linux-kernel - [PATCH] mm,numa,THP: initialize hstate for THP page size

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Message-ID: <20131218170314.1e57bea7@cuia.bos.redhat.com>
Date:	Wed, 18 Dec 2013 17:03:14 -0500
From:	Rik van Riel <riel@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	Chao Yang <chayang@...hat.com>, linux-mm@...ck.org,
	akpm@...ux-foundation.org, aarcange@...hat.com, mgorman@...e.de,
	Veaceslav Falico <vfalico@...hat.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	David Rientjes <rientjes@...gle.com>,
	Michel Lespinasse <walken@...gle.com>,
	Michal Hocko <mhocko@...e.cz>
Subject: [PATCH] mm,numa,THP: initialize hstate for THP page size

When hugetlbfs is started with a non-default page size, it is
possible that no hstate is initialized for the page sized used
by transparent huge pages.

This causes copy_huge_page to crash on a null pointer. Make
sure we always have an hpage initialized for the page sized
used by THP.

Signed-off-by: Rik van Riel <riel@...hat.com>
Reported-by: Chao Yang <chayang@...hat.com>
---
 mm/huge_memory.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 5749bcf..583e9d3 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -624,6 +624,13 @@ static int __init hugepage_init(void)
 		return -EINVAL;
 	}
 
+	/*
+	 * Make sure an hstate is initialized for our page size,
+	 * even if hugetlbfs is using a non-default page size.
+	 */
+	if (!size_to_hstate(PMD_PAGE_SIZE))
+		hugetlb_add_hstate(HUGETLB_PAGE_ORDER);
+
 	err = hugepage_init_sysfs(&hugepage_kobj);
 	if (err)
 		return err;


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