netdev - Re: [PATCH 12/17] netvm: Propagate page->pfmemalloc from skb_alloc

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Message-Id: <20120517.161304.1765970628771192598.davem@davemloft.net>
Date:	Thu, 17 May 2012 16:13:04 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	mgorman@...e.de
Cc:	akpm@...ux-foundation.org, linux-mm@...ck.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	neilb@...e.de, a.p.zijlstra@...llo.nl, michaelc@...wisc.edu,
	emunson@...bm.net
Subject: Re: [PATCH 12/17] netvm: Propagate page->pfmemalloc from
 skb_alloc_page to skb

From: Mel Gorman <mgorman@...e.de>
Date: Thu, 17 May 2012 15:50:26 +0100

> The skb->pfmemalloc flag gets set to true iff during the slab
> allocation of data in __alloc_skb that the the PFMEMALLOC reserves
> were used. If page splitting is used, it is possible that pages will
> be allocated from the PFMEMALLOC reserve without propagating this
> information to the skb. This patch propagates page->pfmemalloc from
> pages allocated for fragments to the skb.
> 
> It works by reintroducing and expanding the skb_alloc_page() API
> to take an skb. If the page was allocated from pfmemalloc reserves,
> it is automatically copied. If the driver allocates the page before
> the skb, it should call skb_propagate_pfmemalloc() after the skb is
> allocated to ensure the flag is copied properly.
> 
> Failure to do so is not critical. The resulting driver may perform
> slower if it is used for swap-over-NBD or swap-over-NFS but it should
> not result in failure.
> 
> [davem@...emloft.net: API rename and consistency]
> Signed-off-by: Mel Gorman <mgorman@...e.de>

Acked-by: David S. Miller <davem@...emloft.net>
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