linux-kernel - Bug in commit aa511ff8218b ("badblocks: switch to the improved badblock handling

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Date: Fri, 22 Dec 2023 10:31:25 -0800
From: Ira Weiny <ira.weiny@...el.com>
To: Coly Li <colyli@...e.de>
CC: Dan Williams <dan.j.williams@...el.com>, Jens Axboe <axboe@...nel.dk>,
	Xiao Ni <xni@...hat.com>, Geliang Tang <geliang.tang@...e.com>, "Hannes
 Reinecke" <hare@...e.de>, NeilBrown <neilb@...e.de>, Vishal L Verma
	<vishal.l.verma@...el.com>, <linux-block@...r.kernel.org>,
	<nvdimm@...ts.linux.dev>, <linux-kernel@...r.kernel.org>
Subject: Bug in commit aa511ff8218b ("badblocks: switch to the improved
 badblock handling

Coly,

Yesterday I noticed that a few of our nvdimm tests were failing.  I bisected
the problem to the following commit.

aa511ff8218b ("badblocks: switch to the improved badblock handling code") 

Reverting this patch fixed our tests.

I've also dug into the code a bit and I believe the algorithm for
badblocks_check() is broken (not yet sure about the other calls).  At the
very least I see the bb->p pointer being indexed with '-1'.  :-(

I did notice that this work was due to a bug report in badblock_set().
Therefore, I'm not sure of that severity of that fix is vs a revert.  But
at this point I'm not seeing an easy fix so I'm in favor of a revert.

Thanks,
Ira