linux-kernel - [PATCH 1/4] mm/rmap: fix comments left over from recent changes

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Date:   Wed, 7 Jul 2021 13:06:17 -0700 (PDT)
From:   Hugh Dickins <hughd@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
cc:     Hugh Dickins <hughd@...gle.com>,
        Alistair Popple <apopple@...dia.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Ralph Campbell <rcampbell@...dia.com>,
        Christoph Hellwig <hch@....de>, Yang Shi <shy828301@...il.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH 1/4] mm/rmap: fix comments left over from recent changes

Parallel developments in mm/rmap.c have left behind some out-of-date
comments: try_to_migrate_one() also accepts TTU_SYNC (already commented
in try_to_migrate() itself), and try_to_migrate() returns nothing at all.

TTU_SPLIT_FREEZE has just been deleted, so reword the comment about it in
mm/huge_memory.c; and TTU_IGNORE_ACCESS was removed in 5.11, so delete
the "recently referenced" comment from try_to_unmap_one() (once upon a
time the comment was near the removed codeblock, but they drifted apart).

Signed-off-by: Hugh Dickins <hughd@...gle.com>
---
 mm/huge_memory.c | 2 +-
 mm/rmap.c        | 7 +------
 2 files changed, 2 insertions(+), 7 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 8b731d53e9f4..afff3ac87067 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2331,7 +2331,7 @@ static void remap_page(struct page *page, unsigned int nr)
 {
 	int i;
 
-	/* If TTU_SPLIT_FREEZE is ever extended to file, remove this check */
+	/* If unmap_page() uses try_to_migrate() on file, remove this check */
 	if (!PageAnon(page))
 		return;
 	if (PageTransHuge(page)) {
diff --git a/mm/rmap.c b/mm/rmap.c
index 37c24672125c..746013e282c3 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1439,8 +1439,6 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
 	while (page_vma_mapped_walk(&pvmw)) {
 		/*
 		 * If the page is mlock()d, we cannot swap it out.
-		 * If it's recently referenced (perhaps page_referenced
-		 * skipped over this mm) then we should reactivate it.
 		 */
 		if (!(flags & TTU_IGNORE_MLOCK)) {
 			if (vma->vm_flags & VM_LOCKED) {
@@ -1687,8 +1685,7 @@ void try_to_unmap(struct page *page, enum ttu_flags flags)
  * @arg: enum ttu_flags will be passed to this argument.
  *
  * If TTU_SPLIT_HUGE_PMD is specified any PMD mappings will be split into PTEs
- * containing migration entries. This and TTU_RMAP_LOCKED are the only supported
- * flags.
+ * containing migration entries.
  */
 static bool try_to_migrate_one(struct page *page, struct vm_area_struct *vma,
 		     unsigned long address, void *arg)
@@ -1928,8 +1925,6 @@ static bool try_to_migrate_one(struct page *page, struct vm_area_struct *vma,
  *
  * Tries to remove all the page table entries which are mapping this page and
  * replace them with special swap entries. Caller must hold the page lock.
- *
- * If is successful, return true. Otherwise, false.
  */
 void try_to_migrate(struct page *page, enum ttu_flags flags)
 {
-- 
2.26.2