mm/z3fold: remove buggy use of stale list for allocation

Currently if z3fold couldn't find an unbuddied page it would first try to
pull a page off the stale list.  But this approach is problematic.  If
init z3fold page fails later, the page should be freed via
free_z3fold_page to clean up the relevant resource instead of using
__free_page directly.  And if page is successfully reused, it will BUG_ON
later in __SetPageMovable because it's already non-lru movable page, i.e.
PAGE_MAPPING_MOVABLE is already set in page->mapping.  In order to fix all
of these issues, we can simply remove the buggy use of stale list for
allocation because can_sleep should always be false and we never really
hit the reusing code path now.

Link: https://lkml.kernel.org/r/20220429064051.61552-4-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/z3fold.c b/mm/z3fold.c
index 5d8c21f2bc59266efb2aed612954d445fb6a8e81..4e6814c5694fa84fd598ad8c81a52ba42dc559ae 100644 (file)
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -1102,28 +1102,7 @@ retry:
                bud = FIRST;
        }
 
-       page = NULL;
-       if (can_sleep) {
-               spin_lock(&pool->stale_lock);
-               zhdr = list_first_entry_or_null(&pool->stale,
-                                               struct z3fold_header, buddy);
-               /*
-                * Before allocating a page, let's see if we can take one from
-                * the stale pages list. cancel_work_sync() can sleep so we
-                * limit this case to the contexts where we can sleep
-                */
-               if (zhdr) {
-                       list_del(&zhdr->buddy);
-                       spin_unlock(&pool->stale_lock);
-                       cancel_work_sync(&zhdr->work);
-                       page = virt_to_page(zhdr);
-               } else {
-                       spin_unlock(&pool->stale_lock);
-               }
-       }
-       if (!page)
-               page = alloc_page(gfp);
-
+       page = alloc_page(gfp);
        if (!page)
                return -ENOMEM;