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 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>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
---
fs/xfs/xfs_super.c | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index b2dd0c0bf509..606a95ac816f 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -2114,6 +2114,21 @@ xfs_fs_reconfigure(
if (error)
return error;
+ /* attr2 -> noattr2 */
+ if (xfs_has_noattr2(new_mp)) {
+ if (xfs_has_crc(mp)) {
+ xfs_warn(mp,
+ "attr2 is always enabled for a V5 filesystem - can't be changed.");
+ return -EINVAL;
+ }
+ mp->m_features &= ~XFS_FEAT_ATTR2;
+ mp->m_features |= XFS_FEAT_NOATTR2;
+ } else if (xfs_has_attr2(new_mp)) {
+ /* noattr2 -> attr2 */
+ mp->m_features &= ~XFS_FEAT_NOATTR2;
+ mp->m_features |= XFS_FEAT_ATTR2;
+ }
+
/* inode32 -> inode64 */
if (xfs_has_small_inums(mp) && !xfs_has_small_inums(new_mp)) {
mp->m_features &= ~XFS_FEAT_SMALL_INUMS;
@@ -2126,6 +2141,17 @@ xfs_fs_reconfigure(
mp->m_maxagi = xfs_set_inode_alloc(mp, mp->m_sb.sb_agcount);
}
+ /*
+ * 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.
+ */
+ error = xfs_finish_flags(mp);
+ if (error)
+ return error;
+
/* ro -> rw */
if (xfs_is_readonly(mp) && !(flags & SB_RDONLY)) {
error = xfs_remount_rw(mp);
--
2.43.5
