linux-kernel - Re: [PATCH] io_uring: avoid page allocation warnings

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Date:   Wed, 1 May 2019 16:55:51 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     Matthew Wilcox <willy@...radead.org>, linux-kernel@...r.kernel.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org
Subject: Re: [PATCH] io_uring: avoid page allocation warnings

On Wed, May 01, 2019 at 09:29:25AM -0600, Jens Axboe wrote:
> On 5/1/19 9:09 AM, Mark Rutland wrote:
> > I've manually minimized that to C below. AFAICT, that hits a leak, which
> > is what's triggering the OOM after the program is run a number of times
> > with the previously posted kvmalloc patch.
> > 
> > Per /proc/meminfo, that memory isn't accounted anywhere.
> > 
> >> Patch looks fine to me. Note
> >> that buffer registration is under the protection of RLIMIT_MEMLOCK.
> >> That's usually very limited for non-root, as root you can of course
> >> consume as much as you want and OOM the system.
> > 
> > Sure.
> > 
> > As above, it looks like there's a leak, regardless.
> 
> The leak is that we're not releasing imu->bvec in case of error. I fixed
> a missing kfree -> kvfree as well in your patch, with this rolled up
> version it works for me.

That works for me too.

I'll fold that into v2, and send that out momentarily.

Thanks,
Mark.