From: Mel Gorman <mgorman@techsingularity.net>
To: Xie He <xie.he.0141@gmail.com>
Cc: Mel Gorman <mgorman@suse.de>,
jslaby@suse.cz, Neil Brown <neilb@suse.de>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Mike Christie <michaelc@cs.wisc.edu>,
Eric B Munson <emunson@mgebm.net>,
Eric Dumazet <eric.dumazet@gmail.com>,
Sebastian Andrzej Siewior <sebastian@breakpoint.cc>,
Christoph Lameter <cl@linux.com>,
Andrew Morton <akpm@linux-foundation.org>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Linux Kernel Network Developers <netdev@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: Problem in pfmemalloc skb handling in net/core/dev.c
Date: Fri, 9 Apr 2021 09:44:36 +0100 [thread overview]
Message-ID: <20210409084436.GK3697@techsingularity.net> (raw)
In-Reply-To: <CAJht_EPXS3wVoNyaD6edqLPKvDTG2vg4qxiGuWBgWpFsNhB-4g@mail.gmail.com>
On Fri, Apr 09, 2021 at 01:33:24AM -0700, Xie He wrote:
> On Fri, Apr 9, 2021 at 12:30 AM Mel Gorman <mgorman@techsingularity.net> wrote:
> >
> > Under what circumstances do you expect sk_memalloc_socks() to be false
> > and skb_pfmemalloc() to be true that would cause a problem?
>
> For example, if at the time the skb is allocated,
> "sk_memalloc_socks()" was true, then the skb might be allocated as a
> pfmemalloc skb. However, if after this skb is allocated and before
> this skb reaches "__netif_receive_skb", "sk_memalloc_socks()" has
> changed from "true" to "false", then "__netif_receive_skb" will see
> "sk_memalloc_socks()" being false and "skb_pfmemalloc(skb)" being
> true.
>
> This is a problem because this would cause a pfmemalloc skb to be
> delivered to "taps" and protocols that don't support pfmemalloc skbs.
That would imply that the tap was communicating with a swap device to
allocate a pfmemalloc skb which shouldn't happen. Furthermore, it would
require the swap device to be deactivated while pfmemalloc skbs still
existed. Have you encountered this problem?
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2021-04-09 8:44 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-08 18:52 Problem in pfmemalloc skb handling in net/core/dev.c Xie He
2021-04-09 7:30 ` Mel Gorman
2021-04-09 8:33 ` Xie He
2021-04-09 8:44 ` Mel Gorman [this message]
2021-04-09 9:14 ` Xie He
2021-04-09 9:58 ` Mel Gorman
2021-04-09 10:08 ` Xie He
2021-04-09 10:04 ` Eric Dumazet
2021-04-09 10:14 ` Xie He
2021-04-09 11:50 ` Eric Dumazet
2021-04-09 19:12 ` Xie He
2021-04-12 20:40 ` Xie He
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