btrfs-progs: subvolume delete: add new option for recursive deletion

Add new option --recursive 'btrfs subvol delete', causing it to pass the
BTRFS_UTIL_DELETE_SUBVOLUME_RECURSIVE flag through to libbtrfsutil.

This can work in two modes, depending on the user:

- regular user - this will skip subvolumes that are not accessible
- root (CAP_SYS_ADMIN) - no limitations

Pull-request: #861
Signed-off-by: Mark Harmstone <maharmstone@meta.com>
Co-authored-by: Omar Sandoval <osandov@osandov.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
[ Add details to man page, fix indent in the doc. ]
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Documentation/btrfs-subvolume.rst

@@ -112,6 +112,15 @@ delete [options] [<subvolume> [<subvolume>...]], delete -i|--subvolid <subvolid>
         -i|--subvolid <subvolid>
                 subvolume id to be removed instead of the <path> that should point to the
                 filesystem with the subvolume
+
+        -R|--recursive
+                delete subvolumes beneath each subvolume recursively
+
+                This requires either `CAP_SYS_ADMIN` or the filesystem must be
+                mounted with `user_subvol_rm_allowed` mount option.
+                In the unprivileged case, subvolumes which cannot be accessed
+                are skipped.  The deletion is not atomic.
+
         -v|--verbose
                 (deprecated) alias for global *-v* option
 

cmds/subvolume.c

@@ -347,6 +347,8 @@ static const char * const cmd_subvolume_delete_usage[] = {
 	OPTLINE("-c|--commit-after", "wait for transaction commit at the end of the operation"),
 	OPTLINE("-C|--commit-each", "wait for transaction commit after deleting each subvolume"),
 	OPTLINE("-i|--subvolid", "subvolume id of the to be removed subvolume"),
+	OPTLINE("-R|--recursive", "delete accessible subvolumes beneath each subvolume recursively, "
+		"this is not atomic, may need root to delete subvolumes not accessible by the user"),
 	OPTLINE("-v|--verbose", "deprecated, alias for global -v option"),
 	HELPINFO_INSERT_GLOBALS,
 	HELPINFO_INSERT_VERBOSE,
@@ -367,6 +369,7 @@ static int cmd_subvolume_delete(const struct cmd_struct *cmd, int argc, char **a
 	char	*path = NULL;
 	int commit_mode = 0;
 	bool subvol_path_not_found = false;
+	int flags = 0;
 	u8 fsid[BTRFS_FSID_SIZE];
 	u64 subvolid = 0;
 	char uuidbuf[BTRFS_UUID_UNPARSED_SIZE];
@@ -383,11 +386,12 @@ static int cmd_subvolume_delete(const struct cmd_struct *cmd, int argc, char **a
 			{"commit-after", no_argument, NULL, 'c'},
 			{"commit-each", no_argument, NULL, 'C'},
 			{"subvolid", required_argument, NULL, 'i'},
+			{"recursive", no_argument, NULL, 'R'},
 			{"verbose", no_argument, NULL, 'v'},
 			{NULL, 0, NULL, 0}
 		};
 
-		c = getopt_long(argc, argv, "cCi:v", long_options, NULL);
+		c = getopt_long(argc, argv, "cCi:Rv", long_options, NULL);
 		if (c < 0)
 			break;
 
@@ -401,6 +405,9 @@ static int cmd_subvolume_delete(const struct cmd_struct *cmd, int argc, char **a
 		case 'i':
 			subvolid = arg_strtou64(optarg);
 			break;
+		case 'R':
+			flags |= BTRFS_UTIL_DELETE_SUBVOLUME_RECURSIVE;
+			break;
 		case 'v':
 			bconf_be_verbose();
 			break;
@@ -416,6 +423,11 @@ static int cmd_subvolume_delete(const struct cmd_struct *cmd, int argc, char **a
 	if (subvolid > 0 && check_argc_exact(argc - optind, 1))
 		return 1;
 
+	if (subvolid > 0 && flags & BTRFS_UTIL_DELETE_SUBVOLUME_RECURSIVE) {
+		error("option --recursive is not supported with --subvolid");
+		return 1;
+	}
+
 	pr_verbose(LOG_INFO, "Transaction commit: %s\n",
 		   !commit_mode ? "none (default)" :
 		   commit_mode == COMMIT_AFTER ? "at the end" : "after each");
@@ -528,7 +540,7 @@ static int cmd_subvolume_delete(const struct cmd_struct *cmd, int argc, char **a
 
 	/* Start deleting. */
 	if (subvolid == 0)
-		err = btrfs_util_delete_subvolume_fd(fd, vname, 0);
+		err = btrfs_util_delete_subvolume_fd(fd, vname, flags);
 	else
 		err = btrfs_util_delete_subvolume_by_id_fd(fd, subvolid);
 	if (err) {