mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2025-12-27 15:51:30 -05:00
eb0570c7df
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 <hch@lst.de> Signed-off-by: Damien Le Moal <dlemoal@kernel.org> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Link: https://lore.kernel.org/r/20250407075222.170336-2-dlemoal@kernel.org Signed-off-by: Jens Axboe <axboe@kernel.dk>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.