diff options
Diffstat (limited to 'include/linux/migrate.h')
| -rw-r--r-- | include/linux/migrate.h | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/include/linux/migrate.h b/include/linux/migrate.h index a4e886d17f87..ce42847ed35f 100644 --- a/include/linux/migrate.h +++ b/include/linux/migrate.h @@ -11,8 +11,18 @@ typedef struct page *new_page_t(struct page *, unsigned long private, int **); * Return values from addresss_space_operations.migratepage(): * - negative errno on page migration failure; * - zero on page migration success; + * + * The balloon page migration introduces this special case where a 'distinct' + * return code is used to flag a successful page migration to unmap_and_move(). + * This approach is necessary because page migration can race against balloon + * deflation procedure, and for such case we could introduce a nasty page leak + * if a successfully migrated balloon page gets released concurrently with + * migration's unmap_and_move() wrap-up steps. */ #define MIGRATEPAGE_SUCCESS 0 +#define MIGRATEPAGE_BALLOON_SUCCESS 1 /* special ret code for balloon page + * sucessful migration case. + */ #ifdef CONFIG_MIGRATION |