From: Damien Le Moal <dlemoal@kernel.org>
To: Johannes Thumshirn <johannes.thumshirn@wdc.com>,
"axboe@kernel.dk" <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org, Naohiro Aota <naohiro.aota@wdc.com>
Subject: Re: [PATCH] block: fix cached zone reports on devices with native zone append
Date: Tue, 9 Dec 2025 20:33:37 -0800 [thread overview]
Message-ID: <5f521c8d-5c26-4a4a-96a5-034906d7792f@kernel.org> (raw)
In-Reply-To: <20251210021037.10106-1-johannes.thumshirn@wdc.com>
On 2025/12/09 18:10, Johannes Thumshirn wrote:
> When mounting a btrfs file system on virtio-blk which supports native
> Zone Append there has been a WARN triggering in btrfs' space management
> code.
>
> Further looking into btrfs' zoned statistics uncovered the filesystem
> expecting the zones to be used, but the write pointers being 0:
> # cat /sys/fs/btrfs/8eabd2e7-3294-4f9e-9b58-7e64135c8bf4/zoned_stats
> active block-groups: 4
> reclaimable: 0
> unused: 0
> need reclaim: false
> data relocation block-group: 1342177280
> active zones:
> start: 1073741824, wp: 0 used: 0, reserved: 0, unusable: 0
> start: 1342177280, wp: 0 used: 0, reserved: 0, unusable: 0
> start: 1610612736, wp: 0 used: 16384, reserved: 0, unusable: 18446744073709535232
> start: 1879048192, wp: 0 used: 131072, reserved: 0, unusable: 18446744073709420544
>
> Looking at the blkzone report output for the zone in question
> (1610612736) the write pointer on the device moved, but the filesystem
> did not see a change on the write pointer:
> # blkzone report -c 1 -o 0x300000 /dev/vda
> start: 0x000300000, len 0x080000, cap 0x080000, wptr 0x000040 reset:0 non-seq:0, zcond: 2(oi) [type: 2(SEQ_WRITE_REQUIRED)]
>
> The zone write pointer is 0, because btrfs is using the cached version
> of blkdev_report_zones() and as virtio-blk is supporting native zone
> append, but blkdev_revalidate_zones() does not initialize the zone write
> plugs in this case.
>
> Not skipping the revalidate of sequential zones in
> blkdev_revalidate_zones() callchain fixes this issue.
May be here, add: Adding zone write plugs for active zones is not an issue
because these plugs will be removed if the user issues a zone append command and
this same operation will also disable the cached report zones.
>
> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Maybe also add a fixes tag for completeness ?
Other than that, looks OK to me.
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
--
Damien Le Moal
Western Digital Research
next prev parent reply other threads:[~2025-12-10 4:33 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-10 2:10 [PATCH] block: fix cached zone reports on devices with native zone append Johannes Thumshirn
2025-12-10 4:33 ` Damien Le Moal [this message]
2025-12-10 5:27 ` Christoph Hellwig
2025-12-10 5:37 ` Jens Axboe
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