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From:   Ivan Babrou <ivan@cloudflare.com>
Date:   Mon, 14 Mar 2022 21:54:06 -0700
Message-ID: <CABWYdi1zbc5pN28AKA31cGkD---7ODAOKQ7Tp=d=jhYScHDNFw@mail.gmail.com>
Subject: Re: zram corruption due to uninitialized do_swap_page fault
To:     Hillf Danton <hdanton@sina.com>
Cc:     Minchan Kim <minchan@kernel.org>, Linux MM <linux-mm@kvack.org>,
        linux-kernel <linux-kernel@vger.kernel.org>
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On Mon, Mar 14, 2022 at 9:34 PM Hillf Danton <hdanton@sina.com> wrote:
> Can you test if the race comes from the diff below wrt zram_free_page?
>
> Hillf
>
> --- upstream/mm/page_io.c
> +++ b/mm/page_io.c
> @@ -392,11 +392,6 @@ int swap_readpage(struct page *page, boo
>         if (sis->flags & SWP_SYNCHRONOUS_IO) {
>                 ret = bdev_read_page(sis->bdev, swap_page_sector(page), page);
>                 if (!ret) {
> -                       if (trylock_page(page)) {
> -                               swap_slot_free_notify(page);
> -                               unlock_page(page);
> -                       }
> -
>                         count_vm_event(PSWPIN);
>                         goto out;
>                 }

I tried it without the previous patch (the one commenting out
swap_slot_free_notify in end_swap_bio_read) and it still fails.