Re: [PATCH v11 00/15] Exposing case folding behavior

Jan Kara
2026-04-27T15:30:56Z

On Mon 27-04-26 09:30:28, Chuck Lever wrote:
>
> On Mon, Apr 27, 2026, at 6:55 AM, Jan Kara wrote:
> > On Fri 24-04-26 21:53:02, Chuck Lever wrote:
> >> Changes since v10:
> >> - cifs: Source case-handling flags from the server's cached
> >> FS_ATTRIBUTE_INFORMATION reply instead of the nocase mount
> >> option, with a nocase fallback when the reply is absent
> >> - Address findings from sashiko(gemini-3) and gpt-5.5:
> >> - nfs: Skip pathconf case bits on NFSv4 (set via FATTR4_CASE_*
> >> instead)
> >> - xfs: Hide FS_CASEFOLD_FL from the legacy flags view so
> >> chattr round-trips do not hit the setflags whitelist
> >> - ext4, f2fs: Drop redundant fileattr_get patches; the
> >> FS_CASEFOLD_FL translation in fileattr_fill_flags() already
> >> reports FS_XFLAG_CASEFOLD for casefolded directories
> >
> > Err, how is this supposed to work? I wasn't able to find any code
> > transforming S_CASEFOLDED inode flag into FS_CASEFOLD_FL on fileattr_get
> > path. Sure, fileattr_fill_flags() takes care of setting FS_XFLAG_CASEFOLD
> > once FS_CASEFOLD_FL is set. What am I missing?
>
> Agreed, that is a little surprising.
>
> The path does not go through S_CASEFOLD. Both filesystems
> report FS_CASEFOLD_FL straight from their on-disk flag word.
>
> For ext4, EXT4_CASEFOLD_FL is 0x40000000, the same bit value
> as FS_CASEFOLD_FL, and it is included in EXT4_FL_USER_VISIBLE.
> ext4_iget() loads it into ei->i_flags directly from
> raw_inode->i_flags (fs/ext4/inode.c:5358). ext4_fileattr_get()
> then masks with EXT4_FL_USER_VISIBLE and hands the result to
> fileattr_fill_flags(), which translates FS_CASEFOLD_FL into
> FS_XFLAG_CASEFOLD on the way out.

Oh, right. I've missed how EXT4_CASEFOLD_FL propagates into FS_CASEFOLD_FL.
Thanks for clearing that out.

Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR