kernel.git/mm/balloon_compaction.c, branch linux-3.12.y

mm/balloon_compaction: fix deflation when compaction is disabled

2016-05-13T13:09:38Z

commit 4d88e6f7d5ffc84e6094a47925870f4a130555c2 upstream. If CONFIG_BALLOON_COMPACTION=n balloon_page_insert() does not link pages with balloon and doesn't set PagePrivate flag, as a result balloon_page_dequeue() cannot get any pages because it thinks that all of them are isolated. Without balloon compaction nobody can isolate ballooned pages. It's safe to remove this check. Fixes: d6d86c0a7f8d ("mm/balloon_compaction: redesign ballooned pages management"). Signed-off-by: Konstantin Khlebnikov Reported-by: Matt Mullins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Cc: Gavin Guo Signed-off-by: Jiri Slaby

mm/balloon_compaction: redesign ballooned pages management

2016-05-13T13:09:25Z

commit d6d86c0a7f8ddc5b38cf089222cb1d9540762dc2 upstream. Sasha Levin reported KASAN splash inside isolate_migratepages_range(). Problem is in the function __is_movable_balloon_page() which tests AS_BALLOON_MAP in page->mapping->flags. This function has no protection against anonymous pages. As result it tried to check address space flags inside struct anon_vma. Further investigation shows more problems in current implementation: * Special branch in __unmap_and_move() never works: balloon_page_movable() checks page flags and page_count. In __unmap_and_move() page is locked, reference counter is elevated, thus balloon_page_movable() always fails. As a result execution goes to the normal migration path. virtballoon_migratepage() returns MIGRATEPAGE_BALLOON_SUCCESS instead of MIGRATEPAGE_SUCCESS, move_to_new_page() thinks this is an error code and assigns newpage->mapping to NULL. Newly migrated page lose connectivity with balloon an all ability for further migration. * lru_lock erroneously required in isolate_migratepages_range() for isolation ballooned page. This function releases lru_lock periodically, this makes migration mostly impossible for some pages. * balloon_page_dequeue have a tight race with balloon_page_isolate: balloon_page_isolate could be executed in parallel with dequeue between picking page from list and locking page_lock. Race is rare because they use trylock_page() for locking. This patch fixes all of them. Instead of fake mapping with special flag this patch uses special state of page->_mapcount: PAGE_BALLOON_MAPCOUNT_VALUE = -256. Buddy allocator uses PAGE_BUDDY_MAPCOUNT_VALUE = -128 for similar purpose. Storing mark directly in struct page makes everything safer and easier. PagePrivate is used to mark pages present in page list (i.e. not isolated, like PageLRU for normal pages). It replaces special rules for reference counter and makes balloon migration similar to migration of normal pages. This flag is protected by page_lock together with link to the balloon device. [js] backport to 3.12. MIGRATEPAGE_BALLOON_SUCCESS had to be removed from one more place. VM_BUG_ON_PAGE does not exist in 3.12 yet, use plain VM_BUG_ON. Signed-off-by: Konstantin Khlebnikov Reported-by: Sasha Levin Link: http://lkml.kernel.org/p/53E6CEAA.9020105@oracle.com Cc: Rafael Aquini Cc: Andrey Ryabinin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Cc: Gavin Guo Signed-off-by: Jiri Slaby

mm: introduce a common interface for balloon pages mobility

2012-12-12T01:22:26Z

Memory fragmentation introduced by ballooning might reduce significantly the number of 2MB contiguous memory blocks that can be used within a guest, thus imposing performance penalties associated with the reduced number of transparent huge pages that could be used by the guest workload. This patch introduces a common interface to help a balloon driver on making its page set movable to compaction, and thus allowing the system to better leverage the compation efforts on memory defragmentation. [akpm@linux-foundation.org: use PAGE_FLAGS_CHECK_AT_PREP, s/__balloon_page_flags/page_flags_cleared/, small cleanups] [rientjes@google.com: allow balloon compaction for any system with memory compaction enabled, which is the defconfig] Signed-off-by: Rafael Aquini Acked-by: Mel Gorman Cc: Rusty Russell Cc: "Michael S. Tsirkin" Cc: Rik van Riel Cc: Andi Kleen Cc: Konrad Rzeszutek Wilk Cc: Minchan Kim Signed-off-by: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds