linux-kernel - Re: [PATCHv4 27/39] x86-64, mm: proper alignment mappings with hugepages

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Message-Id: <20130625145655.68DCBE0090@blue.fi.intel.com>
Date:	Tue, 25 Jun 2013 17:56:55 +0300 (EEST)
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Dave Hansen <dave@...1.net>
Cc:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Hugh Dickins <hughd@...gle.com>,
	Wu Fengguang <fengguang.wu@...el.com>, Jan Kara <jack@...e.cz>,
	Mel Gorman <mgorman@...e.de>, linux-mm@...ck.org,
	Andi Kleen <ak@...ux.intel.com>,
	Matthew Wilcox <matthew.r.wilcox@...el.com>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Hillf Danton <dhillf@...il.com>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCHv4 27/39] x86-64, mm: proper alignment mappings with
 hugepages

Dave Hansen wrote:
> On 05/11/2013 06:23 PM, Kirill A. Shutemov wrote:
> > +static inline unsigned long mapping_align_mask(struct address_space *mapping)
> > +{
> > +	if (mapping_can_have_hugepages(mapping))
> > +		return PAGE_MASK & ~HPAGE_MASK;
> > +	return get_align_mask();
> > +}
> 
> get_align_mask() appears to be a bit more complicated to me than just a
> plain old mask.  Are you sure you don't need to pick up any of its
> behavior for the mapping_can_have_hugepages() case?

get_align_mask() never returns more strict mask then we do in
mapping_can_have_hugepages() case.

I can modify it this way:

        unsigned long mask = get_align_mask();

        if (mapping_can_have_hugepages(mapping))
                mask &= PAGE_MASK & ~HPAGE_MASK;
        return mask;

But it looks more confusing for me. What do you think?

-- 
 Kirill A. Shutemov
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