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

[Thomas Lamprecht <t.lamprecht@proxmox.com>]

On 24.06.21 09:56, Fabian Grünbichler wrote:
> 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..
> 

But then we create already the sub-directories in DirPlugin's SUPER->activate_storage call
to the base plugin one and leave that stuff over when the assert fails?