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| author | Damien Le Moal <damien.lemoal@wdc.com> | 2021-06-18 10:59:22 +0900 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2021-06-18 08:51:48 -0600 |
| commit | e42cfb1da0bf33c313318da201730324c423351d (patch) | |
| tree | 53fc872475028ef3bce42e418c791c2ede206f4d /block/elevator.c | |
| parent | f0c1c4d2864ed614f90d2da1bab1a1c42907b940 (diff) | |
| download | lwn-e42cfb1da0bf33c313318da201730324c423351d.tar.gz lwn-e42cfb1da0bf33c313318da201730324c423351d.zip | |
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.c | 4 |
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)) || |