Info drop internal xattrs

libcomposefs/lcfs-internal.h

@@ -48,27 +48,49 @@ typedef int errint_t;
 #define OVERLAY_XATTR_USER_PREFIX "user."
 #define OVERLAY_XATTR_TRUSTED_PREFIX "trusted."
 #define OVERLAY_XATTR_PARTIAL_PREFIX "overlay."
+// trusted.overlay.
 #define OVERLAY_XATTR_PREFIX                                                   \
 	OVERLAY_XATTR_TRUSTED_PREFIX OVERLAY_XATTR_PARTIAL_PREFIX
+// user.overlay.
 #define OVERLAY_XATTR_USERXATTR_PREFIX                                         \
 	OVERLAY_XATTR_USER_PREFIX OVERLAY_XATTR_PARTIAL_PREFIX
+// trusted.overlay.overlay.
 #define OVERLAY_XATTR_ESCAPE_PREFIX OVERLAY_XATTR_PREFIX "overlay."
+// trusted.overlay.metacopy
 #define OVERLAY_XATTR_METACOPY OVERLAY_XATTR_PREFIX "metacopy"
+// trusted.overlay.redirect
 #define OVERLAY_XATTR_REDIRECT OVERLAY_XATTR_PREFIX "redirect"
+// trusted.overlay.whiteout
 #define OVERLAY_XATTR_WHITEOUT OVERLAY_XATTR_PREFIX "whiteout"
+// trusted.overlay.whiteouts
 #define OVERLAY_XATTR_WHITEOUTS OVERLAY_XATTR_PREFIX "whiteouts"
+// trusted.overlay.opaque
 #define OVERLAY_XATTR_OPAQUE OVERLAY_XATTR_PREFIX "opaque"
 
+// user.overlay.overlay.
+#define OVERLAY_XATTR_USERXATTR_ESCAPE_PREFIX                                  \
+	OVERLAY_XATTR_USERXATTR_PREFIX "overlay."
+
+// trusted.overlay.overlay.whiteout
 #define OVERLAY_XATTR_ESCAPED_WHITEOUT OVERLAY_XATTR_ESCAPE_PREFIX "whiteout"
+// trusted.overlay.overlay.whiteouts
 #define OVERLAY_XATTR_ESCAPED_WHITEOUTS OVERLAY_XATTR_ESCAPE_PREFIX "whiteouts"
+// trusted.overlay.overlay.opaque
 #define OVERLAY_XATTR_ESCAPED_OPAQUE OVERLAY_XATTR_ESCAPE_PREFIX "opaque"
 
+// user.overlay.whiteout
 #define OVERLAY_XATTR_USERXATTR_WHITEOUT                                       \
 	OVERLAY_XATTR_USERXATTR_PREFIX "whiteout"
+// user.overlay.whiteouts
 #define OVERLAY_XATTR_USERXATTR_WHITEOUTS                                      \
 	OVERLAY_XATTR_USERXATTR_PREFIX "whiteouts"
+// user.overlay.opaque
 #define OVERLAY_XATTR_USERXATTR_OPAQUE OVERLAY_XATTR_USERXATTR_PREFIX "opaque"
 
+// user.overlay.overlay.opaque
+#define OVERLAY_XATTR_USERXATTR_ESCAPED_OPAQUE                                 \
+	OVERLAY_XATTR_USERXATTR_ESCAPE_PREFIX "opaque"
+
 #define ALIGN_TO(_offset, _align_size)                                         \
 	(((_offset) + _align_size - 1) & ~(_align_size - 1))
 

libcomposefs/lcfs-writer-erofs.c

@@ -1150,14 +1150,17 @@ static int add_overlayfs_xattrs(struct lcfs_ctx_s *ctx, struct lcfs_node_s *node
 		if (ret < 0)
 			return ret;
 
-		/* Mark dir containing whiteouts with new format as of version 1 */
+		/* Mark dir containing whiteouts with new format as of version 1;
+		 * note the code in composefs-info.c which explicitly skips these.
+		 */
 		if (ctx->options->version >= 1) {
 			ret = lcfs_node_set_xattr(
 				parent, OVERLAY_XATTR_ESCAPED_OPAQUE, "x", 1);
 			if (ret < 0)
 				return ret;
 			ret = lcfs_node_set_xattr(
-				parent, OVERLAY_XATTR_USERXATTR_OPAQUE, "x", 1);
+				parent, OVERLAY_XATTR_USERXATTR_ESCAPED_OPAQUE,
+				"x", 1);
 			if (ret < 0)
 				return ret;
 		}
@@ -1522,6 +1525,7 @@ static int erofs_readdir_block(struct lcfs_image_data *data,
 	return 0;
 }
 
+// Convert an EROFS entry back into a composefs node.
 static int lcfs_build_node_erofs_xattr(struct lcfs_node_s *node, uint8_t name_index,
 				       const char *entry_name, uint8_t name_len,
 				       const char *value, uint16_t value_size)
@@ -1579,6 +1583,17 @@ static int lcfs_build_node_erofs_xattr(struct lcfs_node_s *node, uint8_t name_in
 			return 0;
 		}
 	}
+	if (str_has_prefix(name, OVERLAY_XATTR_USERXATTR_PREFIX)) {
+		if (str_has_prefix(name, OVERLAY_XATTR_USERXATTR_ESCAPE_PREFIX)) {
+			/* Unescape */
+			memmove(name + strlen(OVERLAY_XATTR_USER_PREFIX),
+				name + strlen(OVERLAY_XATTR_USERXATTR_PREFIX),
+				strlen(name) - strlen(OVERLAY_XATTR_USER_PREFIX) + 1);
+		} else {
+			/* skip */
+			return 0;
+		}
+	}
 
 	if (lcfs_node_set_xattr(node, name, value, value_size) < 0)
 		return -1;

tests/test-units.sh

@@ -19,6 +19,22 @@ function countobjects () {
     find $dir/objects -type f | wc -l
 }
 
+# Test a full cycle of roundtrips through mkcomposefs --from-file, composefs-info dump, etc.
+function test_dump_roundtrip () {
+    testsrcdir=$(cd $(dirname $0) && pwd)
+    pushd $1
+    local src=$testsrcdir/assets/special.dump
+    set -x
+    $BINDIR/mkcomposefs --from-file "${src}" out.cfs
+    $BINDIR/composefs-info dump out.cfs > dump.txt
+    diff -u "${src}" dump.txt || exit 1
+    $BINDIR/mkcomposefs --from-file dump.txt out2.cfs
+    diff -u out.cfs out2.cfs || exit 1
+    echo "ok dump roundtrip"
+    popd
+}
+
+
 # Ensure small files are inlined
 function  test_inline () {
     local dir=$1
@@ -86,7 +102,7 @@ function test_composefs_info_measure_files () {
     cd -
 }
 
-TESTS="test_inline test_objects test_mount_digest test_composefs_info_measure_files"
+TESTS="test_dump_roundtrip test_inline test_objects test_mount_digest test_composefs_info_measure_files"
 res=0
 for i in $TESTS; do
     testdir=$(mktemp -d $workdir/$i.XXXXXX)

tools/composefs-info.c

@@ -236,6 +236,22 @@ static void dump_node(struct lcfs_node_s *node, char *path)
 		size_t value_len;
 		const char *value = lcfs_node_get_xattr(target, name, &value_len);
 
+		// Skip the special xattrs injected by lcfs-writer-erofs.c to
+		// denote a directory containing whiteouts.
+		bool is_opaque_flag =
+			(strcmp(name, OVERLAY_XATTR_OPAQUE) == 0) ||
+			(strcmp(name, OVERLAY_XATTR_USERXATTR_OPAQUE) == 0);
+		bool is_special_x = value_len == 1 && *value == 'x';
+		if (is_opaque_flag && is_special_x) {
+			continue;
+		}
+
+		// Undo the effect of the escaping in add_overlayfs_xattrs
+		if (str_has_prefix(name, OVERLAY_XATTR_ESCAPE_PREFIX)) {
+			name += strlen(OVERLAY_XATTR_ESCAPE_PREFIX);
+		} else if (str_has_prefix(name, OVERLAY_XATTR_USERXATTR_ESCAPE_PREFIX)) {
+			name += strlen(OVERLAY_XATTR_USERXATTR_ESCAPE_PREFIX);
+		}
 		printf(" ");
 		print_escaped(name, -1, ESCAPE_EQUAL);
 		printf("=");