This patch series implements some cleanup of the elevator initialization code and introduces elevator features identification and device matching to enhance checks for elevator/device compatibility and fitness. The first 2 patches of the series are simple cleanups which simplify elevator initialization for newly allocated device queues. Patch 3 introduce elevator features, allowing a clean and extensible definition of devices and features that an elevator supports and match these against features required by a block device. With this, the sysfs elevator list for a device always shows only elevators matching the features that a particular device requires, with the exception of the none elevator which has no features but is always available for use with any device. The first feature defined is for zoned block device sequential write constraint support through zone write locking which prevents the use of any elevator that does not support this feature with zoned devices. The last 4 patches of this series rework the default elevator selection and initialization to allow for the elevator/device features matching to work, doing so addressing cases not currently well supported, namely, multi-queue zoned block devices. Damien Le Moal (7): block: Cleanup elevator_init_mq() use block: Change elevator_init_mq() to always succeed block: Introduce elevator features block: Improve default elevator selection block: Delay default elevator initialization block: Set ELEVATOR_F_ZBD_SEQ_WRITE for nullblk zoned disks scsi: Set ELEVATOR_F_ZBD_SEQ_WRITE for ZBC disks block/blk-mq.c | 10 --- block/blk-settings.c | 16 ++++ block/blk.h | 2 +- block/elevator.c | 138 ++++++++++++++++++++++++++-------- block/genhd.c | 3 + block/mq-deadline.c | 1 + drivers/block/null_blk_main.c | 2 + drivers/scsi/sd_zbc.c | 2 + include/linux/blkdev.h | 4 + include/linux/elevator.h | 8 ++ 10 files changed, 145 insertions(+), 41 deletions(-) -- 2.21.0
