ovl: Add OVL_XATTR_TRUSTED/USER_PREFIX_LEN macros

These match the ones for e.g. XATTR_TRUSTED_PREFIX_LEN.
Signed-off-by: Alexander Larsson <alexl@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>

fs/overlayfs/overlayfs.h

@@ -28,7 +28,9 @@ enum ovl_path_type {
 
 #define OVL_XATTR_NAMESPACE "overlay."
 #define OVL_XATTR_TRUSTED_PREFIX XATTR_TRUSTED_PREFIX OVL_XATTR_NAMESPACE
+#define OVL_XATTR_TRUSTED_PREFIX_LEN (sizeof(OVL_XATTR_TRUSTED_PREFIX) - 1)
 #define OVL_XATTR_USER_PREFIX XATTR_USER_PREFIX OVL_XATTR_NAMESPACE
+#define OVL_XATTR_USER_PREFIX_LEN (sizeof(OVL_XATTR_USER_PREFIX) - 1)
 
 enum ovl_xattr {
 	OVL_XATTR_OPAQUE,

fs/overlayfs/xattrs.c

@@ -10,10 +10,10 @@ bool ovl_is_private_xattr(struct super_block *sb, const char *name)
 
 	if (ofs->config.userxattr)
 		return strncmp(name, OVL_XATTR_USER_PREFIX,
-			       sizeof(OVL_XATTR_USER_PREFIX) - 1) == 0;
+			       OVL_XATTR_USER_PREFIX_LEN) == 0;
 	else
 		return strncmp(name, OVL_XATTR_TRUSTED_PREFIX,
-			       sizeof(OVL_XATTR_TRUSTED_PREFIX) - 1) == 0;
+			       OVL_XATTR_TRUSTED_PREFIX_LEN) == 0;
 }
 
 static int ovl_xattr_set(struct dentry *dentry, struct inode *inode, const char *name,