btrfs-progs: tests: add hardlink related tests for mkfs --subvol

This introduces two new cases:

- 3 hardlinks without any subvolume
  This should results 3 hard links inside the btrfs.

- 3 hardlinks, but a subvolume will split 2 of them
  Then the 2 inside the same subvolume should still report 2 nlinks,
  but the lone one inside the new subvolume can only report 1 nlink.

Signed-off-by: Qu Wenruo <wqu@suse.com>

mkfs/rootdir.c

@@ -725,7 +725,7 @@ static int ftw_add_inode(const char *full_path, const struct stat *st,
 	parent = rootdir_path_last(&current_path);
 	root = parent->root;
 
-	/* For non-directory inode, check if there is already any hard link. */
+	/* Check if there is already a hard link record for this. */
 	if (have_hard_links) {
 		struct hardlink_entry *found;
 
@@ -771,6 +771,7 @@ static int ftw_add_inode(const char *full_path, const struct stat *st,
 		error("failed to insert inode item %llu for '%s': %m", ino, full_path);
 		return ret;
 	}
+
 	ret = btrfs_add_link(g_trans, root, ino, parent->ino,
 			     full_path + ftwbuf->base,
 			     strlen(full_path) - ftwbuf->base,
@@ -782,10 +783,7 @@ static int ftw_add_inode(const char *full_path, const struct stat *st,
 		return ret;
 	}
 
-	/*
-	 * Found a possible hard link, add it into the hard link rb tree for
-	 * future detection.
-	 */
+	/* Record this new hard link. */
 	if (have_hard_links) {
 		ret = add_hard_link(root, ino, st);
 		if (ret < 0) {

tests/mkfs-tests/036-rootdir-subvol/test.sh

@@ -11,6 +11,8 @@ prepare_test_dev
 
 tmp=$(_mktemp_dir mkfs-rootdir)
 
+basic()
+{
 	run_check touch "$tmp/foo"
 	run_check mkdir "$tmp/dir"
 	run_check mkdir "$tmp/dir/subvol"
@@ -29,5 +31,55 @@ result=$(cat "$tmp/output")
 	if [ "$result" != "dir/subvol" ]; then
 		_fail "dir/subvol not in subvolume list"
 	fi
+	rm -rf -- "$tmp/foo" "$tmp/dir"
+}
 
+basic_hardlinks()
+{
+	run_check touch "$tmp/hl1"
+	run_check ln "$tmp/hl1" "$tmp/hl2"
+	run_check mkdir "$tmp/dir"
+	run_check ln "$tmp/hl1" "$tmp/dir/hl3"
+
+	run_check_mkfs_test_dev --rootdir "$tmp"
+	run_check $SUDO_HELPER "$TOP/btrfs" check "$TEST_DEV"
+
+	run_check_mount_test_dev
+	nr_hardlink=$(run_check_stdout $SUDO_HELPER stat -c "%h" "$TEST_MNT/hl1")
+
+	if [ "$nr_hardlink" -ne 3 ]; then
+		_fail "hard link number incorrect, has ${nr_hardlink} expect 3"
+	fi
+	run_check_umount_test_dev
+	rm -rf -- "$tmp/hl1" "$tmp/hl2" "$tmp/dir"
+}
+
+split_by_subvolume_hardlinks()
+{
+	run_check touch "$tmp/hl1"
+	run_check ln "$tmp/hl1" "$tmp/hl2"
+	run_check mkdir "$tmp/subv"
+	run_check ln "$tmp/hl1" "$tmp/subv/hl3"
+
+	run_check_mkfs_test_dev --rootdir "$tmp" --subvol subv
+	run_check $SUDO_HELPER "$TOP/btrfs" check "$TEST_DEV"
+
+	run_check_mount_test_dev
+	nr_hardlink=$(run_check_stdout $SUDO_HELPER stat -c "%h" "$TEST_MNT/hl1")
+
+	if [ "$nr_hardlink" -ne 2 ]; then
+		_fail "hard link number incorrect for hl1, has ${nr_hardlink} expect 2"
+	fi
+
+	nr_hardlink=$(run_check_stdout $SUDO_HELPER stat -c "%h" "$TEST_MNT/subv/hl3")
+	if [ "$nr_hardlink" -ne 1 ]; then
+		_fail "hard link number incorrect for subv/hl3, has ${nr_hardlink} expect 1"
+	fi
+	run_check_umount_test_dev
+	rm -rf -- "$tmp/hl1" "$tmp/hl2" "$tmp/dir"
+}
+
+basic
+basic_hardlinks
+split_by_subvolume_hardlinks
 rm -rf -- "$tmp"