linux-ext4 - [PATCH v5 02/16] fat: Implement fileattr

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Message-ID: <20260116144616.2098618-3-cel@kernel.org>
Date: Fri, 16 Jan 2026 09:46:01 -0500
From: Chuck Lever <cel@...nel.org>
To: Al Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>,
	Jan Kara <jack@...e.cz>
Cc: <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,
	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: [PATCH v5 02/16] fat: Implement fileattr_get for case sensitivity

From: Chuck Lever <chuck.lever@...cle.com>

Report FAT's case sensitivity behavior via the file_kattr boolean
fields. FAT filesystems are case-insensitive by default.

MSDOS supports a 'nocase' mount option that enables case-sensitive
behavior; check this option when reporting case sensitivity.

VFAT long filename entries preserve case; without VFAT, only
uppercased 8.3 short names are stored. MSDOS with 'nocase' also
preserves case since the name-formatting code skips upcasing when
'nocase' is set. Check both options when reporting case preservation.

Signed-off-by: Chuck Lever <chuck.lever@...cle.com>
---
 fs/fat/fat.h         |  3 +++
 fs/fat/file.c        | 20 ++++++++++++++++++++
 fs/fat/namei_msdos.c |  1 +
 fs/fat/namei_vfat.c  |  1 +
 4 files changed, 25 insertions(+)

diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index d3e426de5f01..9e208eeb46c4 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);
+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..328f9e3c9fa3 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 +396,24 @@ 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 msdos_sb_info *sbi = MSDOS_SB(dentry->d_sb);
+
+	/*
+	 * FAT filesystems are case-insensitive by default. MSDOS
+	 * supports a 'nocase' mount option for case-sensitive behavior.
+	 *
+	 * VFAT long filename entries preserve case. Without VFAT, only
+	 * uppercased 8.3 short names are stored. MSDOS with 'nocase'
+	 * also preserves case.
+	 */
+	fa->case_insensitive = !sbi->options.nocase;
+	fa->case_nonpreserving = !sbi->options.isvfat && !sbi->options.nocase;
+	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 +593,6 @@ 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,
 };
 
-- 
2.52.0