From: André Almeida <andrealmeid@igalia.com>
Date: Thu, 14 Aug 2025 17:22:20 +0000 (-0300)
Subject: ovl: Support mounting case-insensitive enabled layers
X-Git-Tag: v6.18-rc1~122^2~1
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=16754d61dc69cb4550225a967a2639809226de42;p=thirdparty%2Flinux.git

ovl: Support mounting case-insensitive enabled layers

Drop the restriction for casefold dentries lookup to enable support for
case-insensitive layers in overlayfs.

Support case-insensitive layers with the condition that they should be
uniformly enabled across the stack and (i.e. if the root mount dir has
casefold enabled, so should all the dirs bellow for every layer).

Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: André Almeida <andrealmeid@igalia.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---

diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index 76d6248b625e7..e93bcc5727bca 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -239,13 +239,14 @@ static int ovl_lookup_single(struct dentry *base, struct ovl_lookup_data *d,
 	char val;
 
 	/*
-	 * We allow filesystems that are case-folding capable but deny composing
-	 * ovl stack from case-folded directories. If someone has enabled case
-	 * folding on a directory on underlying layer, the warranty of the ovl
-	 * stack is voided.
+	 * We allow filesystems that are case-folding capable as long as the
+	 * layers are consistently enabled in the stack, enabled for every dir
+	 * or disabled in all dirs. If someone has modified case folding on a
+	 * directory on underlying layer, the warranty of the ovl stack is
+	 * voided.
 	 */
-	if (ovl_dentry_casefolded(base)) {
-		warn = "case folded parent";
+	if (ofs->casefold != ovl_dentry_casefolded(base)) {
+		warn = "parent wrong casefold";
 		err = -ESTALE;
 		goto out_warn;
 	}
@@ -259,8 +260,8 @@ static int ovl_lookup_single(struct dentry *base, struct ovl_lookup_data *d,
 		goto out_err;
 	}
 
-	if (ovl_dentry_casefolded(this)) {
-		warn = "case folded child";
+	if (ofs->casefold != ovl_dentry_casefolded(this)) {
+		warn = "child wrong casefold";
 		err = -EREMOTE;
 		goto out_warn;
 	}
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 41033bac96cbb..bec4a39d1b97c 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 layers with casefold, we accept that they have
+	 * their own hash and compare operations
 	 */
 	if (sb_has_encoding(dentry->d_sb))
-		return IS_CASEFOLDED(d_inode(dentry));
+		return false;
 
 	return dentry->d_flags & (DCACHE_OP_HASH | DCACHE_OP_COMPARE);
 }