[PATCH] mm/z3fold.c: Lock z3fold page before __SetPageMovable()

From: Henry Burns <henryburns@google.com>
To: Vitaly Wool <vitalywool@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>
Cc: Vitaly Vul <vitaly.vul@sony.com>,
	Mike Rapoport <rppt@linux.vnet.ibm.com>,
	Xidong Wang <wangxidong_97@163.com>,
	Shakeel Butt <shakeelb@google.com>,
	Jonathan Adams <jwadams@google.com>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Henry Burns <henryburns@google.com>
Subject: [PATCH] mm/z3fold.c: Lock z3fold page before  __SetPageMovable()
Date: Mon,  1 Jul 2019 14:23:03 -0700	[thread overview]
Message-ID: <20190701212303.168581-1-henryburns@google.com> (raw)

__SetPageMovable() expects it's page to be locked, but z3fold.c doesn't
lock the page. Following zsmalloc.c's example we call trylock_page() and
unlock_page(). Also makes z3fold_page_migrate() assert that newpage is
passed in locked, as documentation.

Signed-off-by: Henry Burns <henryburns@google.com>
---
 mm/z3fold.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/z3fold.c b/mm/z3fold.c
index e174d1549734..5bc404dbbb4a 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -918,7 +918,9 @@ static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
 		set_bit(PAGE_HEADLESS, &page->private);
 		goto headless;
 	}
+	WARN_ON(!trylock_page(page));
 	__SetPageMovable(page, pool->inode->i_mapping);
+	unlock_page(page);
 	z3fold_page_lock(zhdr);
 
 found:
@@ -1325,6 +1327,7 @@ static int z3fold_page_migrate(struct address_space *mapping, struct page *newpa
 
 	VM_BUG_ON_PAGE(!PageMovable(page), page);
 	VM_BUG_ON_PAGE(!PageIsolated(page), page);
+	VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
 
 	zhdr = page_address(page);
 	pool = zhdr_to_pool(zhdr);
-- 
2.22.0.410.gd8fdbe21b5-goog

