linux-kernel - [PATCH 15/16] block: use __this_cpu_add() instead of access by smp_processor

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Date:   Wed, 27 May 2020 07:24:18 +0200
From:   Christoph Hellwig <hch@....de>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        Minchan Kim <minchan@...nel.org>,
        Nitin Gupta <ngupta@...are.org>, dm-devel@...hat.com,
        linux-block@...r.kernel.org, drbd-dev@...ts.linbit.com,
        linux-bcache@...r.kernel.org, linux-nvdimm@...ts.01.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 15/16] block: use __this_cpu_add() instead of access by smp_processor_id()

From: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>

Most architectures have fast path to access percpu for current cpu.
The required preempt_disable() is provided by part_stat_lock().

Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
[hch: rebased]
Signed-off-by: Christoph Hellwig <hch@....de>
---
 include/linux/part_stat.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/part_stat.h b/include/linux/part_stat.h
index a6b0938ce82e9..24125778ef3ec 100644
--- a/include/linux/part_stat.h
+++ b/include/linux/part_stat.h
@@ -54,7 +54,7 @@ static inline void part_stat_set_all(struct hd_struct *part, int value)
 	 part_stat_read(part, field[STAT_DISCARD]))
 
 #define __part_stat_add(part, field, addnd)				\
-	(part_stat_get(part, field) += (addnd))
+	__this_cpu_add((part)->dkstats->field, addnd)
 
 #define part_stat_add(part, field, addnd)	do {			\
 	__part_stat_add((part), field, addnd);				\
-- 
2.26.2