From 68c43f133a754c7bf5cb1018bb16dc0821cc43a1 Mon Sep 17 00:00:00 2001 From: Damien Le Moal Date: Thu, 5 Sep 2019 18:51:31 +0900 Subject: block: Introduce elevator features Introduce the definition of elevator features through the elevator_features flags in the elevator_type structure. Each flag can represent a feature supported by an elevator. The first feature defined by this patch is support for zoned block device sequential write constraint with the flag ELEVATOR_F_ZBD_SEQ_WRITE, which is implemented by the mq-deadline elevator using zone write locking. Other possible features are IO priorities, write hints, latency targets or single-LUN dual-actuator disks (for which the elevator could maintain one LBA ordered list per actuator). The required_elevator_features field is also added to the request_queue structure to allow a device driver to specify elevator feature flags that an elevator must support for the correct operation of the device (e.g. device drivers for zoned block devices can have the ELEVATOR_F_ZBD_SEQ_WRITE flag as a required feature). The helper function blk_queue_required_elevator_features() is defined for setting this new field. With these two new fields in place, the elevator functions elevator_match() and elevator_find() are modified to allow a user to set only an elevator with a set of features that satisfies the device required features. Elevators not matching the device requirements are not shown in the device sysfs queue/scheduler file to prevent their use. The "none" elevator can always be selected as before. Reviewed-by: Johannes Thumshirn Reviewed-by: Christoph Hellwig Reviewed-by: Ming Lei Signed-off-by: Damien Le Moal Signed-off-by: Jens Axboe --- include/linux/blkdev.h | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'include/linux/blkdev.h') diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index d0ad21e4771b..b196124e3240 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -496,6 +496,8 @@ struct request_queue { struct queue_limits limits; + unsigned int required_elevator_features; + #ifdef CONFIG_BLK_DEV_ZONED /* * Zoned block device information for request dispatch control. @@ -1097,6 +1099,8 @@ extern void blk_queue_dma_alignment(struct request_queue *, int); extern void blk_queue_update_dma_alignment(struct request_queue *, int); extern void blk_queue_rq_timeout(struct request_queue *, unsigned int); extern void blk_queue_write_cache(struct request_queue *q, bool enabled, bool fua); +extern void blk_queue_required_elevator_features(struct request_queue *q, + unsigned int features); /* * Number of physical segments as sent to the device. -- cgit v1.2.3