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To:     Pankaj Raghav <p.raghav@samsung.com>,
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Subject: Re: [PATCH v4 08/13] btrfs:zoned: make sb for npo2 zone devices align
 with sb log offsets
Thread-Topic: [PATCH v4 08/13] btrfs:zoned: make sb for npo2 zone devices
 align with sb log offsets
Thread-Index: AQHYaUWvGG/TZMkJWESbmBi0yiTiyA==
Date:   Tue, 17 May 2022 06:50:53 +0000
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On 16/05/2022 18:55, Pankaj Raghav wrote:=0A=
> Superblocks for zoned devices are fixed as 2 zones at 0, 512GB and 4TB.=
=0A=
> These are fixed at these locations so that recovery tools can reliably=0A=
> retrieve the superblocks even if one of the mirror gets corrupted.=0A=
> =0A=
> power of 2 zone sizes align at these offsets irrespective of their=0A=
> value but non power of 2 zone sizes will not align.=0A=
> =0A=
> To make sure the first zone at mirror 1 and mirror 2 align, write zero=0A=
> operation is performed to move the write pointer of the first zone to=0A=
> the expected offset. This operation is performed only after a zone reset=
=0A=
> of the first zone, i.e., when the second zone that contains the sb is FUL=
L.=0A=
=0A=
Hi Pankaj, stupid question. Npo2 devices still have a zone size being a =0A=
multiple of 4k don't they?=0A=
=0A=
If not, we'd need to also have a tail padding of the superblock zones, in o=
rder=0A=
to move the WP of these zones to the end, so the sb-log states match up.=0A=