zloop: truncate finished zones to zone capacity

commit 72e67c118642634c25465db0c8bcfa54c4ce086c upstream.

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: eb0570c7df23 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 6 insertions, 6 deletions

diff --git a/Documentation/admin-guide/blockdev/zoned_loop.rst b/Documentation/admin-guide/blockdev/zoned_loop.rst
index f4f1f3121bf9..95974425ca05 100644
--- a/Documentation/admin-guide/blockdev/zoned_loop.rst
+++ b/Documentation/admin-guide/blockdev/zoned_loop.rst
@@ -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,
diff --git a/drivers/block/zloop.c b/drivers/block/zloop.c
index 55eeb6aac0ea..1333fae05ac5 100644
--- a/drivers/block/zloop.c
+++ b/drivers/block/zloop.c
@@ -478,7 +478,8 @@ 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;