linux-kernel - Re: [PATCH v2 5/6] lightnvm: remove nvm_dev_ops->max_phys

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Message-ID: <CE52AA06-A417-4BD6-BCED-EB4035FC6906@cnexlabs.com>
Date:   Mon, 19 Feb 2018 11:05:17 +0000
From:   Javier Gonzalez <javier@...xlabs.com>
To:     Matias Bjørling <mb@...htnvm.io>
CC:     "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>
Subject: Re: [PATCH v2 5/6] lightnvm: remove nvm_dev_ops->max_phys_sect

> On 19 Feb 2018, at 08.31, Matias Bjørling <mb@...htnvm.io> wrote:
> 
> On 02/16/2018 07:48 AM, Javier Gonzalez wrote:
>>> On 15 Feb 2018, at 05.11, Matias Bjørling <mb@...htnvm.io> wrote:
>>> 
>>> The value of max_phys_sect is always static. Instead of
>>> defining it in the nvm_dev_ops structure, declare it as a global
>>> value.
>>> 
>>> Signed-off-by: Matias Bjørling <mb@...htnvm.io>
>>> ---
>>> drivers/lightnvm/core.c          | 28 +++++++---------------------
>>> drivers/lightnvm/pblk-init.c     |  9 ++++-----
>>> drivers/lightnvm/pblk-recovery.c |  8 ++------
>>> drivers/nvme/host/lightnvm.c     |  5 +----
>>> include/linux/lightnvm.h         |  5 ++---
>>> 5 files changed, 16 insertions(+), 39 deletions(-)
>> The patch looks good, but I have a question. If a target implements the
>> scalar interface, then it will not be limited to 64 lbas/ppas and it
>> will not make sense to split the bio base don this value. In fact, it
>> looks like in time, we will move to a scalar interface in the 2.0 path
>> to align with the zoned interface, so this value will be dependent on
>> whether the target is using the scalar or vector interface.
> 
> Both read/write and vector interface will coexist. I am only removing
> what is hardwired into the specification.
> 
> The read/write interface has always been able issue more than 64 LBAs,
> it is instead limited by what the hardware reports its max transfer
> size to be.
> 

Exactly. I was thinking of a similar mechanism for the vector interface
to simplify integration with the scalar interface and avoid having an
if/else for what we now call max_phys_sect.

I guess we can wait and see what the code looks like when we adapt pblk.

Reviewed-by: Javier González <javier@...xlabs.com>

Javier

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