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path: root/drivers/md/dm-zoned.h
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2019-11-07dm zoned: reduce overhead of backing device checksDmitry Fomichev1-0/+2
Commit 75d66ffb48efb3 added backing device health checks and as a part of these checks, check_events() block ops template call is invoked in dm-zoned mapping path as well as in reclaim and flush path. Calling check_events() with ATA or SCSI backing devices introduces a blocking scsi_test_unit_ready() call being made in sd_check_events(). Even though the overhead of calling scsi_test_unit_ready() is small for ATA zoned devices, it is much larger for SCSI and it affects performance in a very negative way. Fix this performance regression by executing check_events() only in case of any I/O errors. The function dmz_bdev_is_dying() is modified to call only blk_queue_dying(), while calls to check_events() are made in a new helper function, dmz_check_bdev(). Reported-by: zhangxiaoxu <zhangxiaoxu5@huawei.com> Fixes: 75d66ffb48efb3 ("dm zoned: properly handle backing device failure") Cc: stable@vger.kernel.org Signed-off-by: Dmitry Fomichev <dmitry.fomichev@wdc.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2019-08-15dm zoned: add SPDX license identifiersDmitry Fomichev1-0/+1
Signed-off-by: Dmitry Fomichev <dmitry.fomichev@wdc.com> Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2019-08-15dm zoned: properly handle backing device failureDmitry Fomichev1-0/+10
dm-zoned is observed to lock up or livelock in case of hardware failure or some misconfiguration of the backing zoned device. This patch adds a new dm-zoned target function that checks the status of the backing device. If the request queue of the backing device is found to be in dying state or the SCSI backing device enters offline state, the health check code sets a dm-zoned target flag prompting all further incoming I/O to be rejected. In order to detect backing device failures timely, this new function is called in the request mapping path, at the beginning of every reclaim run and before performing any metadata I/O. The proper way out of this situation is to do dmsetup remove <dm-zoned target> and recreate the target when the problem with the backing device is resolved. Fixes: 3b1a94c88b79 ("dm zoned: drive-managed zoned block device target") Cc: stable@vger.kernel.org Signed-off-by: Dmitry Fomichev <dmitry.fomichev@wdc.com> Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2019-07-17dm zoned: fix zone state management raceDamien Le Moal1-4/+24
dm-zoned uses the zone flag DMZ_ACTIVE to indicate that a zone of the backend device is being actively read or written and so cannot be reclaimed. This flag is set as long as the zone atomic reference counter is not 0. When this atomic is decremented and reaches 0 (e.g. on BIO completion), the active flag is cleared and set again whenever the zone is reused and BIO issued with the atomic counter incremented. These 2 operations (atomic inc/dec and flag set/clear) are however not always executed atomically under the target metadata mutex lock and this causes the warning: WARN_ON(!test_bit(DMZ_ACTIVE, &zone->flags)); in dmz_deactivate_zone() to be displayed. This problem is regularly triggered with xfstests generic/209, generic/300, generic/451 and xfs/077 with XFS being used as the file system on the dm-zoned target device. Similarly, xfstests ext4/303, ext4/304, generic/209 and generic/300 trigger the warning with ext4 use. This problem can be easily fixed by simply removing the DMZ_ACTIVE flag and managing the "ACTIVE" state by directly looking at the reference counter value. To do so, the functions dmz_activate_zone() and dmz_deactivate_zone() are changed to inline functions respectively calling atomic_inc() and atomic_dec(), while the dmz_is_active() macro is changed to an inline function calling atomic_read(). Fixes: 3b1a94c88b79 ("dm zoned: drive-managed zoned block device target") Cc: stable@vger.kernel.org Reported-by: Masato Suzuki <masato.suzuki@wdc.com> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2017-06-19dm zoned: drive-managed zoned block device targetDamien Le Moal1-0/+228
The dm-zoned device mapper target provides transparent write access to zoned block devices (ZBC and ZAC compliant block devices). dm-zoned hides to the device user (a file system or an application doing raw block device accesses) any constraint imposed on write requests by the device, equivalent to a drive-managed zoned block device model. Write requests are processed using a combination of on-disk buffering using the device conventional zones and direct in-place processing for requests aligned to a zone sequential write pointer position. A background reclaim process implemented using dm_kcopyd_copy ensures that conventional zones are always available for executing unaligned write requests. The reclaim process overhead is minimized by managing buffer zones in a least-recently-written order and first targeting the oldest buffer zones. Doing so, blocks under regular write access (such as metadata blocks of a file system) remain stored in conventional zones, resulting in no apparent overhead. dm-zoned implementation focus on simplicity and on minimizing overhead (CPU, memory and storage overhead). For a 14TB host-managed disk with 256 MB zones, dm-zoned memory usage per disk instance is at most about 3 MB and as little as 5 zones will be used internally for storing metadata and performing buffer zone reclaim operations. This is achieved using zone level indirection rather than a full block indirection system for managing block movement between zones. dm-zoned primary target is host-managed zoned block devices but it can also be used with host-aware device models to mitigate potential device-side performance degradation due to excessive random writing. Zoned block devices can be formatted and checked for use with the dm-zoned target using the dmzadm utility available at: https://github.com/hgst/dm-zoned-tools Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com> Reviewed-by: Hannes Reinecke <hare@suse.com> Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com> [Mike Snitzer partly refactored Damien's original work to cleanup the code] Signed-off-by: Mike Snitzer <snitzer@redhat.com>