linux-kernel - [PATCHv6 05/22] thp, mm: introduce mapping_can_have

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Date:	Mon, 23 Sep 2013 15:05:33 +0300
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Andrea Arcangeli <aarcange@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	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 <willy@...ux.intel.com>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Hillf Danton <dhillf@...il.com>, Dave Hansen <dave@...1.net>,
	Ning Qu <quning@...gle.com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCHv6 05/22] thp, mm: introduce mapping_can_have_hugepages() predicate

Returns true if mapping can have huge pages. Just check for __GFP_COMP
in gfp mask of the mapping for now.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 include/linux/pagemap.h | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index e3dea75a07..ad60dcc50e 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -84,6 +84,20 @@ static inline void mapping_set_gfp_mask(struct address_space *m, gfp_t mask)
 				(__force unsigned long)mask;
 }
 
+static inline bool mapping_can_have_hugepages(struct address_space *m)
+{
+	gfp_t gfp_mask = mapping_gfp_mask(m);
+
+	if (!transparent_hugepage_pagecache())
+		return false;
+
+	/*
+	 * It's up to filesystem what gfp mask to use.
+	 * The only part of GFP_TRANSHUGE which matters for us is __GFP_COMP.
+	 */
+	return !!(gfp_mask & __GFP_COMP);
+}
+
 /*
  * The page cache can done in larger chunks than
  * one page, because it allows for more efficient
-- 
1.8.4.rc3

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