linux-kernel - [PATCH] mm, trivial: Simplify swap related code in try_to_unmap

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Message-Id: <20200331084613.1258555-1-ying.huang@intel.com>
Date:   Tue, 31 Mar 2020 16:46:13 +0800
From:   "Huang, Ying" <ying.huang@...el.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Huang Ying <ying.huang@...el.com>,
        Michal Hocko <mhocko@...nel.org>,
        Minchan Kim <minchan@...nel.org>,
        Hugh Dickins <hughd@...gle.com>,
        Rik van Riel <riel@...riel.com>
Subject: [PATCH] mm, trivial: Simplify swap related code in try_to_unmap_one()

From: Huang Ying <ying.huang@...el.com>

Because PageSwapCache() will always return false if PageSwapBacked() returns
false, and PageSwapBacked() will be check for MADV_FREE pages in
try_to_unmap_one().  The swap related code in try_to_unmap_one() can be
simplified to improve the readability.

Signed-off-by: "Huang, Ying" <ying.huang@...el.com>
Cc: Michal Hocko <mhocko@...nel.org>
Cc: Minchan Kim <minchan@...nel.org>
Cc: Hugh Dickins <hughd@...gle.com>
Cc: Rik van Riel <riel@...riel.com>
---
 mm/rmap.c | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/mm/rmap.c b/mm/rmap.c
index 2126fd4a254b..cd3c406aeac7 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1613,19 +1613,6 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
 		} else if (PageAnon(page)) {
 			swp_entry_t entry = { .val = page_private(subpage) };
 			pte_t swp_pte;
-			/*
-			 * Store the swap location in the pte.
-			 * See handle_pte_fault() ...
-			 */
-			if (unlikely(PageSwapBacked(page) != PageSwapCache(page))) {
-				WARN_ON_ONCE(1);
-				ret = false;
-				/* We have to invalidate as we cleared the pte */
-				mmu_notifier_invalidate_range(mm, address,
-							address + PAGE_SIZE);
-				page_vma_mapped_walk_done(&pvmw);
-				break;
-			}
 
 			/* MADV_FREE page check */
 			if (!PageSwapBacked(page)) {
@@ -1648,6 +1635,20 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
 				break;
 			}
 
+			/*
+			 * Store the swap location in the pte.
+			 * See handle_pte_fault() ...
+			 */
+			if (unlikely(!PageSwapCache(page))) {
+				WARN_ON_ONCE(1);
+				ret = false;
+				/* We have to invalidate as we cleared the pte */
+				mmu_notifier_invalidate_range(mm, address,
+							address + PAGE_SIZE);
+				page_vma_mapped_walk_done(&pvmw);
+				break;
+			}
+
 			if (swap_duplicate(entry) < 0) {
 				set_pte_at(mm, address, pvmw.pte, pteval);
 				ret = false;
-- 
2.25.0