uuid: add support to change uuid of btrfs partition

btrfs-progs v4.1 add support to change uuid of btrfs fs.

Signed-off-by: Chen Hanxiao <chenhanxiao@cn.fujitsu.com>

daemon/btrfs.c

@@ -797,6 +797,44 @@ do_btrfs_device_delete (char *const *devices, const char *fs)
   return 0;
 }
 
+
+/* btrfstune command add two new options
+ * -U UUID      change fsid to UUID
+ * -u           change fsid, use a random one
+ * since v4.1
+ * We could check wheter 'btrfstune' support
+ * '-u' and '-U UUID' option by checking the output of
+ * 'btrfstune' command.
+ */
+static int
+test_btrfstune_uuid_opt (void)
+{
+  static int result = -1;
+  if (result != -1)
+    return result;
+
+  CLEANUP_FREE char *err = NULL;
+
+  int r = commandr (NULL, &err, str_btrfstune, "--help", NULL);
+
+  if (r == -1) {
+    reply_with_error ("btrfstune: %s", err);
+    return -1;
+  }
+
+  /* FIXME currently btrfstune do not support '--help'.
+   * If got an invalid options, it will print its usage
+   * in stderr.
+   * We had to check it there.
+   */
+  if (strstr (err, "-U") == NULL || strstr (err, "-u") == NULL)
+    result = 0;
+  else
+    result = 1;
+
+  return result;
+}
+
 int
 do_btrfs_set_seeding (const char *device, int svalue)
 {
@@ -814,6 +852,26 @@ do_btrfs_set_seeding (const char *device, int svalue)
   return 0;
 }
 
+int
+btrfs_set_uuid (const char *device, const char *uuid)
+{
+  CLEANUP_FREE char *err = NULL;
+  int r;
+  int has_uuid_opts = test_btrfstune_uuid_opt ();
+
+  if (has_uuid_opts <= 0)
+    NOT_SUPPORTED(-1, "btrfs filesystems' UUID cannot be changed");
+
+  r = commandr (NULL, &err, str_btrfstune, "-f", "-U", uuid, device, NULL);
+
+  if (r == -1) {
+    reply_with_error ("%s: %s", device, err);
+    return -1;
+  }
+
+  return 0;
+}
+
 /* Takes optional arguments, consult optargs_bitmask. */
 int
 do_btrfs_fsck (const char *device, int64_t superblock, int repair)

daemon/daemon.h

@@ -273,6 +273,7 @@ extern char *debug_bmap_device (const char *subcmd, size_t argc, char *const *co
 
 /*-- in btrfs.c --*/
 extern char *btrfs_get_label (const char *device);
+extern int btrfs_set_uuid (const char *device, const char *uuid);
 
 /*-- in ntfs.c --*/
 extern char *ntfs_get_label (const char *device);

daemon/uuids.c

@@ -90,10 +90,8 @@ do_set_uuid (const char *device, const char *uuid)
   else if (STREQ (vfs_type, "swap"))
     r = swapuuid (device, uuid);
 
-  else if (STREQ (vfs_type, "btrfs")) {
-    reply_with_error ("btrfs filesystems' UUID cannot be changed");
-    r = -1;
-  }
+  else if (STREQ (vfs_type, "btrfs"))
+    r = btrfs_set_uuid (device, uuid);
 
   else {
     reply_with_error ("don't know how to set the UUID for '%s' filesystems",

tests/btrfs/test-btrfs-misc.pl

@@ -20,6 +20,7 @@
 
 use strict;
 use warnings;
+use Errno;
 
 use Sys::Guestfs;
 
@@ -47,5 +48,24 @@ my $label = $g->vfs_label ("/dev/sda1");
 die "unexpected label: expecting 'newlabel' but got '$label'"
     unless $label eq "newlabel";
 
+# Setting btrfs UUID
+eval {
+    $g->set_uuid ("/dev/sda1", "12345678-1234-1234-1234-123456789012");
+};
+
+if ($@) {
+    my $err = $g->last_errno ();
+    if ($err == Errno::ENOTSUP()) {
+        warn "$0: skipping test for btrfs UUID change feature is not available";
+    } else {
+        die $@;
+    }
+} else {
+    my $uuid = $g->vfs_uuid ("/dev/sda1");
+    die "unexpected uuid expecting
+      '12345678-1234-1234-1234-123456789012' but got '$uuid'"
+    unless $uuid eq "12345678-1234-1234-1234-123456789012";
+}
+
 $g->shutdown ();
 $g->close ();