> On 3 Aug 2018, at 14.46, Matias Bjørling <mb@xxxxxxxxxxx> wrote: > > On 08/03/2018 02:37 PM, Javier Gonzalez wrote: >>> 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 > > Thanks. Please also put a Fixes: on, so it gets backported appropriately. Sure. I will.
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