Re: /sys/block and /dev and partitions

[Loic Dachary <loic@dachary.org>]

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On 18/08/2015 11:53, Ilya Dryomov wrote:
> On Tue, Aug 18, 2015 at 12:46 AM, Loic Dachary <loic@dachary.org> wrote:
>> Hi Ilya,
>>
>> For regular devices such as /dev/vdb2 or /dev/sda3, do you think it is safe to use /sys/dev/block/M:m/partition to figure out the partition number ? Or could it vary depending on the disk driver or the partition table layout ? Or the kernel version ?
> 
> Yes, I think it is.  "partition" was added specifically for finding out
> partition numbers after extended devt scheme was merged, because it
> made it impossible to use arithmetic on minor numbers.  That happened
> around 2.6.27 - 2.6.28, so it's a more recent one compared to others,
> but I don't think you care about anything pre 2.6.32.
> 
> (You could choose not to rely on "partition" and access() "start" for
> figuring out if the thing is a partition - it's been around forever,
> but then, the only way to figure out the partition index would be to
> parse the name, which you want to avoid.)

Exactly. Really happy to get rid of the name parsing logic :-)

> Thanks,
> 
>                 Ilya
> 

-- 
Loïc Dachary, Artisan Logiciel Libre


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