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Commit 2def7424 authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
Browse files

mm: page migration use the put_new_page whenever necessary 



I don't know of any problem from the way it's used in our current tree,
but there is one defect in page migration's custom put_new_page feature.

An unused newpage is expected to be released with the put_new_page(), but
there was one MIGRATEPAGE_SUCCESS (0) path which released it with
putback_lru_page(): which can be very wrong for a custom pool.

Fixed more easily by resetting put_new_page once it won't be needed, than
by adding a further flag to modify the rc test.

Signed-off-by: default avatarHugh Dickins <hughd@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Rik van Riel <riel@redhat.com>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 14e0f9bc

mm/migrate.c

+11 −8
Original line number Diff line number Diff line
@@ -938,10 +938,11 @@ static ICE_noinline int unmap_and_move(new_page_t get_new_page, 
				   int force, enum migrate_mode mode,

				   enum migrate_reason reason)

{

	int rc = 0;

	int rc = MIGRATEPAGE_SUCCESS;

	int *result = NULL;

	struct page *newpage = get_new_page(page, private, &result);

	struct page *newpage;



	newpage = get_new_page(page, private, &result);

	if (!newpage)

		return -ENOMEM;
@@ -955,6 +956,8 @@ static ICE_noinline int unmap_and_move(new_page_t get_new_page, 
			goto out;



	rc = __unmap_and_move(page, newpage, force, mode);

	if (rc == MIGRATEPAGE_SUCCESS)

		put_new_page = NULL;



out:

	if (rc != -EAGAIN) {
@@ -981,7 +984,7 @@ static ICE_noinline int unmap_and_move(new_page_t get_new_page, 
	 * it.  Otherwise, putback_lru_page() will drop the reference grabbed

	 * during isolation.

	 */

	if (rc != MIGRATEPAGE_SUCCESS && put_new_page) {

	if (put_new_page) {

		ClearPageSwapBacked(newpage);

		put_new_page(newpage, private);

	} else if (unlikely(__is_movable_balloon_page(newpage))) {
@@ -1022,7 +1025,7 @@ static int unmap_and_move_huge_page(new_page_t get_new_page, 
				struct page *hpage, int force,

				enum migrate_mode mode)

{

	int rc = 0;

	int rc = -EAGAIN;

	int *result = NULL;

	int page_was_mapped = 0;

	struct page *new_hpage;
@@ -1044,8 +1047,6 @@ static int unmap_and_move_huge_page(new_page_t get_new_page, 
	if (!new_hpage)

		return -ENOMEM;



	rc = -EAGAIN;



	if (!trylock_page(hpage)) {

		if (!force || mode != MIGRATE_SYNC)

			goto out;
@@ -1070,8 +1071,10 @@ static int unmap_and_move_huge_page(new_page_t get_new_page, 
	if (anon_vma)

		put_anon_vma(anon_vma);



	if (rc == MIGRATEPAGE_SUCCESS)

	if (rc == MIGRATEPAGE_SUCCESS) {

		hugetlb_cgroup_migrate(hpage, new_hpage);

		put_new_page = NULL;

	}



	unlock_page(hpage);

out:
@@ -1083,7 +1086,7 @@ static int unmap_and_move_huge_page(new_page_t get_new_page, 
	 * it.  Otherwise, put_page() will drop the reference grabbed during

	 * isolation.

	 */

	if (rc != MIGRATEPAGE_SUCCESS && put_new_page)

	if (put_new_page)

		put_new_page(new_hpage, private);

	else

		putback_active_hugepage(new_hpage);