Re: [PATCH 04/11] unpaged: unifdefed PageCompound

From: David S. Miller
Date: Thu Nov 17 2005 - 18:43:49 EST

From: Hugh Dickins <hugh@xxxxxxxxxxx>
Date: Thu, 17 Nov 2005 19:32:40 +0000 (GMT)

> It looks like snd_xxx is not the only nopage to be using PageReserved as
> a way of holding a high-order page together: which no longer works, but
> is masked by our failure to free from VM_RESERVED areas. We cannot fix
> that bug without first substituting another way to hold the high-order
> page together, while farming out the 0-order pages from within it.
> That's just what PageCompound is designed for, but it's been kept under
> CONFIG_HUGETLB_PAGE. Remove the #ifdefs: which saves some space (out-
> of-line put_page), doesn't slow down what most needs to be fast (already
> using hugetlb), and unifies the way we handle high-order pages.
> Signed-off-by: Hugh Dickins <hugh@xxxxxxxxxxx>

I think this is a good change regardless of the VM_RESERVED issues.

I've been wanting to use this facility in some sparc64 bits in
the past, for example. But since it was HUGETLB guarded that
wasn't possible.
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