[PATCH v2 4/4] mm: Remove managed_page_count spinlock

From: Arun KS <arunks@codeaurora.org>
To: akpm@linux-foundation.org, keescook@chromium.org,
	khlebnikov@yandex-team.ru, minchan@kernel.org, mhocko@kernel.org,
	vbabka@suse.cz, osalvador@suse.de, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org
Cc: getarunks@gmail.com, Arun KS <arunks@codeaurora.org>
Subject: [PATCH v2 4/4] mm: Remove managed_page_count spinlock
Date: Tue,  6 Nov 2018 21:51:50 +0530	[thread overview]
Message-ID: <1541521310-28739-5-git-send-email-arunks@codeaurora.org> (raw)
In-Reply-To: <1541521310-28739-1-git-send-email-arunks@codeaurora.org>

Now totalram_pages and managed_pages are atomic varibles. No need
of managed_page_count spinlock.

Signed-off-by: Arun KS <arunks@codeaurora.org>
Reviewed-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Acked-by: Michal Hocko <mhocko@suse.com>
---
 include/linux/mmzone.h | 6 ------
 mm/page_alloc.c        | 5 -----
 2 files changed, 11 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index e73dc31..c71b4d9 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -428,12 +428,6 @@ struct zone {
 	 * Write access to present_pages at runtime should be protected by
 	 * mem_hotplug_begin/end(). Any reader who can't tolerant drift of
 	 * present_pages should get_online_mems() to get a stable value.
-	 *
-	 * Read access to managed_pages should be safe because it's unsigned
-	 * long. Write access to zone->managed_pages and totalram_pages are
-	 * protected by managed_page_count_lock at runtime. Idealy only
-	 * adjust_managed_page_count() should be used instead of directly
-	 * touching zone->managed_pages and totalram_pages.
 	 */
 	atomic_long_t		managed_pages;
 	unsigned long		spanned_pages;
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2a42c3f..4d78bde 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -122,9 +122,6 @@
 };
 EXPORT_SYMBOL(node_states);
 
-/* Protect totalram_pages and zone->managed_pages */
-static DEFINE_SPINLOCK(managed_page_count_lock);
-
 atomic_long_t _totalram_pages __read_mostly;
 unsigned long totalreserve_pages __read_mostly;
 unsigned long totalcma_pages __read_mostly;
@@ -7064,14 +7061,12 @@ static int __init cmdline_parse_movablecore(char *p)
 
 void adjust_managed_page_count(struct page *page, long count)
 {
-	spin_lock(&managed_page_count_lock);
 	atomic_long_add(count, &page_zone(page)->managed_pages);
 	totalram_pages_add(count);
 #ifdef CONFIG_HIGHMEM
 	if (PageHighMem(page))
 		totalhigh_pages_add(count);
 #endif
-	spin_unlock(&managed_page_count_lock);
 }
 EXPORT_SYMBOL(adjust_managed_page_count);
 
-- 
1.9.1

