ext4l: Add ls command support

Implement directory listing (ls) for the ext4l filesystem driver. This
includes path resolution with symlink following (limited to 8 levels to
prevent loops).

Add ext4l_ls() which uses ext4_lookup() for path resolution and
ext4_readdir() for directory enumeration. The dir_context actor callback
formats and prints each directory entry.

Export ext4_lookup() from namei.c and add declarations to ext4.h.

Add test_ls to the Python test suite, which creates a test file using
debugfs and verifies it appears in the directory listing with the
correct size.

Co-developed-by: Claude Opus 4.5 <noreply@anthropic.com>

Cover-letter:
ext4l: Add support for listing directoties (Part H)
This series adds directory-listing support to the ext4l filesystem
driver. It exports a few required functions from the Linux ext4 code,
fixes the dir_emit() stub to properly call the actor callback, and
implements ext4l_ls() with path resolution and symlink following.
END

Signed-off-by: Simon Glass <simon.glass@canonical.com>

test/fs/ext4l.c

@@ -79,3 +79,32 @@ static int fs_test_ext4l_msgs_norun(struct unit_test_state *uts)
 }
 FS_TEST_ARGS(fs_test_ext4l_msgs_norun, UTF_SCAN_FDT | UTF_CONSOLE | UTF_MANUAL,
 	     { "fs_image", UT_ARG_STR });
+
+/**
+ * fs_test_ext4l_ls_norun() - Test ext4l ls command
+ *
+ * This test verifies that the ext4l driver can list directory contents.
+ *
+ * Arguments:
+ *   fs_image: Path to the ext4 filesystem image
+ */
+static int fs_test_ext4l_ls_norun(struct unit_test_state *uts)
+{
+	const char *fs_image = ut_str(EXT4L_ARG_IMAGE);
+
+	ut_assertnonnull(fs_image);
+	ut_assertok(run_commandf("host bind 0 %s", fs_image));
+	console_record_reset_enable();
+	ut_assertok(run_commandf("ls host 0"));
+	/*
+	 * The Python test adds testfile.txt (12 bytes) to the image.
+	 * Directory entries appear in hash order which varies between runs.
+	 * Verify the file entry appears with correct size (12 bytes).
+	 */
+	ut_assert_skip_to_line("       12   testfile.txt");
+	ut_assert_console_end();
+
+	return 0;
+}
+FS_TEST_ARGS(fs_test_ext4l_ls_norun, UTF_SCAN_FDT | UTF_CONSOLE | UTF_MANUAL,
+	     { "fs_image", UT_ARG_STR });

test/py/tests/test_fs/test_ext4l.py

@@ -10,6 +10,7 @@ Test ext4l filesystem probing via C unit test.
 
 import os
 from subprocess import CalledProcessError, check_call
+from tempfile import NamedTemporaryFile
 
 import pytest
 
@@ -35,6 +36,17 @@ class TestExt4l:
             check_call(f'dd if=/dev/zero of={image_path} bs=1M count=64 2>/dev/null',
                        shell=True)
             check_call(f'mkfs.ext4 -q {image_path}', shell=True)
+
+            # Add a test file using debugfs (no mount required)
+            with NamedTemporaryFile(mode='w', delete=False) as tmp:
+                tmp.write('hello world\n')
+                tmp_path = tmp.name
+            try:
+                check_call(f'debugfs -w {image_path} '
+                           f'-R "write {tmp_path} testfile.txt" 2>/dev/null',
+                           shell=True)
+            finally:
+                os.unlink(tmp_path)
         except CalledProcessError:
             pytest.skip('Failed to create ext4 image')
 
@@ -57,3 +69,10 @@ class TestExt4l:
             output = ubman.run_command(
                 f'ut -f fs fs_test_ext4l_msgs_norun fs_image={ext4_image}')
             assert 'failures: 0' in output
+
+    def test_ls(self, ubman, ext4_image):
+        """Test that ext4l can list directory contents."""
+        with ubman.log.section('Test ext4l ls'):
+            output = ubman.run_command(
+                f'ut -f fs fs_test_ext4l_ls_norun fs_image={ext4_image}')
+            assert 'failures: 0' in output