Re: Weird behaviour with lsblk and freshly created loop device

[Francis Moreau <francis.moro@gmail.com>]

On 09/02/2014 09:30 AM, Karel Zak wrote:
> On Tue, Sep 02, 2014 at 09:03:45AM +0200, Francis Moreau wrote:
>> It seems that lsblk uses udev to get some block device metadata and asks
>> some others to the kernel. If so, it makes the whole process racy
>> because udev might not have handled the events sent by the kernel yet.
>>
>> I'm not sure why udev is used by default in the first place, what are
> 
>  * info from udev is accessible for non-root users
>  * it's better to scan devices only once on one place only
>  * udev is able to gather information from more sources (for example
>    libblkid does not provide WWN)
> 
>> the benefits ? Using libblkid, at least by default seems the right thing
>> to do.
>>
>> Otherwise maybe lsblk should do the equivalent of 'udevadm settle' to
>> handle correctly freshly created devices ?
> 
> That's question, now (because it's not hardcoded to lsblk) everyone is
> able to control this behavior, all you need is to add 'udevadm settle'
> to your use-case. 

The question is more why let the user do that ?

If lsblk reports the partitions, shouldn't it do that only when it's
sure to fully have retrieve the partition's metadata ?

BTW, is the user supposed to know that lsblk relies on udev or is this
implementation detail ?

Thanks