linux-ext4 - [PATCH v4 01/16] fs: Add case sensitivity info to file

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Message-ID: <20260114142900.3945054-2-cel@kernel.org>
Date: Wed, 14 Jan 2026 09:28:44 -0500
From: Chuck Lever <cel@...nel.org>
To: vira@....codeaurora.org, 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,
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	slava@...eyko.com,
	glaubitz@...sik.fu-berlin.de,
	frank.li@...o.com,
	tytso@....edu,
	adilger.kernel@...ger.ca,
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	chao@...nel.org,
	hansg@...nel.org,
	senozhatsky@...omium.org,
	Chuck Lever <chuck.lever@...cle.com>
Subject: [PATCH v4 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.

These fields default to false (POSIX semantics: case-sensitive and
case-preserving), allowing filesystems to set them only when
behavior differs from the default.

Signed-off-by: Chuck Lever <chuck.lever@...cle.com>
---
 fs/file_attr.c           | 14 ++++++++++++++
 include/linux/fileattr.h |  3 +++
 include/uapi/linux/fs.h  | 12 +++++++++++-
 3 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/fs/file_attr.c b/fs/file_attr.c
index 13cdb31a3e94..df4b2fc68532 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_case_behavior |= FS_CASE_INSENSITIVE;
+	if (fa->case_nonpreserving)
+		fattr->fa_case_behavior |= FS_CASE_NONPRESERVING;
 }
 
 /**
@@ -382,6 +388,10 @@ SYSCALL_DEFINE5(file_getattr, int, dfd, const char __user *, filename,
 
 	BUILD_BUG_ON(sizeof(struct file_attr) < FILE_ATTR_SIZE_VER0);
 	BUILD_BUG_ON(sizeof(struct file_attr) != FILE_ATTR_SIZE_LATEST);
+	BUILD_BUG_ON(offsetofend(struct file_attr, fa_cowextsize) !=
+		     FILE_ATTR_SIZE_VER0);
+	BUILD_BUG_ON(offsetofend(struct file_attr, fa_reserved) !=
+		     FILE_ATTR_SIZE_VER1);
 
 	if ((at_flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
 		return -EINVAL;
@@ -439,6 +449,10 @@ SYSCALL_DEFINE5(file_setattr, int, dfd, const char __user *, filename,
 
 	BUILD_BUG_ON(sizeof(struct file_attr) < FILE_ATTR_SIZE_VER0);
 	BUILD_BUG_ON(sizeof(struct file_attr) != FILE_ATTR_SIZE_LATEST);
+	BUILD_BUG_ON(offsetofend(struct file_attr, fa_cowextsize) !=
+		     FILE_ATTR_SIZE_VER0);
+	BUILD_BUG_ON(offsetofend(struct file_attr, fa_reserved) !=
+		     FILE_ATTR_SIZE_VER1);
 
 	if ((at_flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
 		return -EINVAL;
diff --git a/include/linux/fileattr.h b/include/linux/fileattr.h
index f89dcfad3f8f..086f28b90734 100644
--- a/include/linux/fileattr.h
+++ b/include/linux/fileattr.h
@@ -51,6 +51,9 @@ 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..07286d34b48b 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -229,10 +229,20 @@ struct file_attr {
 	__u32 fa_nextents;	/* nextents field value (get)   */
 	__u32 fa_projid;	/* project identifier (get/set) */
 	__u32 fa_cowextsize;	/* CoW extsize field value (get/set) */
+	/* VER1 additions: */
+	__u32 fa_case_behavior;	/* case sensitivity (get) */
+	__u32 fa_reserved;
 };
 
 #define FILE_ATTR_SIZE_VER0 24
-#define FILE_ATTR_SIZE_LATEST FILE_ATTR_SIZE_VER0
+#define FILE_ATTR_SIZE_VER1 32
+#define FILE_ATTR_SIZE_LATEST FILE_ATTR_SIZE_VER1
+
+/*
+ * Case sensitivity flags for fa_case_behavior
+ */
+#define FS_CASE_INSENSITIVE	0x00000001	/* case-insensitive lookups */
+#define FS_CASE_NONPRESERVING	0x00000002	/* case not preserved */
 
 /*
  * Flags for the fsx_xflags field
-- 
2.52.0