From: Chuck Lever <chuck.lever@oracle.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.

Relocate struct file_kattr initialization from fileattr_fill_xflags()
and fileattr_fill_flags() to vfs_fileattr_get() and the ioctl/syscall
call sites. This allows filesystem ->fileattr_get() callbacks to set
flags directly in fa->fsx_xflags before invoking the fill functions,
which previously would have zeroed those values. Callers that bypass
vfs_fileattr_get() must now zero-initialize the struct themselves.

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

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 fs/file_attr.c           | 14 ++++++--------
 fs/xfs/xfs_ioctl.c       |  2 +-
 include/linux/fileattr.h |  3 ++-
 include/uapi/linux/fs.h  |  2 ++
 4 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/fs/file_attr.c b/fs/file_attr.c
index 13cdb31a3e94..2700200c5b9c 100644
--- a/fs/file_attr.c
+++ b/fs/file_attr.c
@@ -15,12 +15,10 @@
  * @fa:		fileattr pointer
  * @xflags:	FS_XFLAG_* flags
  *
- * Set ->fsx_xflags, ->fsx_valid and ->flags (translated xflags).  All
- * other fields are zeroed.
+ * Set ->fsx_xflags, ->fsx_valid and ->flags (translated xflags).
  */
 void fileattr_fill_xflags(struct file_kattr *fa, u32 xflags)
 {
-	memset(fa, 0, sizeof(*fa));
 	fa->fsx_valid = true;
 	fa->fsx_xflags = xflags;
 	if (fa->fsx_xflags & FS_XFLAG_IMMUTABLE)
@@ -46,11 +44,9 @@ EXPORT_SYMBOL(fileattr_fill_xflags);
  * @flags:	FS_*_FL flags
  *
  * Set ->flags, ->flags_valid and ->fsx_xflags (translated flags).
- * All other fields are zeroed.
  */
 void fileattr_fill_flags(struct file_kattr *fa, u32 flags)
 {
-	memset(fa, 0, sizeof(*fa));
 	fa->flags_valid = true;
 	fa->flags = flags;
 	if (fa->flags & FS_SYNC_FL)
@@ -84,6 +80,8 @@ 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;
 
@@ -323,7 +321,7 @@ int ioctl_setflags(struct file *file, unsigned int __user *argp)
 {
 	struct mnt_idmap *idmap = file_mnt_idmap(file);
 	struct dentry *dentry = file->f_path.dentry;
-	struct file_kattr fa;
+	struct file_kattr fa = {};
 	unsigned int flags;
 	int err;
 
@@ -355,7 +353,7 @@ int ioctl_fssetxattr(struct file *file, void __user *argp)
 {
 	struct mnt_idmap *idmap = file_mnt_idmap(file);
 	struct dentry *dentry = file->f_path.dentry;
-	struct file_kattr fa;
+	struct file_kattr fa = {};
 	int err;
 
 	err = copy_fsxattr_from_user(&fa, argp);
@@ -434,7 +432,7 @@ SYSCALL_DEFINE5(file_setattr, int, dfd, const char __user *, filename,
 	struct filename *name __free(putname) = NULL;
 	unsigned int lookup_flags = 0;
 	struct file_attr fattr;
-	struct file_kattr fa;
+	struct file_kattr fa = {};
 	int error;
 
 	BUILD_BUG_ON(sizeof(struct file_attr) < FILE_ATTR_SIZE_VER0);
diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index 59eaad774371..f0417c4d1fca 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -496,7 +496,7 @@ xfs_ioc_fsgetxattra(
 	xfs_inode_t		*ip,
 	void			__user *arg)
 {
-	struct file_kattr	fa;
+	struct file_kattr	fa = {};
 
 	xfs_ilock(ip, XFS_ILOCK_SHARED);
 	xfs_fill_fsxattr(ip, XFS_ATTR_FORK, &fa);
diff --git a/include/linux/fileattr.h b/include/linux/fileattr.h
index f89dcfad3f8f..709de829659f 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 \
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