linux-kernel - [PATCH 3/5] mm: khugepaged: support shmem mTHP copy

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Message-Id: <938e8cc5a15f841fdd343d324d8a6dd989cd52e0.1724054125.git.baolin.wang@linux.alibaba.com>
Date: Mon, 19 Aug 2024 16:14:04 +0800
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: akpm@...ux-foundation.org
Cc: hughd@...gle.com,
	willy@...radead.org,
	david@...hat.com,
	21cnbao@...il.com,
	ryan.roberts@....com,
	shy828301@...il.com,
	ziy@...dia.com,
	baolin.wang@...ux.alibaba.com,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 3/5] mm: khugepaged: support shmem mTHP copy

Iterate each subpage in the large folio to copy, as preparation for supporting
shmem mTHP collapse.

Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
---
 mm/khugepaged.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 60d95f08610c..91ee672db202 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -2060,17 +2060,22 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
 	index = start;
 	dst = folio_page(new_folio, 0);
 	list_for_each_entry(folio, &pagelist, lru) {
+		int i, nr_pages = folio_nr_pages(folio);
+
 		while (index < folio->index) {
 			clear_highpage(dst);
 			index++;
 			dst++;
 		}
-		if (copy_mc_highpage(dst, folio_page(folio, 0)) > 0) {
-			result = SCAN_COPY_MC;
-			goto rollback;
+
+		for (i = 0; i < nr_pages; i++) {
+			if (copy_mc_highpage(dst, folio_page(folio, i)) > 0) {
+				result = SCAN_COPY_MC;
+				goto rollback;
+			}
+			index++;
+			dst++;
 		}
-		index++;
-		dst++;
 	}
 	while (index < end) {
 		clear_highpage(dst);
-- 
2.39.3