Theodore Tso wrote:
On Fri, Jul 27, 2007 at 08:29:31AM +0530, Aneesh Kumar K.V wrote:
What are the issues you see with PATCH 1 and PATCH 2 which implement Undo I/O Manager and undoe2fs other than it is not hooked into any of
the existing tools. I will try to add it to mke2fs as you suggested. But
should that prevent it from going in ?

The main issue is that it's not used by an in-tree caller.  If you can
add it to mke2fs, that would be great;


diff --git a/misc/mke2fs.c b/misc/mke2fs.c
index 0c6d4f3..fab8830 100644
--- a/misc/mke2fs.c
+++ b/misc/mke2fs.c
@@ -1521,6 +1521,92 @@ static void PRS(int argc, char *argv[])
                                                fs_param.s_blocks_count);
}

+static int fileystem_exist(const char *name)
+{
+       int retval;
+       io_channel channel;
+       __u16   s_magic;
+       struct ext2_super_block super;
+       io_manager manager = unix_io_manager;
+
+       retval = manager->open(name, IO_FLAG_EXCLUSIVE,  &channel);
+       if (retval) {
+               retval = 0;
+               goto open_err_out;
+       }
+
+       io_channel_set_blksize(channel, SUPERBLOCK_OFFSET);
+       retval = io_channel_read_blk(channel, 1, -SUPERBLOCK_SIZE, &super);
+       if (retval) {
+               retval = 0;
+               goto err_out;
+       }
+
+#if defined(WORDS_BIGENDIAN)
+       s_magic = ext2fs_swab16(super.s_magic);
+#else
+       s_magic = super.s_magic;
+#endif
+
+       if (s_magic == EXT2_SUPER_MAGIC)
+               retval = 1;
+
+err_out:
+       io_channel_close(channel);
+
+open_err_out:
+
+       /*
+        * We don't handle error cases instead we
+        * declare that the file system doesn't exist
+        * and let the rest of mke2fs take care of
+        * error
+        */
+       return retval;
+}
+
+static int mke2fs_setup_tdb(const char *name)
+{
+       char *tdb_dir, tdb_file[PATH_MAX];
+#if 0 /* FIXME!! */
+       /*
+        * Configuration via a conf file would be
+        * nice
+        */
+       profile_get_string(profile, "scratch_files",
+                                       "directory", 0, 0,
+                                       &tdb_dir);
+#endif
+       tdb_dir = getenv("MKE2FS_SCRATCH_DIR");
+       if (!tdb_dir) {
+               printf(_("MKE2FS_SCRATCH_DIR not configured\n"));
+               printf(_("Using /var/lib/e2fsprogs\n"));
+               tdb_dir="/var/lib/e2fsprogs";
+       }
+       if (access(tdb_dir, W_OK)) {
+               fprintf(stderr,
+                       _("Cannot create file under %s\n"),
+                       tdb_dir);
+               return EXT2_ET_INVALID_ARGUMENT;
+
+       }
+
+       /* FIXME!! Should we generate Unique file name ?? */
+       sprintf(tdb_file, "%s/mke2fs-XXXXXX", tdb_dir);
+
+       if (!access(tdb_file, F_OK)) {
+               fprintf(stderr,
+                       _("File exist %s\n"), tdb_file);
+               return EXT2_ET_INVALID_ARGUMENT;
+       }
+
+       set_undo_io_backup_file(tdb_file);
+       printf(_("previous filesystem detected; to undo "
+                "the mke2fs operation, please run the "
+                "command \n'undoe2fs %s %s' in order to recover\n\n"),
+                 tdb_file, name);
+       return 0;
+}
int main (int argc, char *argv[])
{
        errcode_t       retval = 0;
@@ -1543,7 +1629,17 @@ int main (int argc, char *argv[])
        io_ptr = test_io_manager;
        test_io_backing_manager = unix_io_manager;
#else
-       io_ptr = unix_io_manager;
+       if (fileystem_exist(device_name)) {
+
+               io_ptr = undo_io_manager;
+               set_undo_io_backing_manager(unix_io_manager);
+               retval = mke2fs_setup_tdb(device_name);
+               if (retval)
+                       exit(1);
+
+       } else {
+               io_ptr = unix_io_manager;
+       }
#endif

        /*
-
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