linux-ext4 - Re: [PATCH v7 01/16] fs: Add case sensitivity flags to file

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Message-ID: <20260123002646.GL5945@frogsfrogsfrogs>
Date: Thu, 22 Jan 2026 16:26:46 -0800
From: "Darrick J. Wong" <djwong@...nel.org>
To: Chuck Lever <cel@...nel.org>
Cc: Al Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
	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-api@...r.kernel.org,
	linux-f2fs-devel@...ts.sourceforge.net, hirofumi@...l.parknet.co.jp,
	linkinjeon@...nel.org, sj1557.seo@...sung.com, yuezhang.mo@...y.com,
	almaz.alexandrovich@...agon-software.com, slava@...eyko.com,
	glaubitz@...sik.fu-berlin.de, frank.li@...o.com, tytso@....edu,
	adilger.kernel@...ger.ca, cem@...nel.org, sfrench@...ba.org,
	pc@...guebit.org, ronniesahlberg@...il.com, sprasad@...rosoft.com,
	trondmy@...nel.org, anna@...nel.org, jaegeuk@...nel.org,
	chao@...nel.org, hansg@...nel.org, senozhatsky@...omium.org,
	Chuck Lever <chuck.lever@...cle.com>
Subject: Re: [PATCH v7 01/16] fs: Add case sensitivity flags to file_kattr

On Thu, Jan 22, 2026 at 11:02:56AM -0500, 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 FS_XFLAG_CASEFOLD and
> FS_XFLAG_CASENONPRESERVING flags.
> 
> Filesystems report case-insensitive or case-nonpreserving behavior
> by setting these flags directly in fa->fsx_xflags. The default
> (flags unset) indicates POSIX semantics: case-sensitive and
> case-preserving. These flags are read-only; userspace cannot set
> them via ioctl.
> 
> Remove struct file_kattr initialization from fileattr_fill_xflags()
> and fileattr_fill_flags(). Callers at ioctl/syscall entry points
> zero-initialize the struct themselves, which allows them to pass
> hints (flags_valid, fsx_valid) to the filesystem's ->fileattr_get()
> callback via the fa argument. Filesystem handlers that invoke these
> fill functions can now set flags directly in fa->fsx_xflags before
> calling them, without the fill functions zeroing those values.

In hindsight I regret not asking for the file_kattr initialization
change to be in a separate patch.

> Case sensitivity information is exported to userspace via the
> fa_xflags field in the FS_IOC_FSGETXATTR ioctl and file_getattr()
> system call.
> 
> Signed-off-by: Chuck Lever <chuck.lever@...cle.com>

The UAPI changes still look ok to me.  AFAICT the file_kattr
initialization now seem like they don't zap fields to confuse
vfs_fileattr_get.

Reviewed-by: "Darrick J. Wong" <djwong@...nel.org>

--D

> ---
>  fs/file_attr.c           | 12 ++++--------
>  fs/xfs/xfs_ioctl.c       |  2 +-
>  include/linux/fileattr.h |  3 ++-
>  include/uapi/linux/fs.h  |  2 ++
>  4 files changed, 9 insertions(+), 10 deletions(-)
> 
> diff --git a/fs/file_attr.c b/fs/file_attr.c
> index 13cdb31a3e94..6e37040fc5fa 100644
> --- a/fs/file_attr.c
> +++ b/fs/file_attr.c
> @@ -15,12 +15,10 @@
>   * @fa:		fileattr pointer
>   * @xflags:	FS_XFLAG_* flags
>   *
> - * Set ->fsx_xflags, ->fsx_valid and ->flags (translated xflags).  All
> - * other fields are zeroed.
> + * Set ->fsx_xflags, ->fsx_valid and ->flags (translated xflags).
>   */
>  void fileattr_fill_xflags(struct file_kattr *fa, u32 xflags)
>  {
> -	memset(fa, 0, sizeof(*fa));
>  	fa->fsx_valid = true;
>  	fa->fsx_xflags = xflags;
>  	if (fa->fsx_xflags & FS_XFLAG_IMMUTABLE)
> @@ -46,11 +44,9 @@ EXPORT_SYMBOL(fileattr_fill_xflags);
>   * @flags:	FS_*_FL flags
>   *
>   * Set ->flags, ->flags_valid and ->fsx_xflags (translated flags).
> - * All other fields are zeroed.
>   */
>  void fileattr_fill_flags(struct file_kattr *fa, u32 flags)
>  {
> -	memset(fa, 0, sizeof(*fa));
>  	fa->flags_valid = true;
>  	fa->flags = flags;
>  	if (fa->flags & FS_SYNC_FL)
> @@ -323,7 +319,7 @@ int ioctl_setflags(struct file *file, unsigned int __user *argp)
>  {
>  	struct mnt_idmap *idmap = file_mnt_idmap(file);
>  	struct dentry *dentry = file->f_path.dentry;
> -	struct file_kattr fa;
> +	struct file_kattr fa = {};
>  	unsigned int flags;
>  	int err;
>  
> @@ -355,7 +351,7 @@ int ioctl_fssetxattr(struct file *file, void __user *argp)
>  {
>  	struct mnt_idmap *idmap = file_mnt_idmap(file);
>  	struct dentry *dentry = file->f_path.dentry;
> -	struct file_kattr fa;
> +	struct file_kattr fa = {};
>  	int err;
>  
>  	err = copy_fsxattr_from_user(&fa, argp);
> @@ -434,7 +430,7 @@ SYSCALL_DEFINE5(file_setattr, int, dfd, const char __user *, filename,
>  	struct filename *name __free(putname) = NULL;
>  	unsigned int lookup_flags = 0;
>  	struct file_attr fattr;
> -	struct file_kattr fa;
> +	struct file_kattr fa = {};
>  	int error;
>  
>  	BUILD_BUG_ON(sizeof(struct file_attr) < FILE_ATTR_SIZE_VER0);
> diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> index 59eaad774371..f0417c4d1fca 100644
> --- a/fs/xfs/xfs_ioctl.c
> +++ b/fs/xfs/xfs_ioctl.c
> @@ -496,7 +496,7 @@ xfs_ioc_fsgetxattra(
>  	xfs_inode_t		*ip,
>  	void			__user *arg)
>  {
> -	struct file_kattr	fa;
> +	struct file_kattr	fa = {};
>  
>  	xfs_ilock(ip, XFS_ILOCK_SHARED);
>  	xfs_fill_fsxattr(ip, XFS_ATTR_FORK, &fa);
> diff --git a/include/linux/fileattr.h b/include/linux/fileattr.h
> index f89dcfad3f8f..709de829659f 100644
> --- a/include/linux/fileattr.h
> +++ b/include/linux/fileattr.h
> @@ -16,7 +16,8 @@
>  
>  /* Read-only inode flags */
>  #define FS_XFLAG_RDONLY_MASK \
> -	(FS_XFLAG_PREALLOC | FS_XFLAG_HASATTR)
> +	(FS_XFLAG_PREALLOC | FS_XFLAG_HASATTR | \
> +	 FS_XFLAG_CASEFOLD | FS_XFLAG_CASENONPRESERVING)
>  
>  /* Flags to indicate valid value of fsx_ fields */
>  #define FS_XFLAG_VALUES_MASK \
> diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
> index 66ca526cf786..919148beaa8c 100644
> --- a/include/uapi/linux/fs.h
> +++ b/include/uapi/linux/fs.h
> @@ -253,6 +253,8 @@ struct file_attr {
>  #define FS_XFLAG_FILESTREAM	0x00004000	/* use filestream allocator */
>  #define FS_XFLAG_DAX		0x00008000	/* use DAX for IO */
>  #define FS_XFLAG_COWEXTSIZE	0x00010000	/* CoW extent size allocator hint */
> +#define FS_XFLAG_CASEFOLD	0x00020000	/* case-insensitive lookups */
> +#define FS_XFLAG_CASENONPRESERVING 0x00040000	/* case not preserved */
>  #define FS_XFLAG_HASATTR	0x80000000	/* no DIFLAG for this	*/
>  
>  /* the read-only stuff doesn't really belong here, but any other place is
> -- 
> 2.52.0
> 
>