kernel/linux.git/drivers/block/zloop.c, branch v6.18.21

zloop: check for spurious options passed to remove

2026-03-12T11:09:16+00:00

[ Upstream commit 3c4617117a2b7682cf037be5e5533e379707f050 ] Zloop uses a command option parser for all control commands, but most options are only valid for adding a new device. Check for incorrectly specified options in the remove handler. Fixes: eb0570c7df23 ("block: new zoned loop block device driver") Signed-off-by: Christoph Hellwig Reviewed-by: Damien Le Moal Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin

zloop: advertise a volatile write cache

2026-03-12T11:09:16+00:00

[ Upstream commit 6acf7860dcc79ed045cc9e6a79c8a8bb6959dba7 ] Zloop is file system backed and thus needs to sync the underlying file system to persist data. Set BLK_FEAT_WRITE_CACHE so that the block layer actually send flush commands, and fix the flush implementation as sync_filesystem requires s_umount to be held and the code currently misses that. Fixes: eb0570c7df23 ("block: new zoned loop block device driver") Signed-off-by: Christoph Hellwig Reviewed-by: Damien Le Moal Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin

zloop: make the write pointer of full zones invalid

2026-01-02T11:57:28+00:00

commit 866d65745b635927c3d1343ab67e6fd4a99d116d upstream. The write pointer of zones that are in the full condition is always invalid. Reflect that fact by setting the write pointer of full zones to ULLONG_MAX. Fixes: eb0570c7df23 ("block: new zoned loop block device driver") Cc: stable@vger.kernel.org Signed-off-by: Damien Le Moal Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman

zloop: fail zone append operations that are targeting full zones

2026-01-02T11:57:28+00:00

commit cf28f6f923cb1dd2765b5c3d7697bb4dcf2096a0 upstream. zloop_rw() will fail any regular write operation that targets a full sequential zone. The check for this is indirect and achieved by checking the write pointer alignment of the write operation. But this check is ineffective for zone append operations since these are alwasy automatically directed at a zone write pointer. Prevent zone append operations from being executed in a full zone with an explicit check of the zone condition. Fixes: eb0570c7df23 ("block: new zoned loop block device driver") Cc: stable@vger.kernel.org Signed-off-by: Damien Le Moal Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman

zloop: fix KASAN use-after-free of tag set

2025-07-31T21:01:07+00:00

When a zoned loop device, or zloop device, is removed, KASAN enabled kernel reports "BUG KASAN use-after-free" in blk_mq_free_tag_set(). The BUG happens because zloop_ctl_remove() calls put_disk(), which invokes zloop_free_disk(). The zloop_free_disk() frees the memory allocated for the zlo pointer. However, after the memory is freed, zloop_ctl_remove() calls blk_mq_free_tag_set(&zlo->tag_set), which accesses the freed zlo. Hence the KASAN use-after-free. zloop_ctl_remove() put_disk(zlo->disk) put_device() kobject_put() ... zloop_free_disk() kvfree(zlo) blk_mq_free_tag_set(&zlo->tag_set) To avoid the BUG, move the call to blk_mq_free_tag_set(&zlo->tag_set) from zloop_ctl_remove() into zloop_free_disk(). This ensures that the tag_set is freed before the call to kvfree(zlo). Fixes: eb0570c7df23 ("block: new zoned loop block device driver") CC: stable@vger.kernel.org Signed-off-by: Shin'ichiro Kawasaki Reviewed-by: Christoph Hellwig Link: https://lore.kernel.org/r/20250731110745.165751-1-shinichiro.kawasaki@wdc.com Signed-off-by: Jens Axboe

block: new zoned loop block device driver

2025-05-01T23:03:56+00:00

The zoned loop block device driver allows a user to create emulated zoned block devices using one regular file per zone as backing storage. Compared to null_blk or scsi_debug, it has the advantage of allowing emulating large zoned devices without requiring the same amount of memory as the capacity of the emulated device. Furthermore, zoned devices emulated with this driver can be re-started after a host reboot without any loss of the state of the device zones, which is something that null_blk and scsi_debug do not support. This initial implementation is simple and does not support zone resource limits. That is, a zoned loop block device limits for the maximum number of open zones and maximum number of active zones is always 0. This driver can be either compiled in-kernel or as a module, named "zloop". Compilation of this driver depends on the block layer support for zoned block device (CONFIG_BLK_DEV_ZONED must be set). Using the zloop driver to create and delete zoned block devices is done by writing commands to the zoned loop control character device file (/dev/zloop-control). Creating a device is done with: $ echo "add [options]" > /dev/zloop-control The options available for the "add" operation cat be listed by reading the zloop-control device file: $ cat /dev/zloop-control add id=%d,capacity_mb=%u,zone_size_mb=%u,zone_capacity_mb=%u,conv_zones=%u,base_dir=%s,nr_queues=%u,queue_depth=%u remove id=%d The options available allow controlling the zoned device total capacity, zone size, zone capactity of sequential zones, total number of conventional zones, base directory for the zones backing file, number of I/O queues and the maximum queue depth of I/O queues. Deleting a device is done using the "remove" command: $ echo "remove id=0" > /dev/zloop-control This implementation passes various tests using zonefs and fio (t/zbd tests) and provides a state machine for zone conditions that is compliant with the T10 ZBC and NVMe ZNS specifications. Co-developed-by: Christoph Hellwig Signed-off-by: Damien Le Moal Reviewed-by: Johannes Thumshirn Link: https://lore.kernel.org/r/20250407075222.170336-2-dlemoal@kernel.org Signed-off-by: Jens Axboe