Re: [PATCH 06/13] lightnvm: pblk: Ensure that erase is chunk aligned

[Igor Konopko <igor.j.konopko@intel.com>]

On 05.03.2019 09:20, Hans Holmberg wrote:
> On Mon, Mar 4, 2019 at 2:00 PM Matias Bjørling <mb@lightnvm.io> wrote:
>>
>> On 3/4/19 1:44 PM, Igor Konopko wrote:
>>>
>>>
>>> On 04.03.2019 12:43, Hans Holmberg wrote:
>>>> On Mon, Mar 4, 2019 at 10:11 AM Javier González <javier@javigon.com>
>>>> wrote:
>>>>>
>>>>>> On 4 Mar 2019, at 10.05, Hans Holmberg
>>>>>> <hans.ml.holmberg@owltronix.com> wrote:
>>>>>>
>>>>>> I strongly disagree with adding code that would mask implantation
>>>>>> errors.
>>>>>>
>>>>>> If we want more internal checks, we could add an if statement that
>>>>>> would only be compiled in if CONFIG_NVM_PBLK_DEBUG is enabled.
>>>>>>
>>>>>
>>>>> Not sure who this is for - better not to top post.
>>>>>
>>>>> In any case, this is a spec grey zone. I’m ok with cleaning the bits as
>>>>> they mean nothing for the reset command. If you feel that strongly about
>>>>> this, you can take if with Igor.
>>>>
>>>> Pardon the top-post. It was meant for both you and Igor.
>>>>
>>>
>>> OCSSD 2.0 spec for vector chunk reset (chapter 2.2.2) explicitly says
>>> "The addresses in the LBA list shall be the first logical block address
>>> of each chunk to be reset.". So in my understanding we suppose to clear
>>> the sectors bits of the PPA address in order to be spec compliant.
>>>
>>
>> Agree. And since ppa_addr is allocated on the stack, it should be either
>> memset or the remaining fields should be set to 0. Maybe better to zero
>> initialize in declaration?
> 
> Ah, I thought this was not needed, as ppa is initialized as:
> 
> ppa = pblk->luns[bit].bppa; /* set ch and lun */
> 
> and luns[bit].bppa is initialized to on a value that originally comes
> from drivers/lightnvm/core.c:196
> (and that's explicitly zeroing all 64 bits before setting ch and lun)
> 
> Let me know if i don't make sense here.
> 

I just noticed the same.

In two places (pblk-core:1095 and pblk-map:205) we are using values 
initialized previously in core.c - so my changes are not needed here.

But still there is one place (pblk-map:163) where we initializing 
erase_ppa based on ppa_list[i], which has PPA sector set in most of the 
cases, so this zeroing is still needed here.

>>
>>>>>
>>>>>>
>>>>>> On Mon, Mar 4, 2019 at 8:48 AM Javier González <javier@javigon.com>
>>>>>> wrote:
>>>>>>>> On 27 Feb 2019, at 18.14, Igor Konopko <igor.j.konopko@intel.com>
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>> In current pblk implementation of erase command
>>>>>>>> there is a chance tha sector bits are set to some
>>>>>>>> random values for erase PPA. This is unexpected
>>>>>>>> situation, since erase shall be always chunk
>>>>>>>> aligned. This patch fixes that issue
>>>>>>>>
>>>>>>>> Signed-off-by: Igor Konopko <igor.j.konopko@intel.com>
>>>>>>>> ---
>>>>>>>> drivers/lightnvm/pblk-core.c | 1 +
>>>>>>>> drivers/lightnvm/pblk-map.c  | 2 ++
>>>>>>>> 2 files changed, 3 insertions(+)
>>>>>>>>
>>>>>>>> diff --git a/drivers/lightnvm/pblk-core.c
>>>>>>>> b/drivers/lightnvm/pblk-core.c
>>>>>>>> index a98b2255f963..78b1eea4ab67 100644
>>>>>>>> --- a/drivers/lightnvm/pblk-core.c
>>>>>>>> +++ b/drivers/lightnvm/pblk-core.c
>>>>>>>> @@ -978,6 +978,7 @@ int pblk_line_erase(struct pblk *pblk, struct
>>>>>>>> pblk_line *line)
>>>>>>>>
>>>>>>>>                ppa = pblk->luns[bit].bppa; /* set ch and lun */
>>>>>>>>                ppa.a.blk = line->id;
>>>>>>>> +             ppa.a.reserved = 0;
>>>>>>>>
>>>>>>>>                atomic_dec(&line->left_eblks);
>>>>>>>>                WARN_ON(test_and_set_bit(bit, line->erase_bitmap));
>>>>>>>> diff --git a/drivers/lightnvm/pblk-map.c
>>>>>>>> b/drivers/lightnvm/pblk-map.c
>>>>>>>> index 79df583ea709..aea46b4ec40f 100644
>>>>>>>> --- a/drivers/lightnvm/pblk-map.c
>>>>>>>> +++ b/drivers/lightnvm/pblk-map.c
>>>>>>>> @@ -161,6 +161,7 @@ int pblk_map_erase_rq(struct pblk *pblk,
>>>>>>>> struct nvm_rq *rqd,
>>>>>>>>
>>>>>>>>                        *erase_ppa = ppa_list[i];
>>>>>>>>                        erase_ppa->a.blk = e_line->id;
>>>>>>>> +                     erase_ppa->a.reserved = 0;
>>>>>>>>
>>>>>>>>                        spin_unlock(&e_line->lock);
>>>>>>>>
>>>>>>>> @@ -202,6 +203,7 @@ int pblk_map_erase_rq(struct pblk *pblk,
>>>>>>>> struct nvm_rq *rqd,
>>>>>>>>                atomic_dec(&e_line->left_eblks);
>>>>>>>>                *erase_ppa = pblk->luns[bit].bppa; /* set ch and lun */
>>>>>>>>                erase_ppa->a.blk = e_line->id;
>>>>>>>> +             erase_ppa->a.reserved = 0;
>>>>>>>>        }
>>>>>>>>
>>>>>>>>        return 0;
>>>>>>>> --
>>>>>>>> 2.17.1
>>>>>>>
>>>>>>> I’m fine with adding this, but note that there is actually no
>>>>>>> requirement for the erase to be chunk aligned - the only bits that
>>>>>>> should be looked at are group, PU and chunk.
>>>>>>>
>>>>>>> Reviewed-by: Javier González <javier@javigon.com>
>>