Re: [PATCH v2] loop: add some basic read-only sysfs attributes

[Jens Axboe <axboe@kernel.dk>]

On 2010-08-23 14:29, Karel Zak wrote:
> On Fri, Jul 30, 2010 at 04:34:43PM +0200, Kay Sievers wrote:
>> On Fri, Jul 30, 2010 at 16:22, Milan Broz <mbroz@redhat.com> wrote:
>>> On 07/30/2010 06:36 AM, Kay Sievers wrote:
>>>
>>>> Alternatively, these attributes could be created and removed/created
>>>> with the ioctl, and before the 'change' event, only if there is an
>>>> active backing file, but I would expect the attribute group at the
>>>> device to work just fine.
>>> I have no idea how you can add attribute group before add_disk() which
>>> initializes kobj (it ends with BUG_ON in internal_create_group
>>> - because !kobj->sd). Perhaps I missed something?
>>
>> Attribute groups handle the creation of a kobject (subdir) for you,
>> you only supply a name to the group. Without a name, they will put all
>> the attributes in the root of the device.
>>
>> The 'struct device' has a member **groups, and that can have a list of
>> attribute groups assigned. You assign them before you register the
>> device, and the core will take care of everything.
>>
>>> Anyway, second approach works - now is loop attributes available only
>>> when loop is configured and before CHANGE uevent is sent.
>>>
>>> Ok with that?
>>
>> Sounds good, nothing to complain from a sysfs timing perspective.
> 
> Jens, ping... it would be really really nice to have this feature in 
> kernel. 
> 
> The ioctls are useless and I'd like to minimize number of situations
> where mount(8) behaviour depends on /etc/mtab.

Looks good to me as well and agree on the ioctls. Care to resend
a fresh patch and I will queue it up for 2.6.37.

-- 
Jens Axboe