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authorDamien Le Moal <damien.lemoal@wdc.com>2021-06-18 04:59:22 +0300
committerJens Axboe <axboe@kernel.dk>2021-06-18 17:51:48 +0300
commite42cfb1da0bf33c313318da201730324c423351d (patch)
tree53fc872475028ef3bce42e418c791c2ede206f4d /block/elevator.c
parentf0c1c4d2864ed614f90d2da1bab1a1c42907b940 (diff)
downloadlinux-e42cfb1da0bf33c313318da201730324c423351d.tar.xz
block: Remove unnecessary elevator operation checks
The insert_requests and dispatch_request elevator operations are mandatory for the correct execution of an elevator, and all implemented elevators (bfq, kyber and mq-deadline) implement them. As a result, there is no need to check for these operations before calling them when a queue has an elevator set. This simplifies the code in __blk_mq_sched_dispatch_requests() and blk_mq_sched_insert_request(). To avoid out-of-tree elevators to crash the kernel in case of bad implementation, add a check in elv_register() to verify that these operations are implemented. A small, probably not significant, IOPS improvement of 0.1% is observed with this patch applied (4.117 MIOPS to 4.123 MIOPS, average of 20 fio runs doing 4K random direct reads with psync and 32 jobs). Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Link: https://lore.kernel.org/r/20210618015922.713999-1-damien.lemoal@wdc.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/elevator.c')
-rw-r--r--block/elevator.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/block/elevator.c b/block/elevator.c
index 06e203426410..85d0d4adbb64 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -522,6 +522,10 @@ void elv_unregister_queue(struct request_queue *q)
int elv_register(struct elevator_type *e)
{
+ /* insert_requests and dispatch_request are mandatory */
+ if (WARN_ON_ONCE(!e->ops.insert_requests || !e->ops.dispatch_request))
+ return -EINVAL;
+
/* create icq_cache if requested */
if (e->icq_size) {
if (WARN_ON(e->icq_size < sizeof(struct io_cq)) ||