wipefs: improve -a, use blkid_do_wipe()

Some filesystems (e.g. FAT) is possible to detect in many ways -- for
example if a magic string is stored on more places on the device. The
current implementation always removes from the device only the firstly
detected possibility.

 # wipefs /dev/sdb1
 offset               type
 ----------------------------------------------------------------
 0x36                 vfat   [filesystem]
                      UUID:  D203-A7F4

 # wipefs -a /dev/sdb1
 8 bytes [46 41 54 31 36 20 20 20] erased at offset 0x36 (vfat)

 # wipefs /dev/sdb1
 offset               type
 ----------------------------------------------------------------
 0x0                  vfat   [filesystem]
                      UUID:  D203-A7F4

This patch fixes this issue:

 # wipefs -a /dev/sdb1
 8 bytes were erased at offset 0x00000036 (vfat): 46 41 54 31 36 20 20 20
 1 bytes were erased at offset 0x00000000 (vfat): eb
 2 bytes were erased at offset 0x000001fe (vfat): 55 aa

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

1 files changed, 92 insertions, 66 deletions

diff --git a/misc-utils/wipefs.c b/misc-utils/wipefs.c
index 58fc03d00..1cd3159d1 100644
--- a/misc-utils/wipefs.c
+++ b/misc-utils/wipefs.c
@@ -49,6 +49,8 @@ struct wipe_desc {
 	char		*label;		/* FS label */
 	char		*uuid;		/* FS uuid */
 
+	int		on_disk;
+
 	struct wipe_desc	*next;
 };
 
@@ -138,7 +140,7 @@ add_offset(struct wipe_desc *wp0, loff_t offset, int zap)
 }
 
 static struct wipe_desc *
-get_offset_from_probe(struct wipe_desc *wp, blkid_probe pr, int zap)
+get_desc_for_probe(struct wipe_desc *wp, blkid_probe pr)
 {
 	const char *off, *type, *usage, *mag;
 	size_t len;
@@ -151,12 +153,13 @@ get_offset_from_probe(struct wipe_desc *wp, blkid_probe pr, int zap)
 		loff_t offset = strtoll(off, NULL, 10);
 		const char *p;
 
-		wp = add_offset(wp, offset, zap);
+		wp = add_offset(wp, offset, 0);
 		if (!wp)
 			return NULL;
 
 		wp->usage = xstrdup(usage);
 		wp->type = xstrdup(type);
+		wp->on_disk = 1;
 
 		wp->magic = xmalloc(len);
 		memcpy(wp->magic, mag, len);
@@ -172,18 +175,28 @@ get_offset_from_probe(struct wipe_desc *wp, blkid_probe pr, int zap)
 	return wp;
 }
 
-static struct wipe_desc *
-read_offsets(struct wipe_desc *wp, const char *fname, int zap)
+static blkid_probe
+new_probe(const char *devname, int mode)
 {
 	blkid_probe pr;
 	int rc;
 
-	if (!fname)
+	if (!devname)
 		return NULL;
 
-	pr = blkid_new_probe_from_filename(fname);
+	if (mode) {
+		int fd = open(devname, mode);
+		if (fd < 0)
+			goto error;
+
+		pr = blkid_new_probe();
+		if (pr && blkid_probe_set_device(pr, fd, 0, 0))
+			goto error;
+	} else
+		pr = blkid_new_probe_from_filename(devname);
+
 	if (!pr)
-		errx(EXIT_FAILURE, _("error: %s: probing initialization failed"), fname);
+		goto error;
 
 	blkid_probe_enable_superblocks(pr, 0);	/* enabled by default ;-( */
 
@@ -195,7 +208,7 @@ read_offsets(struct wipe_desc *wp, const char *fname, int zap)
 		const char *type = NULL;
 		blkid_probe_lookup_value(pr, "PTTYPE", &type, NULL);
 		warnx(_("WARNING: %s: appears to contain '%s' "
-				"partition table"), fname, type);
+				"partition table"), devname, type);
 	}
 
 	blkid_probe_enable_superblocks(pr, 1);
@@ -203,8 +216,22 @@ read_offsets(struct wipe_desc *wp, const char *fname, int zap)
 			BLKID_SUBLKS_TYPE | BLKID_SUBLKS_USAGE |
 			BLKID_SUBLKS_LABEL | BLKID_SUBLKS_UUID);
 
+	return pr;
+error:
+	err(EXIT_FAILURE, _("error: %s: probing initialization failed"), devname);
+	return NULL;
+}
+
+static struct wipe_desc *
+read_offsets(struct wipe_desc *wp, const char *devname)
+{
+	blkid_probe pr = new_probe(devname, 0);
+
+	if (!pr)
+		return NULL;
+
 	while (blkid_do_probe(pr) == 0) {
-		wp = get_offset_from_probe(wp, pr, zap);
+		wp = get_desc_for_probe(wp, pr);
 		if (!wp)
 			break;
 	}
@@ -213,60 +240,54 @@ read_offsets(struct wipe_desc *wp, const char *fname, int zap)
 	return wp;
 }
 
-static int
-do_wipe_offset(int fd, struct wipe_desc *wp, const char *fname, int noact)
+static struct wipe_desc *
+do_wipe(struct wipe_desc *wp, const char *devname, int noact, int all)
 {
-	char buf[BUFSIZ];
-	off_t l;
-	size_t i, len;
-
-	if (!wp->type) {
-		warnx(_("no magic string found at offset "
-			"0x%jx -- ignored"), wp->offset);
-		return 0;
-	}
-
-	l = lseek(fd, wp->offset, SEEK_SET);
-	if (l == (off_t) -1)
-		err(EXIT_FAILURE, _("%s: failed to seek to offset 0x%jx"),
-				fname, wp->offset);
-
-	len = wp->len > sizeof(buf) ? sizeof(buf) : wp->len;
-
-	memset(buf, 0, len);
-	if (noact == 0 && write_all(fd, buf, len))
-		err(EXIT_FAILURE, _("%s: write failed"), fname);
+	blkid_probe pr = new_probe(devname, O_RDWR);
+	struct wipe_desc *w;
 
-	printf(_("%zd bytes were erased at offset 0x%jx (%s)\nthey were: "),
-	       wp->len, wp->offset, wp->type);
+	if (!pr)
+		return NULL;
 
-	for (i = 0; i < len; i++) {
-		printf("%02x", wp->magic[i]);
-		if (i + 1 < len)
-			fputc(' ', stdout);
+	while (blkid_do_probe(pr) == 0) {
+		w = get_desc_for_probe(wp, pr);
+		if (!w)
+			break;
+		wp = w;
+		if (!wp->on_disk)
+			continue;
+		wp->zap = all ? 1 : wp->zap;
+		if (!wp->zap)
+			continue;
+
+		if (blkid_do_wipe(pr, noact))
+			warn(_("failed to erase %s magic string at offset 0x%08jx"),
+			     wp->type, wp->offset);
+		else {
+			size_t i;
+
+			printf(_("%zd bytes were erased at offset 0x%08jx (%s): "),
+				wp->len, wp->offset, wp->type);
+
+			for (i = 0; i < wp->len; i++) {
+				printf("%02x", wp->magic[i]);
+				if (i + 1 < wp->len)
+					fputc(' ', stdout);
+			}
+			putchar('\n');
+		}
 	}
 
-	printf("\n");
-	return 0;
-}
-
-static int
-do_wipe(struct wipe_desc *wp, const char *fname, int noact)
-{
-	int fd;
-
-	fd = open(fname, O_WRONLY);
-	if (fd < 0)
-		err(EXIT_FAILURE, _("%s: open failed"), fname);
-
-	while (wp) {
-		if (wp->zap)
-			do_wipe_offset(fd, wp, fname, noact);
-		wp = wp->next;
+	for (w = wp; w != NULL; w = w->next) {
+		if (!w->on_disk)
+			warnx(_("offset 0x%jx not found"), w->offset);
 	}
 
-	close(fd);
-	return 0;
+	fsync(blkid_probe_get_fd(pr));
+	close(blkid_probe_get_fd(pr));
+	blkid_free_probe(pr);
+
+	return wp;
 }
 
 static void
@@ -323,7 +344,7 @@ main(int argc, char **argv)
 {
 	struct wipe_desc *wp = NULL;
 	int c, all = 0, has_offset = 0, noact = 0, mode = 0;
-	const char *fname;
+	const char *devname;
 
 	static const struct option longopts[] = {
 	    { "all",       0, 0, 'a' },
@@ -372,20 +393,25 @@ main(int argc, char **argv)
 	if (optind == argc)
 		usage(stderr);
 
-	fname = argv[optind++];
+	devname = argv[optind++];
 
 	if (optind != argc)
 		errx(EXIT_FAILURE, _("only one device as argument is currently supported."));
 
-	wp = read_offsets(wp, fname, all);
-
-	if (wp) {
-		if (has_offset || all)
-			do_wipe(wp, fname, noact);
-		else
+	if (!all && !has_offset) {
+		/*
+		 * Print only
+		 */
+		wp = read_offsets(wp, devname);
+		if (wp)
 			print_all(wp, mode);
-
-		free_wipe(wp);
+	} else {
+		/*
+		 * Erase
+		 */
+		wp = do_wipe(wp, devname, noact, all);
 	}
+
+	free_wipe(wp);
 	return EXIT_SUCCESS;
 }