Commit df6f0f1d authored Apr 29, 2022 by Miaohe Lin Committed by Andrew Morton May 27, 2022

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>

parent 7c61c35b

mm/z3fold.c

+1 −22

Original line number	Diff line number	Diff line
		@@ -1102,28 +1102,7 @@ static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
		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);

		if (!page)
		return -ENOMEM;