From: Chuck Lever <redacted>

NFS and other remote filesystem protocols need to determine
whether a local filesystem performs case-insensitive lookups
so they can provide correct semantics to clients. Without
this information, f2fs exports cannot properly advertise
their filename case behavior.

Report f2fs case sensitivity behavior via the FS_XFLAG_CASEFOLD
flag. Like ext4, f2fs supports per-directory case folding via
the casefold flag (IS_CASEFOLDED). Files are always case-preserving.

Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Chuck Lever <redacted>
---
 fs/f2fs/file.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index c8a2f17a8f11..f7f616e041dc 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c

@@ -3453,6 +3453,13 @@ int f2fs_fileattr_get(struct dentry *dentry, struct file_kattr *fa)
 	if (f2fs_sb_has_project_quota(F2FS_I_SB(inode)))
 		fa->fsx_projid = from_kprojid(&init_user_ns, fi->i_projid);
 
+	/*
+	 * f2fs preserves case (the default). If this inode is a
+	 * casefolded directory, report case-insensitive; otherwise
+	 * report case-sensitive (standard POSIX behavior).
+	 */
+	if (IS_CASEFOLDED(inode))
+		fa->fsx_xflags |= FS_XFLAG_CASEFOLD;
 	return 0;
 }
 

-- 
2.53.0