linux-kernel - Re: [V2 PATCH 0/2] lightnvm: pblk: retrieve chunk metadata on erase

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Date:   Sat, 6 Oct 2018 03:13:17 +0200
From:   Matias Bjørling <mb@...htnvm.io>
To:     javier@...igon.com
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        javier@...xlabs.com
Subject: Re: [V2 PATCH 0/2] lightnvm: pblk: retrieve chunk metadata on erase

On 10/04/2018 09:13 AM, Javier González wrote:
> Changes singe V1:
>    - remove sanity checks on the fast path
> 
> This patchset implements support for retrieving chunk metadata on reset.
> This is the base for implementing wear-leveling and allowing chunks to
> shrink at runtime.
> 
> Javier
> 
> Javier González (2):
>    lightnvm: pblk: add helper for printing chunk state
>    lightnvm: pblk: retrieve chunk metadata on erase
> 
>   drivers/lightnvm/core.c      | 44 ++++++++++++++++++++++++++++++++++--
>   drivers/lightnvm/pblk-core.c | 54 +++++++++++++++++++++++++++++++++-----------
>   drivers/lightnvm/pblk.h      |  9 ++++++++
>   3 files changed, 92 insertions(+), 15 deletions(-)
> 

Right now there isn't a way in the spec to tell if the drive supports 
this feature or not, and DSM Reset doesn't support it either. Making it 
a bug in the spec. Until the updated spec is out, I like to avoid adding 
this feature into the kernel.

The Get Log Page approach can be used for wear-levelling information. 
Similarly for knowing when a chunk shrink, pblk can't rely on a chunk 
not shrinking at runtime (and reporting early close error), so in the 
case this happens, pblk can either continue business as usual, or resync 
with the drive.