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). f2fs always preserves case
at rest.

Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Chuck Lever <redacted>
---
 fs/f2fs/file.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index fb12c5c9affd..347568ff0d58 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c

@@ -3463,6 +3463,14 @@ 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);
 
+	/*
+	 * Casefold is a per-directory attribute in f2fs; the on-disk
+	 * name is preserved regardless. Report FS_XFLAG_CASEFOLD for
+	 * casefolded directories so callers (e.g. NFS export) can
+	 * advertise case-insensitive lookup semantics for that tree.
+	 */
+	if (IS_CASEFOLDED(inode))
+		fa->fsx_xflags |= FS_XFLAG_CASEFOLD;
 	return 0;
 }
 

-- 
2.53.0