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

Hans Holmberg
2019-03-05T08:40:55Z

On Tue, Mar 5, 2019 at 9:26 AM Igor Konopko <igor.j.konopko@intel.com> wrote:
>
>
>
> 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.

Yes, you are right, thanks for pointing it out. Are you ok with just
changing this?

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