On Tue, Apr 29, 2025 at 02:32:08PM +0530, Nirjhar Roy (IBM) wrote:
> Bug: When we compile the kernel with CONFIG_XFS_SUPPORT_V4=y,
> remount with "-o remount,noattr2" on a v5 XFS does not
> fail explicitly.
>
> Reproduction:
> mkfs.xfs -f /dev/loop0
> mount /dev/loop0 /mnt/scratch
> mount -o remount,noattr2 /dev/loop0 /mnt/scratch
>
> However, with CONFIG_XFS_SUPPORT_V4=n, the remount
> correctly fails explicitly. This is because the way the
> following 2 functions are defined:
>
> static inline bool xfs_has_attr2 (struct xfs_mount *mp)
> {
> return !IS_ENABLED(CONFIG_XFS_SUPPORT_V4) ||
> (mp->m_features & XFS_FEAT_ATTR2);
> }
> static inline bool xfs_has_noattr2 (const struct xfs_mount *mp)
> {
> return mp->m_features & XFS_FEAT_NOATTR2;
> }
>
> xfs_has_attr2() returns true when CONFIG_XFS_SUPPORT_V4=n
> and hence, the the following if condition in
> xfs_fs_validate_params() succeeds and returns -EINVAL:
>
> /*
> * We have not read the superblock at this point, so only the attr2
> * mount option can set the attr2 feature by this stage.
> */
>
> if (xfs_has_attr2(mp) && xfs_has_noattr2(mp)) {
> xfs_warn(mp, "attr2 and noattr2 cannot both be specified.");
> return -EINVAL;
> }
>
> With CONFIG_XFS_SUPPORT_V4=y, xfs_has_attr2() always return
> false and hence no error is returned.
>
> Fix: Check if the existing mount has crc enabled(i.e, of
> type v5 and has attr2 enabled) and the
> remount has noattr2, if yes, return -EINVAL.
>
> I have tested xfs/{189,539} in fstests with v4
> and v5 XFS with both CONFIG_XFS_SUPPORT_V4=y/n and
> they both behave as expected.
>
> This patch also fixes remount from noattr2 -> attr2 (on a v4 xfs).
>
> Related discussion in [1]
>
> [1] https://lore.kernel.org/all/Z65o6nWxT00MaUrW@xxxxxxxxxxxxxxxxxxx/
>
> Signed-off-by: Nirjhar Roy (IBM) <nirjhar.roy.lists@xxxxxxxxx>
> ---
> fs/xfs/xfs_super.c | 25 +++++++++++++++++++++++++
> 1 file changed, 25 insertions(+)
>
> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> index b2dd0c0bf509..1fd45567ae00 100644
> --- a/fs/xfs/xfs_super.c
> +++ b/fs/xfs/xfs_super.c
> @@ -2114,6 +2114,22 @@ xfs_fs_reconfigure(
> if (error)
> return error;
>
> + /* attr2 -> noattr2 */
> + if (xfs_has_noattr2(new_mp)) {
> + if (xfs_has_crc(mp)) {
> + xfs_warn(mp, "attr2 and noattr2 cannot both be specified.");
Nit: normal xfs style is to move the message to a new line when іt
overflows 80 characters:
if (xfs_has_crc(mp)) {
xfs_warn(mp,
"attr2 and noattr2 cannot both be specified.");
> + return -EINVAL;
> + }
> + else {
No need for an else after a return. And for cases where there is an
else the kernel coding style keeps it on the same line as the closing
brace.
> + /* Now that mp has been modified according to the remount options, we do a
> + * final option validation with xfs_finish_flags() just like it is done
> + * during mount. We cannot use xfs_finish_flags() on new_mp as it contains
> + * only the user given options.
> + */
Please keep comments to 80 characters. Also the kernel coding style
keeps the
/*
at the beginning of a comment on a separate line.
