netdev - Re: [PATCHv2] net: suppress warnings on dev_alloc

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Message-ID: <1463679590.18194.207.camel@edumazet-glaptop3.roam.corp.google.com>
Date:	Thu, 19 May 2016 10:39:50 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Neil Horman <nhorman@...driver.com>
Cc:	netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
	Alexander Duyck <alexander.duyck@...il.com>
Subject: Re: [PATCHv2] net: suppress warnings on dev_alloc_skb

On Thu, 2016-05-19 at 13:34 -0400, Neil Horman wrote:
> On Thu, May 19, 2016 at 08:48:56AM -0700, Eric Dumazet wrote:
> > On Thu, 2016-05-19 at 11:30 -0400, Neil Horman wrote:
> > > Noticed an allocation failure in a network driver the other day on a 32 bit
> > > system:
> > 
> > Presumably driver could fall back to HIGH memory allocation for the page
> > frag.
> > 
> Is that safe on a 32 bit system?
> Neil

This should be.

Unless a bug somewhere was added, since most dev are using 64bit kernels
these days.

All frag consumers use the appropriate kmap_atomic()/kunmap_atomic()
pairs before copying data from a page frag. Meaning the page can be in
HIGH memory.