Re: [PATCH] hugetlb: fix copy_hugetlb_page_range() to handle migration/hwpoisoned entry

[Hugh Dickins <hughd@google.com>]

On Mon, 16 Jun 2014, Naoya Horiguchi wrote:
> On Sun, Jun 15, 2014 at 05:19:29PM -0700, Hugh Dickins wrote:
> > 
> > Hold on, that restriction of hugepage migration was marked for stable
> > 3.12+, whereas this is marked for stable 2.6.36+ (a glance at my old
> > trees suggests 2.6.37+, but you may know better - perhaps hugepage
> > migration got backported to 2.6.36-stable, though hardly seems
> > stable material).
> 
> Sorry, I misinterpreted one thing.
> I thought hugepage migration was merged at 2.6.36 because git-describe
> shows v2.6.36-rc7-73-g290408d4a2 for commit 290408d4a2 "hugetlb: hugepage
> migration core." But actually that's merged at commit f1ebdd60cc, or
> v2.6.36-5792-gf1ebdd60cc73. So this is 2.6.37 stuff.
> 
> Originally hugepage migration was used only for soft offlining in
> mm/memory-failure.c which is available only in x86_64, so we implicitly
> assumed that hugepage migration was restricted to x86_64.
> At 3.12, hugepage migration became available for numa APIs like mbind(),
> which are used for other architectures, so the restriction with
> hugepage_migration_supported() became necessary since then.
> This is the reason why the disablement was marked for 3.12+.
> This patch are helpful before extension in 3.12, so it should be marked 2.6.37+.

That all makes sense to me now: thanks a lot for explaining the history.

Hugh

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