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

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

On 07/05/2015 11:13 PM, Ivan Shapovalov wrote:
> On 2015-07-05 at 16:06 +0200, Dušan Čolić wrote:
>> On 5 Jul 2015 15:12, "Ivan Shapovalov"<intelfx100@gmail.com>  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?
>>>
>> But what happens when someone makes an image of whole partition and
>> uses it
>> on new different ssd?
> Maybe we can make a tunefs.reiser4 (just) for that purpose.


tunefs utilities usually accept already existing file system as one of 
input arguments.
And it can happen that file system doesn't have enough space for 
"probing". So the
cleanest option would be to create a simple tool for probing an empty 
non-formatted
partition, and supply a script, which:

1) probes an empty partition;
2) dd;
3) updates superblock of the newly created image (by tunefs, etc) with 
proper discard
parameters.

Thanks,
Edward.
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