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Message-ID: <364d7ce9-ccb7-fa04-7067-44a96be87060@huawei.com>
Date: Mon, 29 Mar 2021 21:18:20 +0800
From: Miaohe Lin <linmiaohe@...wei.com>
To: Linux-MM <linux-mm@...ck.org>,
linux-kernel <linux-kernel@...r.kernel.org>
CC: Andrew Morton <akpm@...ux-foundation.org>,
Matthew Wilcox <willy@...radead.org>,
Yu Zhao <yuzhao@...gle.com>,
Shakeel Butt <shakeelb@...gle.com>,
Alex Shi <alex.shi@...ux.alibaba.com>,
Huang Ying <ying.huang@...el.com>
Subject: [Question] Is there a race window between swapoff vs synchronous
swap_readpage
Hi all,
I am investigating the swap code, and I found the below possible race window:
CPU 1 CPU 2
----- -----
do_swap_page
skip swapcache case (synchronous swap_readpage)
alloc_page_vma
swapoff
release swap_file, bdev, or ...
swap_readpage
check sis->flags is ok
access swap_file, bdev or ...[oops!]
si->flags = 0
The swapcache case is ok because swapoff will wait on the page_lock of swapcache page.
Is this will really happen or Am I miss something ?
Any reply would be really grateful. Thanks! :)
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