From e00809a6b6284363f6e48c0fb27b70a4dfd8891a Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Thu, 5 Aug 2021 15:57:33 -0700 Subject: [PATCH] FROMGIT: blk-mq: Introduce the BLK_MQ_F_NO_SCHED_BY_DEFAULT flag 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 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. Signed-off-by: Bart Van Assche Bug: 194450129 (cherry picked from commit 90b7198001f23ea37d3b46dc631bdaa2357a20b1 git://git.kernel.dk/linux-block/ for-5.15/block) Change-Id: I4fb658957c193f350e74bdb5876c20a8f628fcb1 Signed-off-by: Bart Van Assche Signed-off-by: UtsavBalar1231 --- 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 9909aa54a802..616ff6387134 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -984,6 +984,9 @@ int elevator_init_mq(struct request_queue *q) struct elevator_type *e; int err = 0; + if (q->tag_set && q->tag_set->flags & BLK_MQ_F_NO_SCHED_BY_DEFAULT) + return 0; + if (q->nr_hw_queues != 1) return 0; diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index 2885dce1ad49..f78b726f1a72 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -188,7 +188,13 @@ enum { BLK_MQ_F_TAG_SHARED = 1 << 1, BLK_MQ_F_SG_MERGE = 1 << 2, 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,