linux-kernel - Re: [PATCH] lightnvm: pblk: remove unnecessary drive version check

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Message-ID: <E3EFEEB3-8B6A-4743-B383-B29482081CC7@cnexlabs.com>
Date:   Fri, 3 Aug 2018 13:05:08 +0000
From:   Javier Gonzalez <javier@...xlabs.com>
To:     Matias Bjørling <mb@...htnvm.io>
CC:     "Konopko, Igor J" <igor.j.konopko@...el.com>,
        "marcin.dziegielewski@...el.com" <marcin.dziegielewski@...el.com>,
        Hans Holmberg <hans.holmberg@...xlabs.com>,
        Heiner Litz <hlitz@...c.edu>,
        Young Tack Tack Jin <youngtack.jin@...cuitblvd.com>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] lightnvm: pblk: remove unnecessary drive version check


> On 3 Aug 2018, at 14.55, Matias Bjørling <mb@...htnvm.io> wrote:
> 
> On 08/03/2018 02:39 PM, Matias Bjørling wrote:
>> On 08/03/2018 02:18 PM, Javier Gonzalez wrote:
>>>> On 2 Aug 2018, at 22.58, Matias Bjørling <mb@...htnvm.io> wrote:
>>>> 
>>>> The nvme driver checks for 1.2 and 2.0 compatibility. If an unsupported
>>>> version is reported, the device will not be initialized.
>>>> 
>>>> Signed-off-by: Matias Bjørling <mb@...htnvm.io>
>>>> ---
>>>> drivers/lightnvm/pblk-init.c | 8 --------
>>>> 1 file changed, 8 deletions(-)
>>>> 
>>>> diff --git a/drivers/lightnvm/pblk-init.c b/drivers/lightnvm/pblk-init.c
>>>> index 537e98f2b24a..e9e2fedff387 100644
>>>> --- a/drivers/lightnvm/pblk-init.c
>>>> +++ b/drivers/lightnvm/pblk-init.c
>>>> @@ -1202,14 +1202,6 @@ static void *pblk_init(struct nvm_tgt_dev *dev, struct gendisk *tdisk,
>>>>     pblk->state = PBLK_STATE_RUNNING;
>>>>     pblk->gc.gc_enabled = 0;
>>>> 
>>>> -    if (!(geo->version == NVM_OCSSD_SPEC_12 ||
>>>> -                    geo->version == NVM_OCSSD_SPEC_20)) {
>>>> -        pblk_err(pblk, "OCSSD version not supported (%u)\n",
>>>> -                            geo->version);
>>>> -        kfree(pblk);
>>>> -        return ERR_PTR(-EINVAL);
>>>> -    }
>>>> -
>>>>     if (geo->version == NVM_OCSSD_SPEC_12 && geo->dom & NVM_RSP_L2P) {
>>>>         pblk_err(pblk, "host-side L2P table not supported. (%x)\n",
>>>>                             geo->dom);
>>>> --
>>>> 2.11.0
>>> 
>>> The same comment goes for this patch. pblk does support 2.0 and 1.2
>>> today, but it is not guaranteed it will support a new revision straight
>>> away. So I think that a check wither here or through the .capabilities I
>>> proposed on the other patch is necessary.
>> Works for me. I'll send another patch that enables pblk target to tell which version it supports.
> 
> On second thought. The idea is that pblk will not have to think about
> 1.2/2.0. The core will expose a general address format, etc., such
> that pblk doesn't have to be complicated by that.
> 

Yes! This was the main motivation for me starting looking into moving
things down.

An issue you might hit is that some conversions are very tightly couple
with pblk (e.g., 32/64 bit L2P conversions). In the code I have on my
end, I ended up having helpers for it, but it does not feel right.

i'm happy to share some thoughts if you want...

> I am working on the various pieces and moving them to core. The patch
> may have gone out a bit early. I will send this again when the 1.2/2.0
> conversions have been applied.

Cool.

Thanks!
Javier



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