From: Karel Zak <kzak@redhat.com>
Date: Thu, 1 Mar 2012 13:24:04 +0000 (+0100)
Subject: libblkid: properly reset chain in probe_do_wipe()
X-Git-Tag: v2.22-rc1~731
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=89d39d22170b7c5b264e270ce706a0d25f2e0d36;p=thirdparty%2Futil-linux.git

libblkid: properly reset chain in probe_do_wipe()

The command wipefs is not able to remove all signatures from the
device if the first detected signature is linux raid. The another
superblock signatures are ignored. For example:

  # pvcreate /dev/sdb1
  # mdadm --create md8 --metadata=0.90 --chunk=64 --level=0 \
        --raid-devices=2 /dev/sdb1 /dev/sdb2

  # wipefs -a /dev/sdb1

will delete the linux raid signature only.

Reported-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Karel Zak <kzak@redhat.com>
---

diff --git a/libblkid/src/probe.c b/libblkid/src/probe.c
index 763f75ca01..6bd69d39ed 100644
--- a/libblkid/src/probe.c
+++ b/libblkid/src/probe.c
@@ -388,6 +388,7 @@ void blkid_reset_probe(blkid_probe pr)
 		return;
 
 	blkid_probe_reset_vals(pr);
+	blkid_probe_set_wiper(pr, 0, 0);
 
 	pr->cur_chain = NULL;
 
@@ -989,7 +990,7 @@ int blkid_do_wipe(blkid_probe pr, int dryrun)
 		len = sizeof(buf);
 
 	DBG(DEBUG_LOWPROBE, printf(
-	    "wiping [offset=0x%jx, len=%zd, chain=%s, idx=%d, dryrun=%s]\n",
+	    "do_wipe [offset=0x%jx, len=%zd, chain=%s, idx=%d, dryrun=%s]\n",
 	    offset, len, chn->driver->name, chn->idx, dryrun ? "yes" : "not"));
 
 	l = lseek(fd, offset, SEEK_SET);
@@ -1008,10 +1009,23 @@ int blkid_do_wipe(blkid_probe pr, int dryrun)
 		if (chn->idx >= 0) {
 			chn->idx--;
 			DBG(DEBUG_LOWPROBE,
-				printf("wipe: moving %s chain index to %d\n",
+				printf("do_wipe: moving %s chain index to %d\n",
 				chn->driver->name,
 				chn->idx));
 		}
+		if (chn->idx == -1) {
+			/* blkid_do_probe() goes to the next chain if the index
+			 * of the current chain is -1, so we have to set the
+			 * chain pointer to the previos chain.
+			 */
+			size_t idx = chn->driver->id > 0 ?
+					chn->driver->id - 1 : 0;
+
+			if (idx > 0)
+				pr->cur_chain = &pr->chains[idx];
+			else if (idx == 0)
+				pr->cur_chain = NULL;
+		}
 	}
 	return 0;
 }
@@ -1579,8 +1593,9 @@ size_t blkid_rtrim_whitespace(unsigned char *str)
  * for later resolution to conflicts between superblocks.
  *
  * For example we found valid LVM superblock, LVM wipes 8KiB at the begin of
- * the device. If we found another signature (for example MBR) this wiped area
- * then the signature has been added later and LVM superblock should be ignore.
+ * the device. If we found another signature (for example MBR) within the
+ * wiped area then the signature has been added later and LVM superblock
+ * should be ignore.
  *
  * Note that this heuristic is not 100% reliable, for example "pvcreate --zero
  * n" allows to keep the begin of the device unmodified. It's probably better
@@ -1588,6 +1603,16 @@ size_t blkid_rtrim_whitespace(unsigned char *str)
  * than for conflicts between filesystem superblocks -- existence of unwanted
  * partition table is very unusual, because PT is pretty visible (parsed and
  * interpreted by kernel).
+ *
+ * Note that we usually expect only one signature on the device, it means that
+ * we have to remember only one wiped area from previously successfully
+ * detected signature.
+ *
+ * blkid_probe_set_wiper() -- defines wiped area (e.g. LVM)
+ * blkid_probe_use_wiper() -- try to use area (e.g. MBR)
+ *
+ * Note that there is not relation between _wiper and blkid_to_wipe().
+ *
  */
 void blkid_probe_set_wiper(blkid_probe pr, blkid_loff_t off, blkid_loff_t size)
 {
@@ -1638,12 +1663,17 @@ int blkid_probe_is_wiped(blkid_probe pr, struct blkid_chain **chn,
 	return 0;
 }
 
+/*
+ *  Try to use any area -- if the area has been previously wiped then the
+ *  previous probing result should be ignored (reseted).
+ */
 void blkid_probe_use_wiper(blkid_probe pr, blkid_loff_t off, blkid_loff_t size)
 {
 	struct blkid_chain *chn = NULL;
 
 	if (blkid_probe_is_wiped(pr, &chn, off, size) && chn) {
-		DBG(DEBUG_LOWPROBE, printf("wiped area detected -- ignore previous results\n"));
+		DBG(DEBUG_LOWPROBE, printf("previously wiped area modified "
+				       " -- ignore previous results\n"));
 		blkid_probe_set_wiper(pr, 0, 0);
 		blkid_probe_chain_reset_vals(pr, chn);
 	}