linux-ext4 - [PATCH v5 01/16] fs: Add case sensitivity info to file

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Message-ID: <20260116144616.2098618-2-cel@kernel.org>
Date: Fri, 16 Jan 2026 09:46:00 -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,
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	senozhatsky@...omium.org,
	Chuck Lever <chuck.lever@...cle.com>
Subject: [PATCH v5 01/16] fs: Add case sensitivity info 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 case_insensitive and
case_nonpreserving boolean fields to struct file_kattr.

The case_insensitive and case_nonpreserving fields in struct
file_kattr default to false (POSIX semantics: case-sensitive and
case-preserving), allowing filesystems to set them only when
behavior differs from the default.

Case sensitivity information is exported to userspace via the
existing fa_xflags field using the new FS_XFLAG_CASEFOLD and
FS_XFLAG_CASENONPRESERVING flags.

Signed-off-by: Chuck Lever <chuck.lever@...cle.com>
---
 fs/file_attr.c           | 6 ++++++
 include/linux/fileattr.h | 6 +++++-
 include/uapi/linux/fs.h  | 2 ++
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/fs/file_attr.c b/fs/file_attr.c
index 13cdb31a3e94..2f83f3c6a170 100644
--- a/fs/file_attr.c
+++ b/fs/file_attr.c
@@ -84,6 +84,8 @@ int vfs_fileattr_get(struct dentry *dentry, struct file_kattr *fa)
 	struct inode *inode = d_inode(dentry);
 	int error;
 
+	memset(fa, 0, sizeof(*fa));
+
 	if (!inode->i_op->fileattr_get)
 		return -ENOIOCTLCMD;
 
@@ -106,6 +108,10 @@ static void fileattr_to_file_attr(const struct file_kattr *fa,
 	fattr->fa_nextents = fa->fsx_nextents;
 	fattr->fa_projid = fa->fsx_projid;
 	fattr->fa_cowextsize = fa->fsx_cowextsize;
+	if (fa->case_insensitive)
+		fattr->fa_xflags |= FS_XFLAG_CASEFOLD;
+	if (fa->case_nonpreserving)
+		fattr->fa_xflags |= FS_XFLAG_CASENONPRESERVING;
 }
 
 /**
diff --git a/include/linux/fileattr.h b/include/linux/fileattr.h
index f89dcfad3f8f..7f2e557255ce 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 \
@@ -51,6 +52,9 @@ struct file_kattr {
 	/* selectors: */
 	bool	flags_valid:1;
 	bool	fsx_valid:1;
+	/* case sensitivity behavior: */
+	bool	case_insensitive:1;
+	bool	case_nonpreserving:1;
 };
 
 int copy_fsxattr_to_user(const struct file_kattr *fa, struct fsxattr __user *ufa);
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