linux-ext4 - Re: [PATCH v4 01/16] fs: Add case sensitivity info to file

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Message-ID: <20260115-mitgift-crashtest-35039325f65c@brauner>
Date: Thu, 15 Jan 2026 09:29:37 +0100
From: Christian Brauner <brauner@...nel.org>
To: "Darrick J. Wong" <djwong@...nel.org>
Cc: Chuck Lever <cel@...nel.org>, Jan Kara <jack@...e.cz>, 
	vira@...p.suse.de, linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org, 
	linux-xfs@...r.kernel.org, linux-cifs@...r.kernel.org, linux-nfs@...r.kernel.org, 
	linux-f2fs-devel@...ts.sourceforge.net, OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>, 
	Namjae Jeon <linkinjeon@...nel.org>, Sungjong Seo <sj1557.seo@...sung.com>, 
	Yuezhang Mo <yuezhang.mo@...y.com>, almaz.alexandrovich@...agon-software.com, 
	Viacheslav Dubeyko <slava@...eyko.com>, glaubitz@...sik.fu-berlin.de, frank.li@...o.com, 
	Theodore Tso <tytso@....edu>, adilger.kernel@...ger.ca, Carlos Maiolino <cem@...nel.org>, 
	Steve French <sfrench@...ba.org>, Paulo Alcantara <pc@...guebit.org>, 
	Ronnie Sahlberg <ronniesahlberg@...il.com>, Shyam Prasad N <sprasad@...rosoft.com>, 
	Trond Myklebust <trondmy@...nel.org>, Anna Schumaker <anna@...nel.org>, 
	Jaegeuk Kim <jaegeuk@...nel.org>, Chao Yu <chao@...nel.org>, Hans de Goede <hansg@...nel.org>, 
	senozhatsky@...omium.org, Chuck Lever <chuck.lever@...cle.com>
Subject: Re: [PATCH v4 01/16] fs: Add case sensitivity info to file_kattr

On Wed, Jan 14, 2026 at 12:01:30PM -0800, Darrick J. Wong wrote:
> On Wed, Jan 14, 2026 at 02:01:14PM -0500, Chuck Lever wrote:
> > 
> > 
> > On Wed, Jan 14, 2026, at 1:11 PM, Jan Kara wrote:
> > > On Wed 14-01-26 09:28:44, Chuck Lever wrote:
> > >> From: Chuck Lever <chuck.lever@...cle.com>
> > >> 
> > >> Enable upper layers such as NFSD to retrieve case sensitivity
> > >> information from file systems by adding case_insensitive and
> > >> case_nonpreserving boolean fields to struct file_kattr.
> > >> 
> > >> These fields default to false (POSIX semantics: case-sensitive and
> > >> case-preserving), allowing filesystems to set them only when
> > >> behavior differs from the default.
> > >> 
> > >> Signed-off-by: Chuck Lever <chuck.lever@...cle.com>
> > > ...
> > >> diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
> > >> index 66ca526cf786..07286d34b48b 100644
> > >> --- a/include/uapi/linux/fs.h
> > >> +++ b/include/uapi/linux/fs.h
> > >> @@ -229,10 +229,20 @@ struct file_attr {
> > >>  	__u32 fa_nextents;	/* nextents field value (get)   */
> > >>  	__u32 fa_projid;	/* project identifier (get/set) */
> > >>  	__u32 fa_cowextsize;	/* CoW extsize field value (get/set) */
> > >> +	/* VER1 additions: */
> > >> +	__u32 fa_case_behavior;	/* case sensitivity (get) */
> > >> +	__u32 fa_reserved;
> > >>  };
> > >>  
> > >>  #define FILE_ATTR_SIZE_VER0 24
> > >> -#define FILE_ATTR_SIZE_LATEST FILE_ATTR_SIZE_VER0
> > >> +#define FILE_ATTR_SIZE_VER1 32
> > >> +#define FILE_ATTR_SIZE_LATEST FILE_ATTR_SIZE_VER1
> > >> +
> > >> +/*
> > >> + * Case sensitivity flags for fa_case_behavior
> > >> + */
> > >> +#define FS_CASE_INSENSITIVE	0x00000001	/* case-insensitive lookups */
> > >> +#define FS_CASE_NONPRESERVING	0x00000002	/* case not preserved */
> > >
> > > This is a matter of taste so not sure what others think about it but
> > > file_attr already have fa_xflags field and there is already one flag which
> > > doesn't directly correspond to on-disk representation (FS_XFLAG_HASATTR) so
> > > we could also put the two new flags in there... I have hard time imagining
> > > fa_case_behavior would grow past the two flags you've introduced so u32
> > > seems a bit wasteful.
> > 
> > No problem. I'll wait for additional guidance on this.
> 
> Sounds like a better use of space in struct file_attr than adding
> another pair of u32.

Fine by me as well.