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

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Message-ID: <110deaa7-9682-4ddb-a5b0-2b5f627f6044@wdc.com>
Date:   Wed, 13 Sep 2023 14:57:50 +0000
From:   Johannes Thumshirn <Johannes.Thumshirn@....com>
To:     "dsterba@...e.cz" <dsterba@...e.cz>
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 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.