diff options
Diffstat (limited to 'mm/migrate.c')
| -rw-r--r-- | mm/migrate.c | 30 |
1 files changed, 24 insertions, 6 deletions
diff --git a/mm/migrate.c b/mm/migrate.c index 4ee4ccacf986..857a987e3690 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -640,15 +640,33 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, rcu_read_lock(); rcu_locked = 1; } + /* - * This is a corner case handling. - * When a new swap-cache is read into, it is linked to LRU - * and treated as swapcache but has no rmap yet. - * Calling try_to_unmap() against a page->mapping==NULL page is - * BUG. So handle it here. + * Corner case handling: + * 1. When a new swap-cache page is read into, it is added to the LRU + * and treated as swapcache but it has no rmap yet. + * Calling try_to_unmap() against a page->mapping==NULL page will + * trigger a BUG. So handle it here. + * 2. An orphaned page (see truncate_complete_page) might have + * fs-private metadata. The page can be picked up due to memory + * offlining. Everywhere else except page reclaim, the page is + * invisible to the vm, so the page can not be migrated. So try to + * free the metadata, so the page can be freed. */ - if (!page->mapping) + if (!page->mapping) { + if (!PageAnon(page) && PagePrivate(page)) { + /* + * Go direct to try_to_free_buffers() here because + * a) that's what try_to_release_page() would do anyway + * b) we may be under rcu_read_lock() here, so we can't + * use GFP_KERNEL which is what try_to_release_page() + * needs to be effective. + */ + try_to_free_buffers(page); + } goto rcu_unlock; + } + /* Establish migration ptes or remove ptes */ try_to_unmap(page, 1); |