Commit b2926ac8 authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle) Committed by Andrew Morton
Browse files

mm: remove stale example from comment 

folio_add_new_anon_rmap() no longer works this way, so just remove the
entire example.

Link: https://lkml.kernel.org/r/20231211162214.2146080-6-willy@infradead.org


Signed-off-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: default avatarDavid Hildenbrand <david@redhat.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 2853b66b

mm/memremap.c

+4 −14
Original line number Diff line number Diff line
@@ -473,21 +473,11 @@ void free_zone_device_page(struct page *page) 
		__ClearPageAnonExclusive(page);



	/*

	 * When a device managed page is freed, the page->mapping field

	 * When a device managed page is freed, the folio->mapping field

	 * may still contain a (stale) mapping value. For example, the

	 * lower bits of page->mapping may still identify the page as an

	 * anonymous page. Ultimately, this entire field is just stale

	 * and wrong, and it will cause errors if not cleared.  One

	 * example is:

	 *

	 *  migrate_vma_pages()

	 *    migrate_vma_insert_page()

	 *      page_add_new_anon_rmap()

	 *        __page_set_anon_rmap()

	 *          ...checks page->mapping, via PageAnon(page) call,

	 *            and incorrectly concludes that the page is an

	 *            anonymous page. Therefore, it incorrectly,

	 *            silently fails to set up the new anon rmap.

	 * lower bits of folio->mapping may still identify the folio as an

	 * anonymous folio. Ultimately, this entire field is just stale

	 * and wrong, and it will cause errors if not cleared.

	 *

	 * For other types of ZONE_DEVICE pages, migration is either

	 * handled differently or not done at all, so there is no need