linux-kernel - Re: [PATCH] mm/hugetlb: Get rid of NODEMASK

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Message-Id: <20190402130153.338e59c6cfda1ed3ec882517@linux-foundation.org>
Date:   Tue, 2 Apr 2019 13:01:53 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Oscar Salvador <osalvador@...e.de>
Cc:     mike.kravetz@...cle.com, n-horiguchi@...jp.nec.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/hugetlb: Get rid of NODEMASK_ALLOC

On Tue,  2 Apr 2019 15:34:15 +0200 Oscar Salvador <osalvador@...e.de> wrote:

> NODEMASK_ALLOC is used to allocate a nodemask bitmap, ant it does it by
> first determining whether it should be allocated in the stack or dinamically
> depending on NODES_SHIFT.
> Right now, it goes the dynamic path whenever the nodemask_t is above 32
> bytes.
> 
> Although we could bump it to a reasonable value, the largest a nodemask_t
> can get is 128 bytes, so since __nr_hugepages_store_common is called from
> a rather shore stack we can just get rid of the NODEMASK_ALLOC call here.
> 
> This reduces some code churn and complexity.

It took a bit of sleuthing to figure out that this patch applies to
Mike's "hugetlbfs: fix potential over/underflow setting node specific
nr_hugepages".  Should they be folded together?  I'm thinking not.

(Also, should "hugetlbfs: fix potential over/underflow setting node
specific nr_hugepages" have been -stableified?  I also think not, but I
bet it happens anyway).