Re: new scrub code vs zoned file systems

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

On 2023/6/1 13:21, Naohiro Aota wrote:
> On Thu, Jun 01, 2023 at 02:17:22PM +0900, Naohiro Aota wrote:
>> On Thu, Jun 01, 2023 at 01:00:40PM +0800, Qu Wenruo wrote:
>>>>> But I'm more concerned about why we have a full zone before that crash.
>>>>
>>>> I think this is happening because we can't account for the zone filling
>>>> without the proper context.
>>>
>>> I believe it's a different problem, maybe some de-sync between scrub
>>> write_pointer and the real zoned pointer inside the device.
>>>
>>> My current guess is, the target zone inside the target device is not
>>> properly reset before dev-replace.
>>
>> This must be a different issue. Are we choosing that zone for zone finish
>> to free the active zone resource?
>
> BTW, you may want to use this patch to track zone finishing.

Is there any function that I can go to grab the current writer pointer?

The new trace events only output the flags and used bytes, or the used
bytes is the write pointer already?

Thanks,
Qu

>
> diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
> index dbac203ea54a..5b4ab12368c9 100644
> --- a/fs/btrfs/zoned.c
> +++ b/fs/btrfs/zoned.c
> @@ -2015,6 +2015,7 @@ static int do_zone_finish(struct btrfs_block_group *block_group, bool fully_writ
>   		btrfs_dev_clear_active_zone(device, physical);
>   	}
>
> +	trace_btrfs_zone_finish_block_group(block_group);
>   	if (!fully_written)
>   		btrfs_dec_block_group_ro(block_group);
>
> diff --git a/include/trace/events/btrfs.h b/include/trace/events/btrfs.h
> index 8ea9cea9bfeb..594e4aca0a02 100644
> --- a/include/trace/events/btrfs.h
> +++ b/include/trace/events/btrfs.h
> @@ -2057,6 +2057,12 @@ DEFINE_EVENT(btrfs__block_group, btrfs_skip_unused_block_group,
>   	TP_ARGS(bg_cache)
>   );
>
> +DEFINE_EVENT(btrfs__block_group, btrfs_zone_finish_block_group,
> +	TP_PROTO(const struct btrfs_block_group *bg_cache),
> +
> +	TP_ARGS(bg_cache)
> +);
> +
>   TRACE_EVENT(btrfs_set_extent_bit,
>   	TP_PROTO(const struct extent_io_tree *tree,
>   		 u64 start, u64 len, unsigned set_bits),