Re: [patch] reiser4: port for Linux-4.1

[Edward Shishkin <edward.shishkin@gmail.com>]

On 07/05/2015 09:08 PM, Ivan Shapovalov wrote:
> On 2015-07-05 at 02:33 +0800, Edward Shishkin wrote:
>> On 07/05/2015 01:53 AM, Ivan Shapovalov wrote:
>>> On 2015-07-04 at 15:53 +0800, Edward Shishkin wrote:
>>>> [...]
>>>> And how to test directly at mount time?
>>> Something along the lines of
>>> - allocate 1 MiB of contiguous space
>>> - fill it with non-zeros
>>> - for N = 1, 2, 4, ...:
>>>     - discard N sectors from the contiguous space
>>>     - check if anything in the discarded space became zero-filled
>>>     - if it did, infer alignnment from the first zero-filled block,
>>>       infer granularity from the zero-filled region size.
>>
>> mkfs seems to be more suitable for this funny business
> Yeah, sure. So... new superblock format with two extra fields?


The change will be forward and backward compatible, so there is no
need in a new format. Just add two new fields to the superblock40.

Also people will want to "mount -o discard" when discard parameters
are not known. In this case I think to provide them discard_extents().
which is currently merged. Otherwise use discard_precise_extents().

Thanks,
Edward.


>
>>
>>>> It seems that nobody cares about it..
>>> It's just ATA interface does not provide necessary data.
>>
>> OK, so our precise discard extension is waiting for the
>> best times..
> I hope we'll be able to merge it eventually (esp. the final patch which
> accounts for non-idempotence of check-and-allocate-blocks).
>
> Thanks,