aio/migratepages: make aio migrate pages sane

The arbitrary restriction on page counts offered by the core migrate_page_move_mapping() code results in rather suspicious looking fiddling with page reference counts in the aio_migratepage() operation. To fix this, make migrate_page_move_mapping() take an extra_count parameter that allows aio to tell the code about its own reference count on the page being migrated. While cleaning up aio_migratepage(), make it validate that the old page being passed in is actually what aio_migratepage() expects to prevent misbehaviour in the case of races.

Benjamin LaHaise committed 12 years ago

Commit 8e321fe1 parent 18816863 files · +53 −15Browse files

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include/linux/migrate.h+2−1

@@ -55,7 +55,8 @@ extern int migrate_huge_page_move_mapping(struct address_space *mapping, · 54 unmodified lines
55	55	struct page newpage, struct page page);
56	56	extern int migrate_page_move_mapping(struct address_space *mapping,
57	57	struct page newpage, struct page page,
58		− struct buffer_head *head, enum migrate_mode mode);
	58	+ struct buffer_head *head, enum migrate_mode mode,
	59	+ int extra_count);
59	60	#else
60	61
61	62	static inline void putback_lru_pages(struct list_head *l) {}