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

Hans Holmberg
2019-03-05T08:21:10Z

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.

>
> >>>
> >>>>
> >>>> 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>
>