diff mbox series

[023/143] mm/huge_memory.c: make get_huge_zero_page() return bool

Message ID 20210505013355.k_z4wGMq9%akpm@linux-foundation.org (mailing list archive)
State New
Headers show
Series [001/143] mm: introduce and use mapping_empty() | expand

Commit Message

Andrew Morton May 5, 2021, 1:33 a.m. UTC
From: Miaohe Lin <linmiaohe@huawei.com>
Subject: 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.

Link: https://lkml.kernel.org/r/20210318122722.13135-3-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michel Lespinasse <walken@google.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Thomas Hellstrm (Intel) <thomas_os@shipmail.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: William Kucharski <william.kucharski@oracle.com>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Cc: yuleixzhang <yulei.kernel@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/huge_memory.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)
diff mbox series

Patch

--- a/mm/huge_memory.c~mm-huge_memoryc-make-get_huge_zero_page-return-bool
+++ a/mm/huge_memory.c
@@ -77,18 +77,18 @@  bool transparent_hugepage_enabled(struct
 	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 @@  retry:
 	/* 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)