linux-kernel - Re: qemu-arm: zram: mkfs.ext4 : Unable to handle kernel NULL pointer dereference at virtual address 00000140

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Message-ID: <YqHTUdeZ8H0Lnf8E@google.com>
Date:   Thu, 9 Jun 2022 20:02:41 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     Minchan Kim <minchan@...nel.org>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Naresh Kamboju <naresh.kamboju@...aro.org>,
        open list <linux-kernel@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        linux-block <linux-block@...r.kernel.org>,
        regressions@...ts.linux.dev, Jens Axboe <axboe@...nel.dk>,
        Nitin Gupta <ngupta@...are.org>
Subject: Re: qemu-arm: zram: mkfs.ext4 : Unable to handle kernel NULL pointer
 dereference at virtual address 00000140

On (22/06/08 13:45), Minchan Kim wrote:
> 
> I am trying to understand the problem. AFAIK, the mapping_area was
> static allocation per cpu so in zs_cpu_down, we never free the
> mapping_area itself. Then, why do we need to reinitialize the local
> lock again?

Well... Something zero-s out that memory. NULL deref in strcmp() in
lockdep points at NULL ->name. So I'm merely testing my theories here.
If it's not area lock then it's pool->migrate_lock?