Re: [pve-devel] [PATCH storage] btrfs: check for btrfs in on_add_hook and activate

["Fabian Grünbichler" <f.gruenbichler@proxmox.com>]

On June 24, 2021 9:29 am, Wolfgang Bumiller wrote:
> Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
> ---
>  PVE/Storage/BTRFSPlugin.pm | 30 ++++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
> 
> diff --git a/PVE/Storage/BTRFSPlugin.pm b/PVE/Storage/BTRFSPlugin.pm
> index 133edc6..0e111a0 100644
> --- a/PVE/Storage/BTRFSPlugin.pm
> +++ b/PVE/Storage/BTRFSPlugin.pm
> @@ -20,6 +20,7 @@ use constant {
>      FS_NOCOW_FL => 0x00800000,
>      FS_IOC_GETFLAGS => 0x40086602,
>      FS_IOC_SETFLAGS => 0x80086601,
> +    BTRFS_MAGIC => 0x9123683e,
>  };
>  
>  # Configuration (similar to DirPlugin)
> @@ -89,8 +90,29 @@ sub check_config {
>      return PVE::Storage::DirPlugin::check_config($self, $sectionId, $config, $create, $skipSchemaCheck);
>  }
>  
> +my sub getfsmagic($) {
> +    my ($path) = @_;
> +    # The field type sizes in `struct statfs` are defined in a rather annoying way, and we only
> +    # need the first field, which is a `long` for our supported platforms.
> +    # Should be moved to pve-rs, so this can be the problem of the `libc` crate ;-)
> +    # Just round up and extract what we need:
> +    my $buf = pack('x160');
> +    if (0 != syscall(&PVE::Syscall::SYS_statfs, $path, $buf)) {
> +	die "statfs on '$path' failed - $!\n";
> +    }
> +
> +    return unpack('L!', $buf);
> +}
> +
> +my sub assert_btrfs($) {
> +    my ($path) = @_;
> +    die "'$path' is not a btrfs file system\n"
> +	if getfsmagic($path) != BTRFS_MAGIC;
> +}
> +
>  sub activate_storage {
>      my ($class, $storeid, $scfg, $cache) = @_;
> +    assert_btrfs($scfg->{path});
>      return PVE::Storage::DirPlugin::activate_storage($class, $storeid, $scfg, $cache);

shouldn't this be the other way round? first check for things like 
is_mountpoint, then whether btrfs is there.. makes for less confusing 
error message at least..

>  }
>  
> @@ -179,6 +201,14 @@ sub btrfs_cmd {
>      return $msg;
>  }
>  
> +sub on_add_hook {
> +    my ($class, $storeid, $scfg, %param) = @_;
> +
> +    assert_btrfs($scfg->{path});

not needed - adding a new storage calls activate_storage if the storage 
is enabled..

> +
> +    return;
> +}
> +
>  sub btrfs_get_subvol_id {
>      my ($class, $path) = @_;
>      my $info = $class->btrfs_cmd(['subvolume', 'show', '--', $path]);
> -- 
> 2.30.2
> 
> 
> 
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