_sb))
> return 0;
>
> + /*
> + * Check if the filesystem featureset is new enough to set this log
> + * incompat feature bit. Strictly speaking, the minimum requirement is
> + * a V5 filesystem for the superblock field, but we'll require rmap
> + * or reflink to avoid having to deal with really old kernels.
> + */
> + if (!xfs_has_reflink(mp) && !xfs_has_rmapbt(mp)) {
> + error = -EOPNOTSUPP;
> + goto drop_incompat;
> + }
> +
> /* Enable log-assisted xattrs. */
> error = xfs_add_incompat_log_feature(mp,
> XFS_SB_FEAT_INCOMPAT_LOG_XATTRS);
>
