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zloop: truncate finished zones to zone capacity

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The size of a sequential zone backing file records the amount of data
written and is used to restore the zone state. A backing file whose size
is equal to the zone capacity is restored as a full zone, while a file
larger than the zone capacity is rejected as invalid.

However, zloop_finish_zone() currently truncates the backing file to the
zone size. For devices with a reduced zone capacity, finishing a zone
therefore creates a backing file larger than the zone capacity. After the
device is removed and later re-added, that zone file is rejected instead
of being restored as a full zone.

Truncate finished sequential zones to the zone capacity, matching the
persistent representation accepted by zloop_update_seq_zone() for a full
zone.

Suggested-by: Damien Le Moal <dlemoal@kernel.org>
Fixes: eb0570c7df ("block: new zoned loop block device driver")
Cc: stable@vger.kernel.org
Signed-off-by: Xu Rao <raoxu@uniontech.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://patch.msgid.link/B39E5FD81D1A07F4+20260804023403.939767-1-raoxu@uniontech.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Xu Rao 2026-08-04 10:34:03 +08:00 committed by Jens Axboe
parent d507d3cb19
commit 72e67c1186
2 changed files with 6 additions and 6 deletions
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9
Documentation/admin-guide/blockdev/zoned_loop.rst
View File

@ -30,11 +30,10 @@ indicates the position of the write pointer of the zone.
When resetting a sequential zone, its backing file size is truncated to zero.
Conversely, for a zone finish operation, the backing file is truncated to the
zone size. With this, the maximum capacity of a zloop zoned block device created
can be larger configured to be larger than the storage space available on the
backing file system. Of course, for such configuration, writing more data than
the storage space available on the backing file system will result in write
errors.
zone capacity. With this, a zloop zoned block device can be configured with a
larger capacity than the storage space available on the backing file system. Of
course, for such configuration, writing more data than the storage space
available on the backing file system will result in write errors.
The zoned loop block device driver implements a complete zone transition state
machine. That is, zones can be empty, implicitly opened, explicitly opened,

3
drivers/block/zloop.c
View File

@ -479,7 +479,8 @@ static int zloop_finish_zone(struct zloop_device *zlo, unsigned int zone_no)
zone->cond == BLK_ZONE_COND_FULL)
goto unlock;
if (vfs_truncate(&zone->file->f_path, zlo->zone_size << SECTOR_SHIFT)) {
if (vfs_truncate(&zone->file->f_path,
zlo->zone_capacity << SECTOR_SHIFT)) {
set_bit(ZLOOP_ZONE_SEQ_ERROR, &zone->flags);
ret = -EIO;
goto unlock;