From: Andrew Morton <akpm@linux-foundation.org>
To: David Rientjes <rientjes@google.com>
Cc: Mel Gorman <mgorman@suse.de>, Michal Hocko <mhocko@suse.cz>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [patch] mm, page_alloc: make __GFP_NOFAIL really not fail
Date: Mon, 9 Dec 2013 15:22:02 -0800 [thread overview]
Message-ID: <20131209152202.df3d4051d7dc61ada7c420a9@linux-foundation.org> (raw)
In-Reply-To: <alpine.DEB.2.02.1312091355360.11026@chino.kir.corp.google.com>
On Mon, 9 Dec 2013 13:56:37 -0800 (PST) David Rientjes <rientjes@google.com> wrote:
> __GFP_NOFAIL specifies that the page allocator cannot fail to return
> memory. Allocators that call it may not even check for NULL upon
> returning.
>
> It turns out GFP_NOWAIT | __GFP_NOFAIL or GFP_ATOMIC | __GFP_NOFAIL can
> actually return NULL. More interestingly, processes that are doing
> direct reclaim and have PF_MEMALLOC set may also return NULL for any
> __GFP_NOFAIL allocation.
__GFP_NOFAIL is a nasty thing and making it pretend to work even better
is heading in the wrong direction, surely? It would be saner to just
disallow these even-sillier combinations. Can we fix up the current
callers then stick a WARN_ON() in there?
> This patch fixes it so that the page allocator never actually returns
> NULL as expected for __GFP_NOFAIL. It turns out that no code actually
> does anything as crazy as GFP_ATOMIC | __GFP_NOFAIL currently, so this
> is more for correctness than a bug fix for that issue.
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next prev parent reply other threads:[~2013-12-09 23:22 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-09 21:56 David Rientjes
2013-12-09 23:22 ` Andrew Morton [this message]
2013-12-10 23:20 ` David Rientjes
2013-12-10 23:39 ` Andrew Morton
2013-12-11 0:11 ` David Rientjes
2013-12-12 1:07 ` Dave Chinner
2013-12-11 0:19 ` [patch alternative] mm, page_alloc: warn for non-blockable __GFP_NOFAIL allocation failure David Rientjes
2013-12-11 0:26 ` [patch] checkpatch: add warning of future __GFP_NOFAIL use David Rientjes
2013-12-11 1:35 ` Joe Perches
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