linux-kernel - [PATCH] mm/z3fold.c: Lock z3fold page before _

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Date:   Mon,  1 Jul 2019 14:23:03 -0700
From:   Henry Burns <henryburns@...gle.com>
To:     Vitaly Wool <vitalywool@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Vitaly Vul <vitaly.vul@...y.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Xidong Wang <wangxidong_97@....com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Jonathan Adams <jwadams@...gle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Henry Burns <henryburns@...gle.com>
Subject: [PATCH] mm/z3fold.c: Lock z3fold page before  __SetPageMovable()

__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@...gle.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