linux-kernel - Re: [PATCH v2 2/6] fat: Implement fileattr

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Message-ID: <87v7icl3a7.fsf@mail.parknet.co.jp>
Date: Fri, 12 Dec 2025 13:42:08 +0900
From: OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
To: Chuck Lever <cel@...nel.org>
Cc: Al Viro <viro@...iv.linux.org.uk>, Christian Brauner
 <brauner@...nel.org>,
        <linux-fsdevel@...r.kernel.org>, linux-ext4@...r.kernel.org,
        <linux-nfs@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        almaz.alexandrovich@...agon-software.com, tytso@....edu,
        adilger.kernel@...ger.ca, Volker.Lendecke@...net.de,
        Chuck Lever
 <chuck.lever@...cle.com>
Subject: Re: [PATCH v2 2/6] fat: Implement fileattr_get for case sensitivity

Chuck Lever <cel@...nel.org> writes:

> From: Chuck Lever <chuck.lever@...cle.com>
>
> Report FAT's case sensitivity behavior via the new file_kattr
> case_info field. FAT filesystems are case-insensitive and do not
> preserve case at rest (stored names are uppercased).
>
> The case folding type depends on the mount options: when utf8 is
> enabled, Unicode case folding is used; otherwise ASCII case folding.
>
> Signed-off-by: Chuck Lever <chuck.lever@...cle.com>

I can't see the who and how to use this though, in msdos case, looks
like this should check "nocase" option.

Thanks.

> ---
>  fs/fat/fat.h         |  3 +++
>  fs/fat/file.c        | 18 ++++++++++++++++++
>  fs/fat/namei_msdos.c |  1 +
>  fs/fat/namei_vfat.c  |  1 +
>  4 files changed, 23 insertions(+)
>
> diff --git a/fs/fat/fat.h b/fs/fat/fat.h
> index d3e426de5f01..38da08d8fec4 100644
> --- a/fs/fat/fat.h
> +++ b/fs/fat/fat.h
> @@ -10,6 +10,8 @@
>  #include <linux/fs_context.h>
>  #include <linux/fs_parser.h>
>  
> +struct file_kattr;
> +
>  /*
>   * vfat shortname flags
>   */
> @@ -407,6 +409,7 @@ extern void fat_truncate_blocks(struct inode *inode, loff_t offset);
>  extern int fat_getattr(struct mnt_idmap *idmap,
>  		       const struct path *path, struct kstat *stat,
>  		       u32 request_mask, unsigned int flags);
> +extern int fat_fileattr_get(struct dentry *dentry, struct file_kattr *fa);
>  extern int fat_file_fsync(struct file *file, loff_t start, loff_t end,
>  			  int datasync);
>  
> diff --git a/fs/fat/file.c b/fs/fat/file.c
> index 4fc49a614fb8..123f4c1efdf4 100644
> --- a/fs/fat/file.c
> +++ b/fs/fat/file.c
> @@ -16,6 +16,7 @@
>  #include <linux/fsnotify.h>
>  #include <linux/security.h>
>  #include <linux/falloc.h>
> +#include <linux/fileattr.h>
>  #include "fat.h"
>  
>  static long fat_fallocate(struct file *file, int mode,
> @@ -395,6 +396,22 @@ void fat_truncate_blocks(struct inode *inode, loff_t offset)
>  	fat_flush_inodes(inode->i_sb, inode, NULL);
>  }
>  
> +int fat_fileattr_get(struct dentry *dentry, struct file_kattr *fa)
> +{
> +	struct inode *inode = d_inode(dentry);
> +	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
> +
> +	/*
> +	 * FAT filesystems do not preserve case: stored names are
> +	 * uppercased. They are case-insensitive, using either ASCII
> +	 * or Unicode comparison depending on mount options.
> +	 */
> +	fa->case_info = sbi->options.utf8 ?
> +		FILEATTR_CASEFOLD_UNICODE : FILEATTR_CASEFOLD_ASCII;
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(fat_fileattr_get);
> +
>  int fat_getattr(struct mnt_idmap *idmap, const struct path *path,
>  		struct kstat *stat, u32 request_mask, unsigned int flags)
>  {
> @@ -574,5 +591,6 @@ EXPORT_SYMBOL_GPL(fat_setattr);
>  const struct inode_operations fat_file_inode_operations = {
>  	.setattr	= fat_setattr,
>  	.getattr	= fat_getattr,
> +	.fileattr_get	= fat_fileattr_get,
>  	.update_time	= fat_update_time,
>  };
> diff --git a/fs/fat/namei_msdos.c b/fs/fat/namei_msdos.c
> index 0b920ee40a7f..380add5c6c66 100644
> --- a/fs/fat/namei_msdos.c
> +++ b/fs/fat/namei_msdos.c
> @@ -640,6 +640,7 @@ static const struct inode_operations msdos_dir_inode_operations = {
>  	.rename		= msdos_rename,
>  	.setattr	= fat_setattr,
>  	.getattr	= fat_getattr,
> +	.fileattr_get	= fat_fileattr_get,
>  	.update_time	= fat_update_time,
>  };
>  
> diff --git a/fs/fat/namei_vfat.c b/fs/fat/namei_vfat.c
> index 5dbc4cbb8fce..6cf513f97afa 100644
> --- a/fs/fat/namei_vfat.c
> +++ b/fs/fat/namei_vfat.c
> @@ -1180,6 +1180,7 @@ static const struct inode_operations vfat_dir_inode_operations = {
>  	.rename		= vfat_rename2,
>  	.setattr	= fat_setattr,
>  	.getattr	= fat_getattr,
> +	.fileattr_get	= fat_fileattr_get,
>  	.update_time	= fat_update_time,
>  };

-- 
OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>