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Message-ID: <20210316124007.20474-3-linmiaohe@huawei.com>
Date: Tue, 16 Mar 2021 08:40:03 -0400
From: Miaohe Lin <linmiaohe@...wei.com>
To: <akpm@...ux-foundation.org>
CC: <ziy@...dia.com>, <willy@...radead.org>,
<william.kucharski@...cle.com>, <vbabka@...e.cz>,
<peterx@...hat.com>, <yulei.kernel@...il.com>, <walken@...gle.com>,
<aneesh.kumar@...ux.ibm.com>, <rcampbell@...dia.com>,
<thomas_os@...pmail.org>, <yang.shi@...ux.alibaba.com>,
<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
<linmiaohe@...wei.com>
Subject: [PATCH v2 2/6] mm/huge_memory.c: make get_huge_zero_page() return bool
It's guaranteed that huge_zero_page will not be NULL if huge_zero_refcount
is increased successfully. When READ_ONCE(huge_zero_page) is returned,
there must be a huge_zero_page and it can be replaced with returning 'true'
when we do not care about the value of huge_zero_page. We can thus make it
return bool to save READ_ONCE cpu cycles as the return value is just used
to check if huge_zero_page exists.
Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
---
mm/huge_memory.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index e943ccbdc9dd..caad9942c693 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -77,18 +77,18 @@ bool transparent_hugepage_enabled(struct vm_area_struct *vma)
return false;
}
-static struct page *get_huge_zero_page(void)
+static bool get_huge_zero_page(void)
{
struct page *zero_page;
retry:
if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
- return READ_ONCE(huge_zero_page);
+ return true;
zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
HPAGE_PMD_ORDER);
if (!zero_page) {
count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
- return NULL;
+ return false;
}
count_vm_event(THP_ZERO_PAGE_ALLOC);
preempt_disable();
@@ -101,7 +101,7 @@ static struct page *get_huge_zero_page(void)
/* We take additional reference here. It will be put back by shrinker */
atomic_set(&huge_zero_refcount, 2);
preempt_enable();
- return READ_ONCE(huge_zero_page);
+ return true;
}
static void put_huge_zero_page(void)
--
2.19.1
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