linux-ext4 - [PATCH v8 02/17] fs: Add case sensitivity flags to file

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Message-ID: <20260217214741.1928576-3-cel@kernel.org>
Date: Tue, 17 Feb 2026 16:47:26 -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,
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	linux-f2fs-devel@...ts.sourceforge.net,
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	jaegeuk@...nel.org,
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	hansg@...nel.org,
	senozhatsky@...omium.org,
	Chuck Lever <chuck.lever@...cle.com>,
	"Darrick J. Wong" <djwong@...nel.org>
Subject: [PATCH v8 02/17] fs: Add case sensitivity flags to file_kattr

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.

Case sensitivity information is exported to userspace via the
fa_xflags field in the FS_IOC_FSGETXATTR ioctl and file_getattr()
system call.

Reviewed-by: "Darrick J. Wong" <djwong@...nel.org>
Signed-off-by: Chuck Lever <chuck.lever@...cle.com>
---
 fs/file_attr.c           | 4 ++++
 include/linux/fileattr.h | 3 ++-
 include/uapi/linux/fs.h  | 7 +++++++
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/fs/file_attr.c b/fs/file_attr.c
index 42aa511111a0..5d9a7ed159fb 100644
--- a/fs/file_attr.c
+++ b/fs/file_attr.c
@@ -37,6 +37,8 @@ void fileattr_fill_xflags(struct file_kattr *fa, u32 xflags)
 		fa->flags |= FS_PROJINHERIT_FL;
 	if (fa->fsx_xflags & FS_XFLAG_VERITY)
 		fa->flags |= FS_VERITY_FL;
+	if (fa->fsx_xflags & FS_XFLAG_CASEFOLD)
+		fa->flags |= FS_CASEFOLD_FL;
 }
 EXPORT_SYMBOL(fileattr_fill_xflags);
 
@@ -67,6 +69,8 @@ void fileattr_fill_flags(struct file_kattr *fa, u32 flags)
 		fa->fsx_xflags |= FS_XFLAG_PROJINHERIT;
 	if (fa->flags & FS_VERITY_FL)
 		fa->fsx_xflags |= FS_XFLAG_VERITY;
+	if (fa->flags & FS_CASEFOLD_FL)
+		fa->fsx_xflags |= FS_XFLAG_CASEFOLD;
 }
 EXPORT_SYMBOL(fileattr_fill_flags);
 
diff --git a/include/linux/fileattr.h b/include/linux/fileattr.h
index 3780904a63a6..58044b598016 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_VERITY)
+	(FS_XFLAG_PREALLOC | FS_XFLAG_HASATTR | FS_XFLAG_VERITY | \
+	 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 70b2b661f42c..2fa003575e8b 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -254,6 +254,13 @@ struct file_attr {
 #define FS_XFLAG_DAX		0x00008000	/* use DAX for IO */
 #define FS_XFLAG_COWEXTSIZE	0x00010000	/* CoW extent size allocator hint */
 #define FS_XFLAG_VERITY		0x00020000	/* fs-verity enabled */
+/*
+ * Case handling flags (read-only, cannot be set via ioctl).
+ * Default (neither set) indicates POSIX semantics: case-sensitive
+ * lookups and case-preserving storage.
+ */
+#define FS_XFLAG_CASEFOLD	0x00040000	/* case-insensitive lookups */
+#define FS_XFLAG_CASENONPRESERVING 0x00080000	/* 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
-- 
2.53.0