Commit aaa9705b authored by Miaohe Lin's avatar Miaohe Lin Committed by Linus Torvalds
Browse files

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: default avatarMiaohe Lin <linmiaohe@huawei.com>
Reviewed-by: default avatarZi Yan <ziy@nvidia.com>
Reviewed-by: default avatarPeter 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 71f9e58e

mm/huge_memory.c

+4 −4
Original line number Diff line number Diff line
@@ -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)