linux-kernel - [PATCH v2 4/6] ext4: Report case sensitivity in fileattr

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Message-ID: <20251211152116.480799-5-cel@kernel.org>
Date: Thu, 11 Dec 2025 10:21:14 -0500
From: Chuck Lever <cel@...nel.org>
To: Al Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>
Cc: <linux-fsdevel@...r.kernel.org>,
	linux-ext4@...r.kernel.org,
	<linux-nfs@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	hirofumi@...l.parknet.co.jp,
	almaz.alexandrovich@...agon-software.com,
	tytso@....edu,
	adilger.kernel@...ger.ca,
	Volker.Lendecke@...net.de,
	Chuck Lever <chuck.lever@...cle.com>
Subject: [PATCH v2 4/6] ext4: Report case sensitivity in fileattr_get

From: Chuck Lever <chuck.lever@...cle.com>

Report ext4's case sensitivity behavior via file_kattr.case_info.
ext4 always preserves case at rest.

Case sensitivity is a per-directory setting in ext4. If the queried
inode is a casefolded directory, report Unicode case-insensitive
matching; otherwise report case-sensitive (standard POSIX behavior).

This enables file_getattr to report the case sensitivity behavior of
individual directories within an ext4 filesystem.

Signed-off-by: Chuck Lever <chuck.lever@...cle.com>
---
 fs/ext4/ioctl.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index a93a7baae990..d760657bb9e2 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -996,6 +996,18 @@ int ext4_fileattr_get(struct dentry *dentry, struct file_kattr *fa)
 	if (ext4_has_feature_project(inode->i_sb))
 		fa->fsx_projid = from_kprojid(&init_user_ns, ei->i_projid);
 
+	/*
+	 * ext4 always preserves case. If this inode is a casefolded
+	 * directory, report Unicode case-insensitive; otherwise
+	 * report case-sensitive (standard POSIX behavior).
+	 */
+	if (IS_CASEFOLDED(inode))
+		fa->case_info = FILEATTR_CASEFOLD_UNICODE |
+				FILEATTR_CASE_PRESERVING;
+	else
+		fa->case_info = FILEATTR_CASEFOLD_NONE |
+				FILEATTR_CASE_PRESERVING;
+
 	return 0;
 }
 
-- 
2.52.0