linux-kernel - Re: kmemleak report after 9082e87bfbf8 ("block: remove struct bio

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Date:	Mon, 6 Jun 2016 18:35:56 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	Christoph Hellwig <hch@....de>
Cc:	Shaun Tancheff <shaun.tancheff@...gate.com>,
	linux-block@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	Jens Axboe <axboe@...com>, Larry.Finger@...inger.net,
	bart.vanassche@...disk.com, drysdale@...gle.com
Subject: Re: kmemleak report after 9082e87bfbf8 ("block: remove struct
 bio_batch")

On Mon, Jun 06, 2016 at 07:27:18PM +0200, Christoph Hellwig wrote:
> On Mon, Jun 06, 2016 at 12:09:49PM -0500, Shaun Tancheff wrote:
> > I'm pretty sure it is missing a bio_put() after submit_bio_wait().
> > 
> > Please excuse the hack-y patch but I think you need to do something
> > like this ...
> > (Note tabs eaten by gmail).
> 
> Yeah, that makes sense - oddly enough submit_bio_wait doesn't do a
> bio_put. Still not sure why I don't see the leaks after repeated
> mkfs.xfs runs, though.

You can force more kmemleak scans via:

  echo scan > /sys/kernel/debug/kmemleak

In my case, the leaks were reported for ext4 and appeared during boot,
no need for mkfs. But kmemleak favours false negatives more than
positives (otherwise it would be pretty unusable), so you don't always
hit them.

-- 
Catalin