[Libguestfs] [PATCH v2 1/5] uuid: add support to change uuid of btrfs partition

[Pino Toscano]

In data mercoledì 24 giugno 2015 15:54:03, Chen Hanxiao ha scritto:
> btrfs-progs v4.1 add support to change uuid of btrfs fs.
> 
> Signed-off-by: Chen Hanxiao <chenhanxiao at cn.fujitsu.com>
> ---
> 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                 |  9 +++++--
>  tests/btrfs/test-btrfs-misc.pl |  6 +++++
>  4 files changed, 74 insertions(+), 2 deletions(-)
> 
> diff --git a/daemon/btrfs.c b/daemon/btrfs.c
> index 20e5e6b..b82c1b9 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
> +btrfstune_set_uuid (const char *device, const char *uuid)

Call it btrfs_set_uuid please, as the fact that it uses btrfstune is an
implementation detail of it.

> +{
> +  CLEANUP_FREE char *err = NULL;
> +  int r;
> +  int has_uuid_opts = test_btrftune_uuid_opt ();
> +
> +  if (has_uuid_opts == 0) {

Check for <= 0 here, to consider errors in test_btrftune_uuid_opt
on the safe side.

> +    reply_with_error ("btrfstune do not support '-u'");

 reply_with_error ("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..ee0c96f 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 btrfstune_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..f7791ab 100644
> --- a/daemon/uuids.c
> +++ b/daemon/uuids.c
> @@ -91,6 +91,12 @@ swapuuid (const char *device, const char *uuid)
>    return 0;
>  }
>  
> +static int
> +btrfsuuid (const char *device, const char *uuid)
> +{
> +  return btrfstune_set_uuid (device, uuid);
> +}

What is this wrapper for? Just call btrfs_set_uuid below.

>  int
>  do_set_uuid (const char *device, const char *uuid)
>  {
> @@ -111,8 +117,7 @@ do_set_uuid (const char *device, const char *uuid)
>      r = swapuuid (device, uuid);
>  
>    else if (STREQ (vfs_type, "btrfs")) {
> -    reply_with_error ("btrfs filesystems' UUID cannot be changed");
> -    r = -1;
> +    r = btrfsuuid (device, uuid);
>    }

Minor style note: curly brackets can be removed now.

>    else {
> diff --git a/tests/btrfs/test-btrfs-misc.pl b/tests/btrfs/test-btrfs-misc.pl
> index 2fe7c59..cd60990 100755
> --- a/tests/btrfs/test-btrfs-misc.pl
> +++ b/tests/btrfs/test-btrfs-misc.pl
> @@ -47,5 +47,11 @@ my $label = $g->vfs_label ("/dev/sda1");
>  die "unexpected label: expecting 'newlabel' but got '$label'"
>      unless $label eq "newlabel";
>  
> +# Setting btrfs UUID
> +$g->set_uuid ("/dev/sda1", "12345678-1234-1234-1234-123456789012");
> +my $uuid = $g->vfs_uuid ("/dev/sda1");
> +die "unexpected label: expecting 'newlabel' but got '$uuid'"
> +    unless $uuid eq "12345678-1234-1234-1234-123456789012";
> +

Ignoring the "newlabel" copy&paste error: this code has the same issue
as the old test added to the action tests in generator/actions.ml.
That is, if btrfs-tools < 4.1 is used, then the test will fail (instead
of being skipped).

Thinking further about it: it might be better to make set_uuid return
ENOTSUP for all the unsupported filesystems (including older
btrfs-tools case). This way, the perl snippet above could check, when
set_uuid fails, for the last_errno() and consider that a hard failure
if it was different than ENOTSUP. Something like (untested):

 eval {
     $g->set_uuid (...);
 };
 my $err = $g->last_errno ();
 if ($err == 0) {
     my $uuid = $g->vfs_uuid (...);
     die ...
 } elsif ($err != Errno::ENOTSUP()) {
     die $@
 }

-- 
Pino Toscano