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block: fix cached zone reports on devices with native zone append 

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.

Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Fixes: a6aa36e957 ("block: Remove zone write plugs when handling native zone append writes")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
master
Johannes Thumshirn 2025-12-10 03:10:37 +01:00 committed by Jens Axboe
parent 59e25ef2b4
commit 2c38ec934d
1 changed files with 1 additions and 1 deletions
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2
block/blk-zoned.c
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@ -2100,7 +2100,7 @@ static int blk_revalidate_seq_zone(struct blk_zone *zone, unsigned int idx,
* we have a zone write plug for such zone if the device has a zone
* write plug hash table.
*/
if (!queue_emulates_zone_append(disk->queue) || !disk->zone_wplugs_hash)
if (!disk->zone_wplugs_hash)
return 0;
wp_offset = disk_zone_wplug_sync_wp_offset(disk, zone);