From 844fc27af6308dc2acff909152bf2426076e3ccc Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Mon, 28 Jun 2021 16:59:07 +0200
Subject: [PATCH 1/4] block: Provide blk_mq_sched_get_icq()
References: bsc#1184318
Patch-mainline: Not yet, in linux-block tree as of 21/12/2021

Currently we lookup ICQ only after the request is allocated. However BFQ
will want to decide how many scheduler tags it allows a given bfq queue
(effectively a process) to consume based on cgroup weight. So provide a
function blk_mq_sched_get_icq() so that BFQ can lookup ICQ earlier.

Acked-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jan Kara <jack@suse.cz>
---
 block/blk-mq-sched.c |   26 +++++++++++++++-----------
 block/blk-mq-sched.h |    1 +
 2 files changed, 16 insertions(+), 11 deletions(-)

--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -33,28 +33,32 @@ void blk_mq_sched_free_hctx_data(struct
 }
 EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data);
 
-void blk_mq_sched_assign_ioc(struct request *rq)
+struct io_cq *blk_mq_sched_get_icq(struct request_queue *q)
 {
-	struct request_queue *q = rq->q;
 	struct io_context *ioc;
 	struct io_cq *icq;
 
-	/*
-	 * May not have an IO context if it's a passthrough request
-	 */
+	/* May not have an IO context if context creation failed */
 	ioc = current->io_context;
 	if (!ioc)
-		return;
+		return NULL;
 
 	spin_lock_irq(&q->queue_lock);
 	icq = ioc_lookup_icq(ioc, q);
 	spin_unlock_irq(&q->queue_lock);
+	if (icq)
+		return icq;
+	return ioc_create_icq(ioc, q, GFP_ATOMIC);
+}
+EXPORT_SYMBOL(blk_mq_sched_get_icq);
+
+void blk_mq_sched_assign_ioc(struct request *rq)
+{
+	struct io_cq *icq;
 
-	if (!icq) {
-		icq = ioc_create_icq(ioc, q, GFP_ATOMIC);
-		if (!icq)
-			return;
-	}
+	icq = blk_mq_sched_get_icq(rq->q);
+	if (!icq)
+		return;
 	get_io_context(icq->ioc);
 	rq->elv.icq = icq;
 }
--- a/block/blk-mq-sched.h
+++ b/block/blk-mq-sched.h
@@ -8,6 +8,7 @@
 void blk_mq_sched_free_hctx_data(struct request_queue *q,
 				 void (*exit)(struct blk_mq_hw_ctx *));
 
+struct io_cq *blk_mq_sched_get_icq(struct request_queue *q);
 void blk_mq_sched_assign_ioc(struct request *rq);
 
 void blk_mq_sched_request_inserted(struct request *rq);