> On 3 Aug 2018, at 14.30, Matias Bjørling <mb@xxxxxxxxxxx> wrote: > > On 08/03/2018 02:02 PM, Javier Gonzalez wrote: >>> On 3 Aug 2018, at 13.57, Matias Bjørling <mb@xxxxxxxxxxx> wrote: >>> >>> On 07/24/2018 09:54 AM, Javier Gonzalez wrote: >>>>> On 29 Jun 2018, at 13.28, Matias Bjørling <mb@xxxxxxxxxxx> wrote: >>>>> >>>>> On 06/29/2018 01:22 PM, Javier Gonzalez wrote: >>>>>>> On 29 Jun 2018, at 13.14, Matias Bjørling <mb@xxxxxxxxxxx> wrote: >>>>>>> >>>>>>> On 06/28/2018 11:12 AM, Javier González wrote: >>>>>>>> The Open-Channel 1.2 spec does not define a mechanism for the host to >>>>>>>> recover the block (chunk) state. As a consequence, a newly format device >>>>>>>> will need to reconstruct the state. Currently, pblk assumes that blocks >>>>>>>> are not erased, which might cause double-erases in case that the device >>>>>>>> does not protect itself against them (which is not specified in the spec >>>>>>>> either). >>>>>>> >>>>>>> It should not be specified in the spec. It is up to the device to handle >>>>>>> double erases and not do it. >>>>>>> >>>>>>>> This patch, reconstructs the state based on read errors. If the first >>>>>>>> sector of a block returns and empty page (NVM_RSP_ERR_EMPTYPAGE), then >>>>>>>> the block s marked free, i.e., erased and ready to be used >>>>>>>> (NVM_CHK_ST_FREE). Otherwise, the block is marked as closed >>>>>>>> (NVM_CHK_ST_CLOSED). Note that even if a block is open and not fully >>>>>>>> written, it has to be erased in order to be used again. >>>>>>> >>>>>>> Should we extend it to do the scan, and update the write pointer as >>>>>>> well? I think this kind of feature already is baked into pblk? >>>>>> This is already in place: we scan until empty page and take it from >>>>>> there. This patch is only for the case in which we start a pblk instance >>>>>> form scratch. On a device already owned by pblk, we would not have the >>>>>> problem we are trying to solve here because we know the state. >>>>> >>>>> Agree. What I meant was that when we anyway are recovering the state, >>>>> we could just as well update ->wp and set to NVM_CHK_ST_OPEN and so >>>>> forth for the initialization phase. >>>> In 1.2 the use of chunk metadata is purely fictional. We respect the >>>> chunk state machine as we transition lines, but all the write pointers >>>> are ignored. Instead, we use the line bitmap to point to the next >>>> writable entry. This is BTW the same way we it in open lines on 2.0 too. >>> >>> Now I understand where you are coming from. I had the understanding >>> that we where using the write pointer now that we moved to 2.0, >>> looking through the code, that wasn't the case. :) Which means that >>> pblk doesn't work with a devices that implements 2.0. Yikes... I knew >>> I had forgot a detail when support was added into pblk. >> I think you misunderstood; pblk does support 2.0 devices. What happens >> is that we transform the per chunk WP in 2.0 into the line bitmap to >> simplify the lookup. The point being that we do not need to create a >> fictional chunk for 1.2 devices since we do the translation to the >> bitmap directly. Does this make sense? > > The chunk->wp isn't used anywhere. So it can't take wp into account. > It uses the EMPTYPAGE marker from 1.2 instead. See pblk-core and > pblk-recovery. > I see that the patches for this are still internal. Will post for 4.20 >>> There are no empty sector marker in the 2.0 spec, since it uses the >>> write pointer to know where it is in the chunk. So there is a bit of >>> work to do there. >> Yes. And for 2.0 devices we go and look at the WP, but for 1.2 devices we >> need to scan. >>> Since this properly is a bit more work to do, I'll look into it after FMS. >> Look the comments above. All we need for 2.0 support is in place. We can >> talk about it f2f. >>> I'm also moving the explicit coding of 1.2/2.0 chunk / bad block >>> fixing into core, so pblk can be simplfied, and doesn't have to think >>> to manage each version separately. >> Good. I have a patch I was expecting to send after FMS for moving chunk >> / bad block out of pblk for the same reason. If you're doing the same >> thing I can stop looking into it... > > I am, will post when done. Cool! Javier
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