[Libguestfs] [PATCH v3 1/4] uuid: add support to change uuid of btrfs partition

[Chen Hanxiao]

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

Signed-off-by: Chen Hanxiao <chenhanxiao at cn.fujitsu.com>
---
v3: set errno as ENOTSUP when btrfstune -u is not available
v2: put btrfs operation back to daemon/btrfs.c
    move tests to tests/btrfs

 daemon/btrfs.c                 | 60 ++++++++++++++++++++++++++++++++++++++++++
 daemon/daemon.h                |  1 +
 daemon/uuids.c                 |  6 ++---
 tests/btrfs/test-btrfs-misc.pl | 17 ++++++++++++
 4 files changed, 80 insertions(+), 4 deletions(-)

diff --git a/daemon/btrfs.c b/daemon/btrfs.c
index 20e5e6b..80b7d80 100644
--- a/daemon/btrfs.c
+++ b/daemon/btrfs.c
@@ -790,6 +790,44 @@ 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_btrftune_uuid_opt (void)
+{
+  static int result = -1;
+  if (result != -1)
+    return result;
+
+  CLEANUP_FREE char *err = NULL;
+
+  int r = commandr (NULL, &err, str_btrfstune, 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)
 {
@@ -807,6 +845,28 @@ 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_btrftune_uuid_opt ();
+
+  if (has_uuid_opts <= 0) {
+    reply_with_error_errno (ENOTSUP, "btrfs filesystems' UUID cannot be changed");
+    return -1;
+  }
+
+  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)
diff --git a/daemon/daemon.h b/daemon/daemon.h
index 136e9a9..b74ba3c 100644
--- a/daemon/daemon.h
+++ b/daemon/daemon.h
@@ -268,6 +268,7 @@ 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);
diff --git a/daemon/uuids.c b/daemon/uuids.c
index 06b33e9..f98d8e5 100644
--- a/daemon/uuids.c
+++ b/daemon/uuids.c
@@ -110,10 +110,8 @@ 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",
diff --git a/tests/btrfs/test-btrfs-misc.pl b/tests/btrfs/test-btrfs-misc.pl
index 2fe7c59..b47caab 100755
--- a/tests/btrfs/test-btrfs-misc.pl
+++ b/tests/btrfs/test-btrfs-misc.pl
@@ -20,6 +20,7 @@
 
 use strict;
 use warnings;
+use Errno;
 
 use Sys::Guestfs;
 
@@ -47,5 +48,21 @@ 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");
+};
+# FIXME: ignore ESRCH
+my $err = $g->last_errno ();
+
+if ($err == 0) {
+    my $uuid = $g->vfs_uuid ("/dev/sda1");
+    die "unexpected uuid expecting
+     '12345678-1234-1234-1234-123456789012' but got '$uuid'"
+    unless $uuid eq "12345678-1234-1234-1234-123456789012";
+} elsif ($err == Errno::ENOTSUP()) {
+    warn "$0: skipping test for btrfs UUID change feature is not available\n";
+}
+
 $g->shutdown ();
 $g->close ();
-- 
2.1.0