[Question] Is there a race window between swapoff vs synchronous swap_readpage
From: Miaohe Lin
Date: Mon Mar 29 2021 - 09:19:19 EST
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! :)