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Date:   Mon, 29 May 2023 22:14:51 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Mikulas Patocka <mpatocka@redhat.com>
Cc:     Kent Overstreet <kent.overstreet@linux.dev>,
        linux-bcachefs@vger.kernel.org, dm-devel@redhat.com,
        linux-fsdevel@vger.kernel.org
Subject: Re: fuzzing bcachefs with dm-flakey
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On Mon, May 29, 2023 at 04:59:40PM -0400, Mikulas Patocka wrote:
> Hi
> 
> I improved the dm-flakey device mapper target, so that it can do random 
> corruption of read and write bios - I uploaded it here: 
> https://people.redhat.com/~mpatocka/testcases/bcachefs/dm-flakey.c
> 
> I set up dm-flakey, so that it corrupts 10% of read bios and 10% of write 
> bios with this command:
> dmsetup create flakey --table "0 `blockdev --getsize /dev/ram0` flakey /dev/ram0 0 0 1 4 random_write_corrupt 100000000 random_read_corrupt 100000000"

I'm not suggesting that any of the bugs you've found are invalid, but 10%
seems really high.  Is it reasonable to expect any filesystem to cope
with that level of broken hardware?  Can any of our existing ones cope
with that level of flakiness?  I mean, I've got some pretty shoddy USB
cables, but ...