mke2fs: optionally create undo file

Provide the user with an option to create an undo file so that they
can roll back a failed tuning operation.  Previously, one would be
created if force_undo was set in the configuration file and a bunch of
(undocumented) conditions were met.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/misc/mke2fs.8.in b/misc/mke2fs.8.in
index aeb5caf..3230f65 100644 (file)
--- a/misc/mke2fs.8.in
+++ b/misc/mke2fs.8.in
@@ -117,6 +117,10 @@ mke2fs \- create an ext2/ext3/ext4 filesystem
 .B \-e
 .I errors-behavior
 ]
+[
+.B \-z
+.I undo_file
+]
 .I device
 [
 .I fs-size
@@ -738,6 +742,17 @@ Verbose execution.
 Print the version number of
 .B mke2fs
 and exit.
+.TP
+.BI \-z " undo_file"
+Before overwriting a file system block, write the old contents of the block to
+an undo file.  This undo file can be used with e2undo(8) to restore the old
+contents of the file system should something go wrong.  If the empty string is
+passed as the undo_file argument, the undo file will be written to a file named
+mke2fs-\fIdevice\fR.e2undo in the directory specified via the
+\fIE2FSPROGS_UNDO_DIR\fR environment variable or the \fIundo_dir\fR directive
+in the configuration file.
+
+WARNING: The undo file cannot be used to recover from a power or system crash.
 .SH ENVIRONMENT
 .TP
 .BI MKE2FS_SYNC

diff --git a/misc/mke2fs.c b/misc/mke2fs.c
index 6883103..cd6e614 100644 (file)
--- a/misc/mke2fs.c
+++ b/misc/mke2fs.c
@@ -110,6 +110,7 @@ char *journal_device;
 static int sync_kludge;        /* Set using the MKE2FS_SYNC env. option */
 char **fs_types;
 const char *root_dir;  /* Copy files from the specified directory */
+static char *undo_file;
 
 static profile_t       profile;
 
@@ -129,7 +130,8 @@ static void usage(void)
        "[-M last-mounted-directory]\n\t[-O feature[,...]] "
        "[-r fs-revision] [-E extended-option[,...]]\n"
        "\t[-t fs-type] [-T usage-type ] [-U UUID] [-e errors_behavior]"
-       "[-jnqvDFKSV] device [blocks-count]\n"),
+       "[-z undo_file]\n"
+       "\t[-jnqvDFKSV] device [blocks-count]\n"),
                program_name);
        exit(1);
 }
@@ -1552,7 +1554,7 @@ profile_error:
        }
 
        while ((c = getopt (argc, argv,
-                   "b:ce:g:i:jl:m:no:qr:s:t:d:vC:DE:FG:I:J:KL:M:N:O:R:ST:U:V")) != EOF) {
+                   "b:ce:g:i:jl:m:no:qr:s:t:d:vC:DE:FG:I:J:KL:M:N:O:R:ST:U:Vz:")) != EOF) {
                switch (c) {
                case 'b':
                        blocksize = parse_num_blocks2(optarg, -1);
@@ -1775,6 +1777,9 @@ profile_error:
                        /* Print version number and exit */
                        show_version_only++;
                        break;
+               case 'z':
+                       undo_file = optarg;
+                       break;
                default:
                        usage();
                }
@@ -2493,6 +2498,19 @@ static int mke2fs_setup_tdb(const char *name, io_manager *io_ptr)
        char *dev_name, *tmp_name;
        int free_tdb_dir = 0;
 
+       /* (re)open a specific undo file */
+       if (undo_file && undo_file[0] != 0) {
+               set_undo_io_backing_manager(*io_ptr);
+               *io_ptr = undo_io_manager;
+               retval = set_undo_io_backup_file(undo_file);
+               if (retval)
+                       goto err;
+               printf(_("Overwriting existing filesystem; this can be undone "
+                        "using the command:\n"
+                        "    e2undo %s %s\n\n"), undo_file, name);
+               return 0;
+       }
+
        /*
         * Configuration via a conf file would be
         * nice
@@ -2547,6 +2565,7 @@ errout:
        if (free_tdb_dir)
                free(tdb_dir);
        free(tdb_file);
+err:
        com_err(program_name, retval, "%s",
                _("while trying to setup undo file\n"));
        return retval;
@@ -2718,7 +2737,7 @@ int main (int argc, char *argv[])
 #endif
                io_ptr = unix_io_manager;
 
-       if (should_do_undo(device_name)) {
+       if (undo_file != NULL || should_do_undo(device_name)) {
                retval = mke2fs_setup_tdb(device_name, &io_ptr);
                if (retval)
                        exit(1);