[PATCH v2 02/23] xfs: Report case sensitivity in fileattr_get

[Andrey Albershteyn <aalbersh@kernel.org>]

From: Chuck Lever <cel@kernel.org>

Source kernel commit: c9da43e4e5c32c2cb318e616ffa48c7148a70d49

Upper layers such as NFSD need to query whether a filesystem
is case-sensitive. Add FS_XFLAG_CASEFOLD to xfs_ip2xflags()
when the filesystem is formatted with the ASCIICI feature
flag. This serves both FS_IOC_FSGETXATTR (via xfs_fill_fsxattr()
in xfs_fileattr_get()) and XFS_IOC_BULKSTAT (which populates
bs_xflags directly from xfs_ip2xflags()), so bulkstat consumers
and per-inode queries see a consistent view of the filesystem's
case-folding behavior.

FS_XFLAG_CASEFOLD is read-only: FS_XFLAG_RDONLY_MASK ensures
FS_IOC_FSSETXATTR strips it, and xfs_flags2diflags() has no
clause for CASEFOLD so the on-disk diflags are unaffected.
The legacy FS_IOC_SETFLAGS path in xfs_fileattr_set() also
allows FS_CASEFOLD_FL through its allowlist on ASCIICI
filesystems so that a chattr read-modify-write cycle does
not fail with EOPNOTSUPP.

XFS always preserves case. XFS is case-sensitive by default,
but supports ASCII case-insensitive lookups when formatted
with the ASCIICI feature flag.

Reviewed-by: Roland Mainz <roland.mainz@nrubsig.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Link: https://patch.msgid.link/20260507-case-sensitivity-v14-8-e62cc8200435@oracle.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
[djwong: add some missing FS_XFLAG_ private definitions]
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 include/linux.h         | 17 +++++++++++++++++
 libxfs/xfs_inode_util.c |  2 ++
 2 files changed, 19 insertions(+)

diff --git a/include/linux.h b/include/linux.h
index 8972c9596c75..a10d531cffdb 100644
--- a/include/linux.h
+++ b/include/linux.h
@@ -258,6 +258,23 @@ struct file_attr {
 #define FS_XFLAG_COWEXTSIZE	0x00010000	/* CoW extent size allocator hint */
 #endif
 
+#ifndef FS_XFLAG_VERITY
+#define FS_XFLAG_VERITY		0x00020000	/* fs-verity enabled */
+#endif
+
+/*
+ * Case handling flags (read-only, cannot be set via ioctl).
+ * Default (neither set) indicates POSIX semantics: case-sensitive
+ * lookups and case-preserving storage.
+ */
+#ifndef FS_XFLAG_CASEFOLD
+#define FS_XFLAG_CASEFOLD	0x00040000	/* case-insensitive lookups */
+#endif
+
+#ifndef FS_XFLAG_CASENONPRESERVING
+#define FS_XFLAG_CASENONPRESERVING 0x00080000	/* case not preserved */
+#endif
+
 /* Atomic Write */
 #ifndef RWF_ATOMIC
 #define RWF_ATOMIC	((__kernel_rwf_t)0x00000040)
diff --git a/libxfs/xfs_inode_util.c b/libxfs/xfs_inode_util.c
index ccd38f18c3ed..fd8441bf9b83 100644
--- a/libxfs/xfs_inode_util.c
+++ b/libxfs/xfs_inode_util.c
@@ -127,6 +127,8 @@ xfs_ip2xflags(
 
 	if (xfs_inode_has_attr_fork(ip))
 		flags |= FS_XFLAG_HASATTR;
+	if (xfs_has_asciici(ip->i_mount))
+		flags |= FS_XFLAG_CASEFOLD;
 	return flags;
 }
 
-- 
2.55.0