daemon: Call wipefs before mkfs to work around pathological behaviour in btrfs.

See: RHBZ#907554, http://www.spinics.net/lists/linux-btrfs/msg21197.html

daemon/btrfs.c

@@ -193,6 +193,9 @@ do_mkfs_btrfs (char *const *devices,
 
   ADD_ARG (argv, i, NULL);
 
+  for (j = 0; j < nr_devices; ++j)
+    wipe_device_before_mkfs (devices[j]);
+
   r = commandv (NULL, &err, argv);
   if (r == -1) {
     reply_with_error ("%s: %s", devices[0], err);

daemon/daemon.h

@@ -186,6 +186,9 @@ extern int lv_canonical (const char *device, char **ret);
 /*-- in lvm-filter.c --*/
 extern void copy_lvm (void);
 
+/*-- in zero.c --*/
+extern void wipe_device_before_mkfs (const char *device);
+
 /*-- in proto.c --*/
 extern void main_loop (int sock) __attribute__((noreturn));
 

daemon/ext2.c

@@ -306,6 +306,8 @@ do_mke2journal (int blocksize, const char *device)
   char blocksize_s[32];
   snprintf (blocksize_s, sizeof blocksize_s, "%d", blocksize);
 
+  wipe_device_before_mkfs (device);
+
   r = command (NULL, &err,
                str_mke2fs, "-F", "-O", "journal_dev", "-b", blocksize_s,
                device, NULL);
@@ -332,6 +334,8 @@ do_mke2journal_L (int blocksize, const char *label, const char *device)
   char blocksize_s[32];
   snprintf (blocksize_s, sizeof blocksize_s, "%d", blocksize);
 
+  wipe_device_before_mkfs (device);
+
   r = command (NULL, &err,
                str_mke2fs, "-F", "-O", "journal_dev", "-b", blocksize_s,
                "-L", label,
@@ -353,6 +357,8 @@ do_mke2journal_U (int blocksize, const char *uuid, const char *device)
   char blocksize_s[32];
   snprintf (blocksize_s, sizeof blocksize_s, "%d", blocksize);
 
+  wipe_device_before_mkfs (device);
+
   r = command (NULL, &err,
                str_mke2fs, "-F", "-O", "journal_dev", "-b", blocksize_s,
                "-U", uuid,
@@ -379,6 +385,8 @@ do_mke2fs_J (const char *fstype, int blocksize, const char *device,
   char jdev[len+32];
   snprintf (jdev, len+32, "device=%s", journal);
 
+  wipe_device_before_mkfs (device);
+
   r = command (NULL, &err,
                str_mke2fs, "-F", "-t", fstype, "-J", jdev, "-b", blocksize_s,
                device, NULL);
@@ -410,6 +418,8 @@ do_mke2fs_JL (const char *fstype, int blocksize, const char *device,
   char jdev[len+32];
   snprintf (jdev, len+32, "device=LABEL=%s", label);
 
+  wipe_device_before_mkfs (device);
+
   r = command (NULL, &err,
                str_mke2fs, "-F", "-t", fstype, "-J", jdev, "-b", blocksize_s,
                device, NULL);
@@ -435,6 +445,8 @@ do_mke2fs_JU (const char *fstype, int blocksize, const char *device,
   char jdev[len+32];
   snprintf (jdev, len+32, "device=UUID=%s", uuid);
 
+  wipe_device_before_mkfs (device);
+
   r = command (NULL, &err,
                str_mke2fs, "-F", "-t", fstype, "-J", jdev, "-b", blocksize_s,
                device, NULL);
@@ -1128,6 +1140,8 @@ do_mke2fs (const char *device,               /* 0 */
 
   ADD_ARG (argv, i, NULL);
 
+  wipe_device_before_mkfs (device);
+
   r = commandv (NULL, &err, argv);
   if (r == -1) {
     reply_with_error ("%s: %s", device, err);

daemon/mkfs.c

@@ -184,6 +184,8 @@ do_mkfs (const char *fstype, const char *device, int blocksize,
   ADD_ARG (argv, i, device);
   ADD_ARG (argv, i, NULL);
 
+  wipe_device_before_mkfs (device);
+
   r = commandv (NULL, &err, argv);
   if (r == -1) {
     reply_with_error ("%s: %s: %s", fstype, device, err);

daemon/swap.c

@@ -91,6 +91,8 @@ do_mkswap (const char *device, const char *label, const char *uuid)
   ADD_ARG (argv, i, device);
   ADD_ARG (argv, i, NULL);
 
+  wipe_device_before_mkfs (device);
+
   r = commandv (NULL, &err, argv);
   if (r == -1) {
     reply_with_error ("%s: %s", device, err);

daemon/zero.c

@@ -337,3 +337,32 @@ do_zero_free_space (const char *dir)
 
   return 0;
 }
+
+/* Internal function used to wipe disks before we do 'mkfs'-type
+ * operations on them.  For the rationale see RHBZ#889888 and
+ * RHBZ#907554.
+ *
+ * Note this is really destructive, so only call it just before doing
+ * the 'mkfs' operation (ie. after doing as much pre-checking as
+ * possible).  Otherwise you could end up with a 'mkfs' operation
+ * failing with an error but still wiping data.
+ */
+void
+wipe_device_before_mkfs (const char *device)
+{
+  int r;
+
+  r = command (NULL, NULL, "wipefs", "-a", "--force", device, NULL);
+  if (r == 0)
+    return;
+
+  r = command (NULL, NULL, "wipefs", "-a", device, NULL);
+  if (r == 0)
+    return;
+
+  /* XXX We could fall back to overwriting bits of disk here, but if
+   * they don't have working wipefs, it seems unlikely they are using
+   * btrfs which is what mostly causes this problem.  See:
+   * http://www.spinics.net/lists/linux-btrfs/msg21197.html
+   */
+}