linux-kernel - [PATCH RFC v2 8/8] ovl: Drop restrictions for casefolded dentries

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Message-Id: <20250805-tonyk-overlayfs-v2-8-0e54281da318@igalia.com>
Date: Tue, 05 Aug 2025 00:09:12 -0300
From: André Almeida <andrealmeid@...lia.com>
To: Miklos Szeredi <miklos@...redi.hu>, Amir Goldstein <amir73il@...il.com>, 
 Theodore Tso <tytso@....edu>, Gabriel Krisman Bertazi <krisman@...nel.org>
Cc: linux-unionfs@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-fsdevel@...r.kernel.org, Alexander Viro <viro@...iv.linux.org.uk>, 
 Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>, 
 kernel-dev@...lia.com, 
 André Almeida <andrealmeid@...lia.com>
Subject: [PATCH RFC v2 8/8] ovl: Drop restrictions for casefolded dentries

Drop the restriction for casefold dentries to enable support for
casefold filesystems in overlayfs.

Signed-off-by: André Almeida <andrealmeid@...lia.com>
---
 fs/overlayfs/params.c | 7 -------
 fs/overlayfs/util.c   | 8 ++++----
 2 files changed, 4 insertions(+), 11 deletions(-)

diff --git a/fs/overlayfs/params.c b/fs/overlayfs/params.c
index f4e7fff909ac49e2f8c58a76273426c1158a7472..dd3a893d37603842f7d19d90accb981f0d12e971 100644
--- a/fs/overlayfs/params.c
+++ b/fs/overlayfs/params.c
@@ -281,13 +281,6 @@ static int ovl_mount_dir_check(struct fs_context *fc, const struct path *path,
 	if (!d_is_dir(path->dentry))
 		return invalfc(fc, "%s is not a directory", name);
 
-	/*
-	 * Allow filesystems that are case-folding capable but deny composing
-	 * ovl stack from case-folded directories.
-	 */
-	if (ovl_dentry_casefolded(path->dentry))
-		return invalfc(fc, "case-insensitive directory on %s not supported", name);
-
 	if (ovl_dentry_weird(path->dentry))
 		return invalfc(fc, "filesystem on %s not supported", name);
 
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index a33115e7384c129c543746326642813add63f060..7a6ee058568283453350153c1720c35e11ad4d1b 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -210,11 +210,11 @@ bool ovl_dentry_weird(struct dentry *dentry)
 		return true;
 
 	/*
-	 * Allow filesystems that are case-folding capable but deny composing
-	 * ovl stack from case-folded directories.
+	 * Exceptionally for casefold dentries, we accept that they have their
+	 * own hash and compare operations
 	 */
-	if (sb_has_encoding(dentry->d_sb))
-		return IS_CASEFOLDED(d_inode(dentry));
+	if (ovl_dentry_casefolded(dentry))
+		return false;
 
 	return dentry->d_flags & (DCACHE_OP_HASH | DCACHE_OP_COMPARE);
 }

-- 
2.50.1