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

Hugh Dickins
2021-07-07T20:06:44Z

Parallel developments in mm/rmap.c have left behind some out-of-date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@google.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