linux-kernel - Re: [PATCH 2/6] mm: mark all calls into the vmalloc subsystem as potentially sleeping

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Date:   Tue, 18 Oct 2016 12:38:37 +0200
From:   Christoph Hellwig <hch@....de>
To:     Chris Wilson <chris@...is-wilson.co.uk>
Cc:     Christoph Hellwig <hch@....de>, akpm@...ux-foundation.org,
        joelaf@...gle.com, jszhang@...vell.com, joaodias@...gle.com,
        linux-mm@...ck.org, linux-rt-users@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/6] mm: mark all calls into the vmalloc subsystem as
        potentially sleeping

On Tue, Oct 18, 2016 at 11:33:59AM +0100, Chris Wilson wrote:
> On Tue, Oct 18, 2016 at 08:56:07AM +0200, Christoph Hellwig wrote:
> > This is how everyone seems to already use them, but let's make that
> > explicit.
> 
> mm/page_alloc.c: alloc_large_system_hash() is perhaps the exception to
> the rule.

While alloc_large_system_hash passes GFP_ATOMIC it still is called
from context where it can sleep - I think it just abuses GFP_ATOMIC
so that it gets an "early" failure.  For which GFP_ATOMIC isn't
exactly a good choice as it dips into additional reserves, GFP_NOWAIT
would have probably been a better choice.