From: Jens Axboe <axboe@kernel.dk>
Date: Mon, 18 Oct 2021 10:08:49 -0600
Subject: [PATCH] block: get rid of plug list sorting
Git-commit: df87eb0fce8fc891b43199447b9aeb3ea2d39bcf
Patch-mainline: v5.16-rc1
References: jsc#PED-1183

Even if we have multiple queues in the plug list, chances that they
are very interspersed is minimal. Don't bother spending CPU cycles
sorting the list.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Hannes Reinecke <hare@suse.com>
---
 block/blk-mq.c | 19 -------------------
 1 file changed, 19 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 335ec3a7eab7..104019c0ea41 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -19,7 +19,6 @@
 #include <linux/smp.h>
 #include <linux/interrupt.h>
 #include <linux/llist.h>
-#include <linux/list_sort.h>
 #include <linux/cpu.h>
 #include <linux/cache.h>
 #include <linux/sched/sysctl.h>
@@ -2161,20 +2160,6 @@ void blk_mq_insert_requests(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx,
 	spin_unlock(&ctx->lock);
 }
 
-static int plug_rq_cmp(void *priv, const struct list_head *a,
-		       const struct list_head *b)
-{
-	struct request *rqa = container_of(a, struct request, queuelist);
-	struct request *rqb = container_of(b, struct request, queuelist);
-
-	if (rqa->mq_ctx != rqb->mq_ctx)
-		return rqa->mq_ctx > rqb->mq_ctx;
-	if (rqa->mq_hctx != rqb->mq_hctx)
-		return rqa->mq_hctx > rqb->mq_hctx;
-
-	return blk_rq_pos(rqa) > blk_rq_pos(rqb);
-}
-
 void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
 {
 	LIST_HEAD(list);
@@ -2182,10 +2167,6 @@ void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
 	if (list_empty(&plug->mq_list))
 		return;
 	list_splice_init(&plug->mq_list, &list);
-
-	if (plug->rq_count > 2 && plug->multiple_queues)
-		list_sort(NULL, &list, plug_rq_cmp);
-
 	plug->rq_count = 0;
 
 	do {
-- 
2.35.3