fdisk: add --wipe-partitions=auto|never|default

The option allows to remove filesystes/RAIDs from newly created
partitions before the partition table is updated (and partition
device created).

The default is "auto" in this case wipe is enabled in interactive mode
only and user's confirmation (yes/no dialog) is required. Note that
keep filesystem signature on partition is pretty valid use-case, so we
don't erase anything by default.

Signed-off-by: Karel Zak <kzak@redhat.com>

disk-utils/fdisk-menu.c

@@ -516,6 +516,37 @@ done:
 	return rc;
 }
 
+static int ask_for_wipe(struct fdisk_context *cxt, size_t partno)
+{
+	struct fdisk_partition *tmp = NULL;
+	char *fstype = NULL;
+	int rc, yes = 0;
+
+	rc = fdisk_get_partition(cxt, partno, &tmp);
+	if (rc)
+		goto done;
+
+	rc = fdisk_partition_to_string(tmp, cxt, FDISK_FIELD_FSTYPE, &fstype);
+	if (rc || fstype == NULL)
+		goto done;
+
+	fdisk_warnx(cxt, _("Partition #%zu contains a %s signature."), partno + 1, fstype);
+
+	if (pwipemode == WIPEMODE_AUTO && isatty(STDIN_FILENO))
+		fdisk_ask_yesno(cxt, _("Do you want to remove the signature?"), &yes);
+	else if (pwipemode == WIPEMODE_ALWAYS)
+		yes = 1;
+
+	if (yes) {
+		fdisk_info(cxt, _("The signature will be removed by a write command."));
+		rc = fdisk_wipe_partition(cxt, partno, TRUE);
+	}
+done:
+	fdisk_unref_partition(tmp);
+	free(fstype);
+	return rc;
+}
+
 /*
  * Basic fdisk actions
  */
@@ -610,8 +641,13 @@ static int generic_menu_cb(struct fdisk_context **cxt0,
 		list_partition_types(cxt);
 		break;
 	case 'n':
-		rc = fdisk_add_partition(cxt, NULL, NULL);
+	{
+		size_t partno;
+		rc = fdisk_add_partition(cxt, NULL, &partno);
+		if (!rc)
+			rc = ask_for_wipe(cxt, partno);
 		break;
+	}
 	case 't':
 		change_partition_type(cxt);
 		break;

disk-utils/fdisk.8

@@ -129,6 +129,18 @@ before a new partition table is created.  See also
 .BR wipefs (8)
 command.
 
+.TP
+\fB\-W\fR, \fB\-\-wipe-partition\fR \fIwhen\fR
+Wipe filesystem, RAID and partition-table signatures from a newly created
+partitions, in order to avoid possible collisions.  The argument \fIwhen\fR can
+be \fBauto\fR, \fBnever\fR or \fBalways\fR.  When this option is not given, the
+default is \fBauto\fR, in which case signatures are wiped only when in
+interactive mode and after confirmation by user.  In all cases detected
+signatures are reported by warning messages before a new partition is
+created.  See also
+.BR wipefs (8)
+command.
+
 .TP
 \fB\-V\fR, \fB\-\-version\fR
 Display version information and exit.

disk-utils/fdisk.c

@@ -49,6 +49,8 @@
 # include <linux/blkpg.h>
 #endif
 
+int pwipemode = WIPEMODE_AUTO;
+
 /*
  * fdisk debug stuff (see fdisk.h and include/debug.h)
  */
@@ -741,6 +743,7 @@ static void __attribute__ ((__noreturn__)) usage(FILE *out)
 	fputs(_(" -s, --getsz                   display device size in 512-byte sectors [DEPRECATED]\n"), out);
 	fputs(_("     --bytes                   print SIZE in bytes rather than in human readable format\n"), out);
 	fputs(_(" -w, --wipe <mode>             wipe signatures (auto, always or never)\n"), out);
+	fputs(_(" -W, --wipe-partitions <mode>  wipe signatures from new partitions (auto, always or never)\n"), out);
 
 	fputs(USAGE_SEPARATOR, out);
 	fputs(_(" -C, --cylinders <number>      specify the number of cylinders\n"), out);
@@ -791,6 +794,7 @@ int main(int argc, char **argv)
 		{ "output",         no_argument,       NULL, 'o' },
 		{ "protect-boot",   no_argument,       NULL, 'B' },
 		{ "wipe",           required_argument, NULL, 'w' },
+		{ "wipe-partitions",required_argument, NULL, 'W' },
 		{ NULL, 0, NULL, 0 }
 	};
 
@@ -809,7 +813,7 @@ int main(int argc, char **argv)
 
 	fdisk_set_ask(cxt, ask_callback, NULL);
 
-	while ((c = getopt_long(argc, argv, "b:Bc::C:hH:lL::o:sS:t:u::vVw:",
+	while ((c = getopt_long(argc, argv, "b:Bc::C:hH:lL::o:sS:t:u::vVw:W:",
 				longopts, NULL)) != -1) {
 		switch (c) {
 		case 'b':
@@ -905,6 +909,11 @@ int main(int argc, char **argv)
 			if (wipemode < 0)
 				errx(EXIT_FAILURE, _("unsupported wipe mode"));
 			break;
+		case 'W':
+			pwipemode = wipemode_from_string(optarg);
+			if (pwipemode < 0)
+				errx(EXIT_FAILURE, _("unsupported wipe mode"));
+			break;
 		case 'h':
 			usage(stdout);
 		case OPT_BYTES:

disk-utils/fdisk.h

@@ -24,6 +24,8 @@
 #define FDISKPROG_DEBUG_ASK	(1 << 5)
 #define FDISKPROG_DEBUG_ALL	0xFFFF
 
+extern int pwipemode;
+
 UL_DEBUG_DECLARE_MASK(fdisk);
 #define DBG(m, x)       __UL_DBG(fdisk, FDISKPROG_DEBUG_, m, x)
 #define ON_DBG(m, x)    __UL_DBG_CALL(fdisk, FDISKPROG_DEBUG_, m, x)