linux-kernel - [PATCH RFC 2/2] mm: Rework swap handling of zap_pte

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Date:   Wed, 10 Nov 2021 16:29:52 +0800
From:   Peter Xu <peterx@...hat.com>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     peterx@...hat.com, Andrew Morton <akpm@...ux-foundation.org>,
        Yang Shi <shy828301@...il.com>,
        Hugh Dickins <hughd@...gle.com>,
        David Hildenbrand <david@...hat.com>,
        Alistair Popple <apopple@...dia.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A . Shutemov" <kirill@...temov.name>
Subject: [PATCH RFC 2/2] mm: Rework swap handling of zap_pte_range

Clean the code up by merging the device private/exclusive swap entry handling
with the rest, then we merge the pte clear operation too.

struct* page is defined in multiple places in the function, move it upward.

free_swap_and_cache() is only useful for !non_swap_entry() case, put it into
the condition.

No functional change intended.

Signed-off-by: Peter Xu <peterx@...hat.com>
---
 mm/memory.c | 25 ++++++++-----------------
 1 file changed, 8 insertions(+), 17 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index e454f3c6aeb9..e5d59a6b6479 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1326,6 +1326,8 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
 	arch_enter_lazy_mmu_mode();
 	do {
 		pte_t ptent = *pte;
+		struct page *page;
+
 		if (pte_none(ptent))
 			continue;
 
@@ -1333,8 +1335,6 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
 			break;
 
 		if (pte_present(ptent)) {
-			struct page *page;
-
 			page = vm_normal_page(vma, addr, ptent);
 			if (unlikely(zap_skip_check_mapping(details, page)))
 				continue;
@@ -1368,32 +1368,23 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
 		entry = pte_to_swp_entry(ptent);
 		if (is_device_private_entry(entry) ||
 		    is_device_exclusive_entry(entry)) {
-			struct page *page = pfn_swap_entry_to_page(entry);
-
+			page = pfn_swap_entry_to_page(entry);
 			if (unlikely(zap_skip_check_mapping(details, page)))
 				continue;
-			pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
 			rss[mm_counter(page)]--;
-
 			if (is_device_private_entry(entry))
 				page_remove_rmap(page, false);
-
 			put_page(page);
-			continue;
-		}
-
-		if (!non_swap_entry(entry))
-			rss[MM_SWAPENTS]--;
-		else if (is_migration_entry(entry)) {
-			struct page *page;
-
+		} else if (is_migration_entry(entry)) {
 			page = pfn_swap_entry_to_page(entry);
 			if (unlikely(zap_skip_check_mapping(details, page)))
 				continue;
 			rss[mm_counter(page)]--;
+		} else if (!non_swap_entry(entry)) {
+			rss[MM_SWAPENTS]--;
+			if (unlikely(!free_swap_and_cache(entry)))
+				print_bad_pte(vma, addr, ptent, NULL);
 		}
-		if (unlikely(!free_swap_and_cache(entry)))
-			print_bad_pte(vma, addr, ptent, NULL);
 		pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
 	} while (pte++, addr += PAGE_SIZE, addr != end);
 
-- 
2.32.0