btrfs-progs: subvolume: add new command for listing

Work in progress, experimental build. Listing command that utilizes
unprivileged ioctls to list subvolumes accessible and visible to the
user. If run as root it's using the search tree ioctl and has complete
information.

Reduced tabular output by default.

Issue: #515
Signed-off-by: David Sterba <dsterba@suse.com>

cmds/commands.h

@@ -131,6 +131,7 @@ extern const char * const generic_cmd_help_usage[];
 
 DECLARE_COMMAND(subvolume);
 DECLARE_COMMAND(subvolume_list);
+DECLARE_COMMAND(subvolume_ls);
 DECLARE_COMMAND(filesystem);
 DECLARE_COMMAND(filesystem_du);
 DECLARE_COMMAND(filesystem_usage);

cmds/subvolume-list.c

@@ -27,12 +27,14 @@
 #include "kernel-lib/rbtree.h"
 #include "kernel-lib/rbtree_types.h"
 #include "kernel-shared/ctree.h"
+#include "libbtrfsutil/btrfsutil.h"
 #include "common/defs.h"
 #include "common/rbtree-utils.h"
 #include "common/help.h"
 #include "common/messages.h"
 #include "common/open-utils.h"
 #include "common/string-utils.h"
+#include "common/string-table.h"
 #include "common/utils.h"
 #include "cmds/commands.h"
 #include "ioctl.h"
@@ -1642,3 +1644,118 @@ out:
 	return !!ret;
 }
 DEFINE_SIMPLE_COMMAND(subvolume_list, "list");
+
+static const char * const cmd_subvolume_ls_usage[] = {
+	"btrfs subvolume ls [options] <path>",
+	"New interface for subvolume listing.",
+	"New interface for subvolume listing.",
+	NULL
+};
+
+static int cmd_subvolume_ls(const struct cmd_struct *cmd, int argc, char **argv)
+{
+	int fd = -1;
+	int ret = -1;
+	char *subvol;
+	DIR *dirstream = NULL;
+	struct btrfs_util_subvolume_iterator *iter;
+	enum btrfs_util_error err;
+	struct string_table *tab = NULL;
+	unsigned int row;
+	int i;
+	enum {
+		C_SUBVOLID, C_GENERATION, C_FLAGS, C_PATH,
+		C_COLUMN_COUNT
+	};
+
+	optind = 0;
+	while (1) {
+		int c;
+		static const struct option long_options[] = {
+			{NULL, 0, NULL, 0}
+		};
+
+		c = getopt_long(argc, argv, "", long_options, NULL);
+		if (c < 0)
+			break;
+
+		switch (c) {
+		default:
+			usage_unknown_option(cmd, argv);
+		}
+	}
+
+	if (check_argc_exact(argc - optind, 1))
+		goto out;
+
+	subvol = argv[optind];
+	fd = btrfs_open_dir(subvol, &dirstream, 1);
+	if (fd < 0) {
+		ret = -1;
+		error("can't access '%s'", subvol);
+		goto out;
+	}
+
+	pr_verbose(LOG_DEBUG, "Create iterator\n");
+	err = btrfs_util_create_subvolume_iterator_fd(fd, 0, 0, &iter);
+	if (err) {
+		error_btrfs_util(err);
+		goto out;
+	}
+
+	tab = table_create(C_COLUMN_COUNT, 20);
+	if (!tab) {
+		error("not enough memory");
+		goto out;
+	}
+	tab->hrows = 2;
+	row = tab->hrows;
+	table_printf(tab, C_SUBVOLID, 0, "<Subvolid");
+	table_printf(tab, C_GENERATION, 0, "<Generation");
+	table_printf(tab, C_FLAGS, 0, "<Flags");
+	table_printf(tab, C_PATH, 0, "<Path");
+	for (i = 0; i < tab->ncols; i++)
+		table_printf(tab, i, 1, "*-");
+
+	while (1) {
+		struct btrfs_util_subvolume_info subvol;
+		char *path;
+		char str_flags[16] = { 0 };
+
+		err = btrfs_util_subvolume_iterator_next_info(iter, &path, &subvol);
+		if (err == BTRFS_UTIL_ERROR_STOP_ITERATION) {
+			table_dump(tab);
+			goto out;
+		} else if (err) {
+			error_btrfs_util(err);
+			btrfs_util_destroy_subvolume_iterator(iter);
+			goto out;
+		}
+		if (!uuid_is_null(subvol.parent_uuid))
+			str_flags[0] = 's';
+		else
+			str_flags[0] = 'u';
+		if (subvol.flags & BTRFS_ROOT_SUBVOL_RDONLY)
+			str_flags[1] = 'r';
+		else
+			str_flags[1] = 'w';
+		if (!uuid_is_null(subvol.received_uuid))
+			str_flags[2] = 'R';
+		table_printf(tab, C_SUBVOLID, row, ">%llu", subvol.id);
+		table_printf(tab, C_GENERATION, row, ">%llu", subvol.generation);
+		table_printf(tab, C_FLAGS, row, ">%s", str_flags);
+		table_printf(tab, C_PATH, row, "<%s", path);
+		free(path);
+		row++;
+		if (row >= tab->nrows)
+			break;
+	}
+	btrfs_util_destroy_subvolume_iterator(iter);
+	table_dump(tab);
+
+out:
+	table_free(tab);
+	close_file_or_dir(fd, dirstream);
+	return !!ret;
+}
+DEFINE_SIMPLE_COMMAND(subvolume_ls, "ls");

cmds/subvolume.c

@@ -1615,6 +1615,9 @@ static const struct cmd_group subvolume_cmd_group = {
 		&cmd_struct_subvolume_create,
 		&cmd_struct_subvolume_delete,
 		&cmd_struct_subvolume_list,
+#if EXPERIMENTAL
+		&cmd_struct_subvolume_ls,
+#endif
 		&cmd_struct_subvolume_snapshot,
 		&cmd_struct_subvolume_get_default,
 		&cmd_struct_subvolume_set_default,