Re: [PATCH v11 08/15] xfs: Report case sensitivity in fileattr_get

["Chuck Lever" <cel@kernel.org>]

On Mon, Apr 27, 2026, at 11:56 AM, Darrick J. Wong wrote:
> On Fri, Apr 24, 2026 at 09:53:10PM -0400, Chuck Lever wrote:
>> From: Chuck Lever <chuck.lever@oracle.com>
>> 
>> Upper layers such as NFSD need to query whether a filesystem
>> is case-sensitive. Add FS_XFLAG_CASEFOLD to xfs_ip2xflags()
>> when the filesystem is formatted with the ASCIICI feature
>> flag. This serves both FS_IOC_FSGETXATTR (via xfs_fill_fsxattr() in
>> xfs_fileattr_get()) and XFS_IOC_BULKSTAT (which populates bs_xflags
>> directly from xfs_ip2xflags()), so bulkstat consumers and per-inode
>> queries see a consistent view of the filesystem's case-folding
>> behavior.
>> 
>> XFS always preserves case. XFS is case-sensitive by default, but
>> supports ASCII case-insensitive lookups when formatted with the
>> ASCIICI feature flag.
>> 
>> Reviewed-by: Roland Mainz <roland.mainz@nrubsig.org>
>> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
>> ---

> I don't understand this at all.  Yes, FS_XFLAG_CASEFOLD is readonly,
> but how does clearing FS_CASEFOLD_FL from the fileattr_get output
> (without clearing XFLAG_CASEFOLD!) solve anything?  This makes the
> reported output inconsistent between fsgetxattr and getflags -- one
> reports case folding, the other reports no casefolding.

The masking is a misplaced reaction to a sashiko review on the
v9 predecessor of this patch [1], which pointed out that v9 set
FS_XFLAG_CASEFOLD in fa->fsx_xflags after xfs_fill_fsxattr() had
already synced fa->flags, leaving the two views inconsistent in
the other direction, and that bulkstat would miss the flag for
the same reason. Moving the injection into xfs_ip2xflags() fixed
both gaps -- but it also surfaced FS_CASEFOLD_FL on the legacy
view, so chattr's RMW through FS_IOC_SETFLAGS hits the EOPNOTSUPP
gate at the top of xfs_fileattr_set(). Hiding it from getflags
was the wrong place to address that.

> If you want to avoid fileattr_set returning EINVAL when setting
> attributes due to the casefold flag, then don't you want to check
> the flag state vs. xfs_has_asciici() in the *fileattr_set* path?

Yep. For v12 I’ll drop the fa->flags mask and add FS_CASEFOLD_FL
to the allowlist in xfs_fileattr_set(), gated on xfs_has_asciici(mp).
xfs_flags2diflags() already has no clause for CASEFOLD, so the
FSSETXATTR path silently no-ops it the same way it does for
FS_XFLAG_HASATTR, and FS_XFLAG_CASEFOLD is in FS_XFLAG_RDONLY_MASK
so FSSETXATTR strips it centrally. Both views then agree, and a
chattr round-trip is accepted as a no-op.

The hfsplus patch in this series carries the same pattern --
FS_XFLAG_CASEFOLD is set after fileattr_fill_flags() so that
FS_CASEFOLD_FL stays out of fa->flags and dodges the EOPNOTSUPP
gate in hfsplus_fileattr_set(). I will fix it the same way.

Thanks for the catch!

[1] https://sashiko.dev/#/patchset/20260422-case-sensitivity-v9-0-be023cc070e2@oracle.com?part=9


-- 
Chuck Lever