Allow creating empty filesystem images

Support creating empty filesystem images by making the source directory
argument optional.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

diff --git a/make_ext4fs.c b/make_ext4fs.c
index dd4d0d3f301ab45d2135d28e5af5ce47ac3919ad..bf5f49fb115f6c2ba37a2aef5f311780aff7f430 100644 (file)
--- a/make_ext4fs.c
+++ b/make_ext4fs.c
@@ -45,6 +45,27 @@ static int filter_dot(const struct dirent *d)
        return (strcmp(d->d_name, "..") && strcmp(d->d_name, "."));
 }
 
+static u32 build_default_directory_structure(time_t fixed_time)
+{
+       u32 inode;
+       u32 root_inode;
+       struct dentry dentries = {
+               .filename = "lost+found",
+               .file_type = EXT4_FT_DIR,
+               .mode = S_IRWXU,
+               .uid = 0,
+               .gid = 0,
+               .mtime = (fixed_time != -1) ? fixed_time : 0,
+       };
+       root_inode = make_directory(0, 1, &dentries, 1);
+       inode = make_directory(root_inode, 0, NULL, 0);
+       *dentries.inode = inode;
+       inode_set_permissions(inode, dentries.mode,
+               dentries.uid, dentries.gid, dentries.mtime);
+
+       return root_inode;
+}
+
 /* Read a local directory and create the same tree in the generated filesystem.
    Calls itself recursively with each directory in the given directory.
    full_path is an absolute or relative path, with a trailing slash, to the
@@ -367,12 +388,8 @@ int make_ext4fs_internal(int fd, const char *_directory,
        if (setjmp(setjmp_env))
                return EXIT_FAILURE; /* Handle a call to longjmp() */
 
-       if (_directory == NULL) {
-               fprintf(stderr, "Need a source directory\n");
-               return EXIT_FAILURE;
-       }
-
-       directory = canonicalize_rel_slashes(_directory);
+       if (_directory)
+               directory = canonicalize_rel_slashes(_directory);
 
        if (info.len <= 0)
                info.len = get_file_size(fd);
@@ -457,11 +474,15 @@ int make_ext4fs_internal(int fd, const char *_directory,
        if (info.feat_compat & EXT4_FEATURE_COMPAT_RESIZE_INODE)
                ext4_create_resize_inode();
 
-       root_inode_num = build_directory_structure(directory, "", 0,
-               fs_config_func, verbose, fixed_time);
+       if (directory)
+               root_inode_num = build_directory_structure(directory, "", 0,
+                       fs_config_func, verbose, fixed_time);
+       else
+               root_inode_num = build_default_directory_structure(fixed_time);
 
        root_mode = S_IRWXU | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH;
-       inode_set_permissions(root_inode_num, root_mode, 0, 0, 0);
+       inode_set_permissions(root_inode_num, root_mode, 0, 0,
+               (fixed_time != 1) ? fixed_time : 0);
 
        ext4_update_free();