Re: [RFC PATCH] fs: Plumb case sensitivity bits into statx

[Chuck Lever <cel@kernel.org>]

On 10/3/25 11:24 AM, Gabriel Krisman Bertazi wrote:
> Amir Goldstein <amir73il@gmail.com> writes:
> 
>> On Thu, Sep 25, 2025 at 5:21 PM Chuck Lever <cel@kernel.org> wrote:

>>> diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
>>> index 1686861aae20..e929b30d64b6 100644
>>> --- a/include/uapi/linux/stat.h
>>> +++ b/include/uapi/linux/stat.h
>>> @@ -219,6 +219,7 @@ struct statx {
>>>  #define STATX_SUBVOL           0x00008000U     /* Want/got stx_subvol */
>>>  #define STATX_WRITE_ATOMIC     0x00010000U     /* Want/got atomic_write_* fields */
>>>  #define STATX_DIO_READ_ALIGN   0x00020000U     /* Want/got dio read alignment info */
>>> +#define STATX_CASE_INFO                0x00040000U     /* Want/got case folding info */
>>>
>>>  #define STATX__RESERVED                0x80000000U     /* Reserved for future struct statx expansion */
>>>
>>> @@ -257,4 +258,18 @@ struct statx {
>>>  #define STATX_ATTR_WRITE_ATOMIC                0x00400000 /* File supports atomic write operations */
>>>
>>>
>>> +/*
>>> + * File system support for case folding is available via a bitmap.
>>> + */
>>> +#define STATX_CASE_PRESERVING          0x80000000 /* File name case is preserved */
>>> +
>>> +/* Values stored in the low-order byte of .case_info */
>>> +enum {
>>> +       statx_case_sensitive = 0,
>>> +       statx_case_ascii,
>>> +       statx_case_utf8,
>>> +       statx_case_utf16,
>>> +};
>>> +#define STATX_CASE_FOLDING_TYPE                0x000000ff
> 
> Does the protocol care about unicode version?  For userspace, it would
> be very relevant to expose it, as well as other details such as
> decomposition type.

For the purposes of indicating case sensitivity and preservation, the
NFS protocol does not currently care about unicode version.

But this is a very flexible proposal right now. Please recommend what
you'd like to see here. I hope I've given enough leeway that a unicode
version could be provided for other API consumers.

(As I mentioned to Jeff, there is no user space statx component in the
current proposal, but it should get one if it is agreed that's useful to
include).

-- 
Chuck Lever