Re: new scrub code vs zoned file systems

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

On 2023/6/1 12:53, Christoph Hellwig wrote:
> On Thu, Jun 01, 2023 at 06:25:59AM +0800, Qu Wenruo wrote:
>> To me, the problem can be solved in a much simpler way, if it's
>> dev-replace for zoned device, let's write the whole stripe to the target
>> device, and wait for it.
>>
>> For the btrfs_record_physical_zoned(), we can skip the OE things if
>> bbio::inode is NULL.
>>
>> Would the following change solves the problem?
>
> It can't, as we need to record the actually written location.

We don't need, it's scrub, the target block group is marked RO, and we
won't duplicate writes for zoned devices (the FLAG_TO_COPY thing), thus
only scrub can write into the zone.

Furthermore, in the context of scrub, we have always do write and wait
(QD=1, just like metadata writes), and fill the gaps using
fill_writer_pointer_gap() when needed.

In fact, if there is something so basically wrong, we should have all
the replace tests before that b/169 failed.

Thanks,
Qu