linux-kernel - Re: [PATCH v8 01/11] btrfs: add raid stripe tree definitions

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Date:   Wed, 13 Sep 2023 18:06:51 +0200
From:   David Sterba <dsterba@...e.cz>
To:     Johannes Thumshirn <Johannes.Thumshirn@....com>
Cc:     Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>,
        David Sterba <dsterba@...e.com>,
        Christoph Hellwig <hch@....de>,
        Naohiro Aota <Naohiro.Aota@....com>, Qu Wenruo <wqu@...e.com>,
        Damien Le Moal <dlemoal@...nel.org>,
        "linux-btrfs@...r.kernel.org" <linux-btrfs@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v8 01/11] btrfs: add raid stripe tree definitions

On Wed, Sep 13, 2023 at 02:57:50PM +0000, Johannes Thumshirn wrote:
> On 13.09.23 16:50, David Sterba wrote:
> > On Wed, Sep 13, 2023 at 06:02:09AM +0000, Johannes Thumshirn wrote:
> >> On 12.09.23 22:32, David Sterba wrote:
> >>>> @@ -306,6 +306,16 @@ BTRFS_SETGET_FUNCS(timespec_nsec, struct btrfs_timespec, nsec, 32);
> >>>>    BTRFS_SETGET_STACK_FUNCS(stack_timespec_sec, struct btrfs_timespec, sec, 64);
> >>>>    BTRFS_SETGET_STACK_FUNCS(stack_timespec_nsec, struct btrfs_timespec, nsec, 32);
> >>>>    
> >>>> +BTRFS_SETGET_FUNCS(stripe_extent_encoding, struct btrfs_stripe_extent, encoding, 8);
> >>>
> >>> What is encoding referring to?
> >>
> >> At the moment (only) the RAID type. But in the future it can be expanded
> >> to all kinds of encodings, like Reed-Solomon, Butterfly-Codes, etc...
> > 
> > I see, could it be better called ECC? Like stripe_extent_ecc, that would
> > be clear that it's for the correction, encoding sounds is too generic.
> 
> Hmm but for RAID0 there is no correction, so not really as well. I'd 
> suggest 'type', but I /think/ for RAID5/6 we'll need type=data and 
> type=parity (and future ECC as well).
> 
> Maybe level, as in RAID level? I know currently it is redundant, as we 
> can derive it from the block-group.

Ok, let's keep encoding, we might actually need the genric meaning, what
I was missing was the context.