Commit a500cb34 authored by Miaohe Lin's avatar Miaohe Lin Committed by Linus Torvalds
Browse files

mm/page_isolation: guard against possible putback unisolated page 

Isolating a free page in an isolated pageblock is expected to always
work as watermarks don't apply here.

But if __isolate_free_page() failed, due to condition changes, the page
will be left on the free list.  And the page will be put back to free
list again via __putback_isolated_page().  This may trigger
VM_BUG_ON_PAGE() on page->flags checking in __free_one_page() if
PageReported is set.  Or we will corrupt the free list because
list_add() will be called for pages already on another list.

Add a VM_WARN_ON() to complain about this change.

Link: https://lkml.kernel.org/r/20210914114508.23725-1-linmiaohe@huawei.com


Fixes: 3c605096 ("mm/page_alloc: restrict max order of merging on isolated pageblock")
Signed-off-by: default avatarMiaohe Lin <linmiaohe@huawei.com>
Reviewed-by: default avatarDavid Hildenbrand <david@redhat.com>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e1d8c966

mm/page_isolation.c

+7 −2
Original line number Diff line number Diff line
@@ -94,8 +94,13 @@ static void unset_migratetype_isolate(struct page *page, unsigned migratetype) 
			buddy = page + (buddy_pfn - pfn);



			if (!is_migrate_isolate_page(buddy)) {

				__isolate_free_page(page, order);

				isolated_page = true;

				isolated_page = !!__isolate_free_page(page, order);

				/*

				 * Isolating a free page in an isolated pageblock

				 * is expected to always work as watermarks don't

				 * apply here.

				 */

				VM_WARN_ON(!isolated_page);

			}

		}

	}