On Sat, Aug 30, 2014 at 08:41:13PM +0400, Konstantin Khlebnikov wrote: > From: Konstantin Khlebnikov <[email protected]> > > Proper testing shows yet another problem in balloon migration: it works only > once for each page. balloon_page_movable() check page flags and page_count. > In __unmap_and_move page is locked, reference counter is elevated, so > balloon_page_movable() _always_ fails here. As result in __unmap_and_move() > migration goes to the normal migration path. > > Balloon ->migratepage() is so special, it returns MIGRATEPAGE_BALLOON_SUCCESS > instead of MIGRATEPAGE_SUCCESS. After that in move_to_new_page() successfully > migrated page got NULL into its mapping pointer and loses connectivity with > balloon and ability for further migration. > > It's safe to use __is_movable_balloon_page here: page is isolated and pinned. > > Signed-off-by: Konstantin Khlebnikov <[email protected]> > Cc: stable <[email protected]> # v3.8 > --- > include/linux/balloon_compaction.h | 5 +++++ > mm/migrate.c | 2 +- > 2 files changed, 6 insertions(+), 1 deletion(-) > > diff --git a/include/linux/balloon_compaction.h > b/include/linux/balloon_compaction.h > index 53d482e..284fc1d 100644 > --- a/include/linux/balloon_compaction.h > +++ b/include/linux/balloon_compaction.h > @@ -258,6 +258,11 @@ static inline void balloon_page_delete(struct page *page) > list_del(&page->lru); > } > > +static inline bool __is_movable_balloon_page(struct page *page) > +{ > + return false; > +} > + > static inline bool balloon_page_movable(struct page *page) > { > return false; > diff --git a/mm/migrate.c b/mm/migrate.c > index 905b1aa..57c94f9 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -873,7 +873,7 @@ static int __unmap_and_move(struct page *page, struct > page *newpage, > } > } > > - if (unlikely(balloon_page_movable(page))) { > + if (unlikely(__is_movable_balloon_page(page))) { > /* > * A ballooned page does not need any special attention from > * physical to virtual reverse mapping procedures. > Acked-by: Rafael Aquini <[email protected]>
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