btrfs-progs: Document logic of btrfs_read_dev_super

[platform/upstream/btrfs-progs.git] / cmds-subvolume.c

diff --git a/cmds-subvolume.c b/cmds-subvolume.c
index 69c5038..dc626a6 100644 (file)
--- a/cmds-subvolume.c
+++ b/cmds-subvolume.c
@@ -439,24 +439,32 @@ keep_fd:
  * - lowercase for enabling specific items in the output
  */
 static const char * const cmd_subvol_list_usage[] = {
-       "btrfs subvolume list [options] [-G [+|-]value] [-C [+|-]value] "
-       "[--sort=gen,ogen,rootid,path] <path>",
-       "List subvolumes (and snapshots)",
+       "btrfs subvolume list [options] <path>",
+       "List subvolumes and snapshots in the filesystem.",
        "",
-       "-p           print parent ID",
+       "Path filtering:",
+       "-o           print only subvolumes below specified path",
        "-a           print all the subvolumes in the filesystem and",
        "             distinguish absolute and relative path with respect",
        "             to the given <path>",
+       "",
+       "Field selection:",
+       "-p           print parent ID",
        "-c           print the ogeneration of the subvolume",
        "-g           print the generation of the subvolume",
-       "-o           print only subvolumes below specified path",
        "-u           print the uuid of subvolumes (and snapshots)",
        "-q           print the parent uuid of the snapshots",
        "-R           print the uuid of the received snapshots",
-       "-t           print the result as a table",
-       "-s           list snapshots only in the filesystem",
+       "",
+       "Type filtering:",
+       "-s           list only snapshots",
        "-r           list readonly subvolumes (including snapshots)",
        "-d           list deleted subvolumes that are not yet cleaned",
+       "",
+       "Other:",
+       "-t           print the result as a table",
+       "",
+       "Sorting:",
        "-G [+|-]value",
        "             filter the subvolumes by generation",
        "             (+value: >= value; -value: <= value; value: = value)",
@@ -850,8 +858,11 @@ out:
 }
 
 static const char * const cmd_subvol_set_default_usage[] = {
+       "btrfs subvolume set-default <subvolume>\n"
        "btrfs subvolume set-default <subvolid> <path>",
-       "Set the default subvolume of a filesystem",
+       "Set the default subvolume of the filesystem mounted as default.",
+       "The subvolume can be specified by its path,",
+       "or the pair of subvolume id and path to the filesystem.",
        NULL
 };
 
@@ -865,17 +876,43 @@ static int cmd_subvol_set_default(int argc, char **argv)
 
        clean_args_no_options(argc, argv, cmd_subvol_set_default_usage);
 
-       if (check_argc_exact(argc - optind, 2))
+       if (check_argc_min(argc - optind, 1) ||
+                       check_argc_max(argc - optind, 2))
                usage(cmd_subvol_set_default_usage);
 
-       subvolid = argv[optind];
-       path = argv[optind + 1];
+       if (argc - optind == 1) {
+               /* path to the subvolume is specified */
+               path = argv[optind];
 
-       objectid = arg_strtou64(subvolid);
+               ret = test_issubvolume(path);
+               if (ret < 0) {
+                       error("stat error: %s", strerror(-ret));
+                       return 1;
+               } else if (!ret) {
+                       error("'%s' is not a subvolume", path);
+                       return 1;
+               }
 
-       fd = btrfs_open_dir(path, &dirstream, 1);
-       if (fd < 0)
-               return 1;
+               fd = btrfs_open_dir(path, &dirstream, 1);
+               if (fd < 0)
+                       return 1;
+
+               ret = lookup_path_rootid(fd, &objectid);
+               if (ret) {
+                       error("unable to get subvol id: %s", strerror(-ret));
+                       close_file_or_dir(fd, dirstream);
+                       return 1;
+               }
+       } else {
+               /* subvol id and path to the filesystem are specified */
+               subvolid = argv[optind];
+               path = argv[optind + 1];
+               objectid = arg_strtou64(subvolid);
+
+               fd = btrfs_open_dir(path, &dirstream, 1);
+               if (fd < 0)
+                       return 1;
+       }
 
        ret = ioctl(fd, BTRFS_IOC_DEFAULT_SUBVOL, &objectid);
        e = errno;