linux-kernel - Re: [PATCH v2 2/2] lightnvm: add non-continuous lun target creation support

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Date:	Thu, 28 Jan 2016 18:19:49 +0800
From:	Wenwei Tao <ww.tao0320@...il.com>
To:	Matias Bjørling <mb@...htnvm.io>
Cc:	linux-kernel@...r.kernel.org, linux-block@...r.kernel.org
Subject: Re: [PATCH v2 2/2] lightnvm: add non-continuous lun target creation support

OK, I see. Will include these changes in next version.

2016-01-28 17:09 GMT+08:00 Matias Bjørling <mb@...htnvm.io>:
> On 01/28/2016 09:50 AM, Wenwei Tao wrote:
>> 2016-01-27 17:44 GMT+08:00 Matias Bjørling <mb@...htnvm.io>:
>>> On 01/26/2016 01:33 PM, Wenwei Tao wrote:
>>>> When create a target, we specify the begin lunid and
>>>> the end lunid, and get the corresponding continuous
>>>> luns from media manager, if one of the luns is not free,
>>>> we failed to create the target, even if the device's
>>>> total free luns are enough.
>>>>
>>>> So add non-continuous lun target creation support,
>>>> thus we can improve the backend device's space utilization.
>>>> Signed-off-by: Wenwei Tao <ww.tao0320@...il.com>
>>>> ---
>>>> Changes since v1:
>>>> -use NVM_FIXED instead NVM_C_FIXED in gennvm_get_lun
>>>> -add target creation flags check
>>>> -rebase to v4.5-rc1
>>>>
>>>>  drivers/lightnvm/core.c       |  36 ++++---
>>>>  drivers/lightnvm/gennvm.c     |  42 ++++++++-
>>>>  drivers/lightnvm/rrpc.c       | 215 +++++++++++++++++++++++++++---------------
>>>>  drivers/lightnvm/rrpc.h       |   6 +-
>>>>  include/linux/lightnvm.h      |  24 ++++-
>>>>  include/uapi/linux/lightnvm.h |   3 +
>>>>  6 files changed, 229 insertions(+), 97 deletions(-)
>>>>
>>>
>>> Hi Wenwei,
>>>
>>> I did some digging on the patch and changed the interface to a
>>> reserve/release interface. I also removed the logic to dynamically
>>> select another lun than the one requested.
>>>
>>> A couple of questions:
>>>
>>>  1. The rrpc_lun->rev_lock and rev_trans_map change; this might be for
>>> another patch, and it isn't directly related to continuous mapping?
>>
>> rrpc_lun->rev_lock and rev_trans_map change is related to
>> non-continuous mapping, it's not directly related to continuous
>> mapping.
>> Put this change in  another patch along with non-continuous mapping
>> support and this patch would be only add reserve/release thing, is
>> that your suggestion?
>
> Yes, that would be great. Then we keep it separate. I'll like to do some
> benchmarks with the patch on and off, to see the performance difference.
>
>>
>>>  2. Instead of dynamically assigning new luns when not available, what
>>> about taking a list of lun ids instead?
>>>
>>
>> Seems you prefer user make the choice ?
>
> Yes, I want it to be deterministic. For example, if we do it
> dynamically, the user might first allocate 2-4, and then allocate 1-3 ,
> which will actually allocate 0,1,5. Then later, a user tries to allocate
> on 0, and instead gets returned 6. It quickly makes it difficult to use.
>
>> But the target creation can still fail if one of the list lun ids is
>> not available although there may be enough free luns.
>
> Agree, the user would have to look up the free luns and then resubmit
> the target allocation.