linux-kernel - [PATCH 4.14 04/25] mm/rmap: use page_not_mapped in try_to

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Date:   Fri,  9 Jul 2021 15:18:35 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Miaohe Lin <linmiaohe@...wei.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.14 04/25] mm/rmap: use page_not_mapped in try_to_unmap()

From: Miaohe Lin <linmiaohe@...wei.com>

[ Upstream commit b7e188ec98b1644ff70a6d3624ea16aadc39f5e0 ]

page_mapcount_is_zero() calculates accurately how many mappings a hugepage
has in order to check against 0 only.  This is a waste of cpu time.  We
can do this via page_not_mapped() to save some possible atomic_read
cycles.  Remove the function page_mapcount_is_zero() as it's not used
anymore and move page_not_mapped() above try_to_unmap() to avoid
identifier undeclared compilation error.

Link: https://lkml.kernel.org/r/20210130084904.35307-1-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 mm/rmap.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/mm/rmap.c b/mm/rmap.c
index e2506b6adb6a..e6a556fec9d1 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1624,9 +1624,9 @@ static bool invalid_migration_vma(struct vm_area_struct *vma, void *arg)
 	return is_vma_temporary_stack(vma);
 }
 
-static int page_mapcount_is_zero(struct page *page)
+static int page_not_mapped(struct page *page)
 {
-	return !total_mapcount(page);
+	return !page_mapped(page);
 }
 
 /**
@@ -1644,7 +1644,7 @@ bool try_to_unmap(struct page *page, enum ttu_flags flags)
 	struct rmap_walk_control rwc = {
 		.rmap_one = try_to_unmap_one,
 		.arg = (void *)flags,
-		.done = page_mapcount_is_zero,
+		.done = page_not_mapped,
 		.anon_lock = page_lock_anon_vma_read,
 	};
 
@@ -1668,11 +1668,6 @@ bool try_to_unmap(struct page *page, enum ttu_flags flags)
 	return !page_mapcount(page) ? true : false;
 }
 
-static int page_not_mapped(struct page *page)
-{
-	return !page_mapped(page);
-}
-
 /**
  * try_to_munlock - try to munlock a page
  * @page: the page to be munlocked
-- 
2.30.2