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From: Tejun Heo <tj@kernel.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	netdev@vger.kernel.org, syzkaller@googlegroups.com,
	"David S. Miller" <davem@davemloft.net>,
	Alexei Starovoitov <ast@kernel.org>,
	Christoph Lameter <cl@linux.com>
Subject: Re: EBPF-triggered WARNING at mm/percpu.c:1361 in v4-14-rc2
Date: Thu, 28 Sep 2017 07:53:02 -0700	[thread overview]
Message-ID: <20170928145302.GE15129@devbig577.frc2.facebook.com> (raw)
In-Reply-To: <20170928144538.GA32487@leverpostej>

Hello,

On Thu, Sep 28, 2017 at 03:45:38PM +0100, Mark Rutland wrote:
> > Perhaps the pr_warn() should be ratelimited; or could there be an
> > option where we only return NULL, not triggering a warn at all (which
> > would likely be what callers might do anyway when checking against
> > PCPU_MIN_UNIT_SIZE and then bailing out)?
> 
> Those both make sense to me; checking __GFP_NOWARN should be easy
> enough.

That also makes sense.

> Just to check, do you think that dev_map_alloc() should explicitly test
> the size against PCPU_MIN_UNIT_SIZE, prior to calling pcpu_alloc()?

But let's please not do this.

Thanks.

-- 
tejun

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WARNING: multiple messages have this Message-ID (diff)
From: Tejun Heo <tj@kernel.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	netdev@vger.kernel.org, syzkaller@googlegroups.com,
	"David S. Miller" <davem@davemloft.net>,
	Alexei Starovoitov <ast@kernel.org>,
	Christoph Lameter <cl@linux.com>
Subject: Re: EBPF-triggered WARNING at mm/percpu.c:1361 in v4-14-rc2
Date: Thu, 28 Sep 2017 07:53:02 -0700	[thread overview]
Message-ID: <20170928145302.GE15129@devbig577.frc2.facebook.com> (raw)
In-Reply-To: <20170928144538.GA32487@leverpostej>

Hello,

On Thu, Sep 28, 2017 at 03:45:38PM +0100, Mark Rutland wrote:
> > Perhaps the pr_warn() should be ratelimited; or could there be an
> > option where we only return NULL, not triggering a warn at all (which
> > would likely be what callers might do anyway when checking against
> > PCPU_MIN_UNIT_SIZE and then bailing out)?
> 
> Those both make sense to me; checking __GFP_NOWARN should be easy
> enough.

That also makes sense.

> Just to check, do you think that dev_map_alloc() should explicitly test
> the size against PCPU_MIN_UNIT_SIZE, prior to calling pcpu_alloc()?

But let's please not do this.

Thanks.

-- 
tejun

  reply	other threads:[~2017-09-28 14:53 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-09-28 11:27 EBPF-triggered WARNING at mm/percpu.c:1361 in v4-14-rc2 Mark Rutland
2017-09-28 11:27 ` Mark Rutland
2017-09-28 14:37 ` Daniel Borkmann
2017-09-28 14:37   ` Daniel Borkmann
2017-09-28 14:45   ` Mark Rutland
2017-09-28 14:45     ` Mark Rutland
2017-09-28 14:53     ` Tejun Heo [this message]
2017-09-28 14:53       ` Tejun Heo
2017-09-28 15:00     ` Daniel Borkmann
2017-09-28 15:00       ` Daniel Borkmann
2017-09-28 14:52 ` Tejun Heo
2017-09-28 14:52   ` Tejun Heo

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