From: Bart Van Assche <bvanassche@acm.org> mainline inclusion from mainline-5.15-rc1 commit 90b7198001f23ea37d3b46dc631bdaa2357a20b1 category: performance issue: #I4NRS5 CVE: NA Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... Signed-off-by: Yu Changchun <yuchangchun1@huawei.com> --------------------------- elevator_get_default() uses the following algorithm to select an I/O scheduler from inside add_disk(): - In case of a single hardware queue or if sharing hardware queues across multiple request queues (BLK_MQ_F_TAG_HCTX_SHARED), use mq-deadline. - Otherwise, use 'none'. This is a good choice for most but not for all block drivers. Make it possible to override the selection of mq-deadline with a new flag, namely BLK_MQ_F_NO_SCHED_BY_DEFAULT. Cc: Christoph Hellwig <hch@lst.de> Cc: Ming Lei <ming.lei@redhat.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: Martijn Coenen <maco@android.com> Cc: Jaegeuk Kim <jaegeuk@kernel.org> Signed-off-by: Bart Van Assche <bvanassche@acm.org> Link: https://lore.kernel.org/r/20210805174200.3250718-2-bvanassche@acm.org Signed-off-by: Jens Axboe <axboe@kernel.dk> Conflicts: block/elevator.c Signed-off-by: yangerkun <yangerkun@huawei.com> Reviewed-by: Jason Yan <yanaijie@huawei.com> Signed-off-by: Chen Jun <chenjun102@huawei.com> Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com> Signed-off-by: Yu Changchun <yuchangchun1@huawei.com> --- block/elevator.c | 3 +++ include/linux/blk-mq.h | 6 ++++++ 2 files changed, 9 insertions(+) diff --git a/block/elevator.c b/block/elevator.c index 2a525863d4e9..4ce6b22813a1 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -624,6 +624,9 @@ static inline bool elv_support_iosched(struct request_queue *q) */ static struct elevator_type *elevator_get_default(struct request_queue *q) { + if (q->tag_set && q->tag_set->flags & BLK_MQ_F_NO_SCHED_BY_DEFAULT) + return NULL; + if (q->nr_hw_queues != 1) return NULL; diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index 92bbc9a72355..eee2c8a16601 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -399,7 +399,13 @@ enum { BLK_MQ_F_STACKING = 1 << 2, BLK_MQ_F_TAG_HCTX_SHARED = 1 << 3, BLK_MQ_F_BLOCKING = 1 << 5, + /* Do not allow an I/O scheduler to be configured. */ BLK_MQ_F_NO_SCHED = 1 << 6, + /* + * Select 'none' during queue registration in case of a single hwq + * or shared hwqs instead of 'mq-deadline'. + */ + BLK_MQ_F_NO_SCHED_BY_DEFAULT = 1 << 7, BLK_MQ_F_ALLOC_POLICY_START_BIT = 8, BLK_MQ_F_ALLOC_POLICY_BITS = 1, -- 2.25.1