linux-kernel - Re: swapon/913 is trying to acquire lock at zcomp_stream_get+0x5/0x90 [zram] but task is already holding lock at zs_map

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Message-ID: <CABXGCsOoY+J4kfX22c=KhGui_f=M4t72xXEEkUPM3szOd0WG+A@mail.gmail.com>
Date:   Fri, 16 Oct 2020 19:00:29 +0500
From:   Mikhail Gavrilov <mikhail.v.gavrilov@...il.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        linux-block@...r.kernel.org,
        Mike Galbraith <umgwanakikbuti@...il.com>, minchan@...nel.org,
        ngupta@...are.org, sergey.senozhatsky.work@...il.com,
        bigeasy@...utronix.de
Subject: Re: swapon/913 is trying to acquire lock at zcomp_stream_get+0x5/0x90
 [zram] but task is already holding lock at zs_map_object+0x7a/0x2e0

On Fri, 16 Oct 2020 at 17:40, Peter Zijlstra <peterz@...radead.org> wrote:
>
>
> Joy... __zram_bvec_write() and __zram_bvec_read() take these locks in
> opposite order.
>
> Does something like the (_completely_) untested below cure things?

Excellent! This patch (_completely_) cured all other warnings which
were present in the log.
dmesg before patch: https://pastebin.com/tZY3npHG
dmesg after patch: https://pastebin.com/iD7ZL1mb

Thanks!

--
Best Regards,
Mike Gavrilov.