+ mm-hugetlb-fix-gigantic-page-initialization-allocation.patch added to -mm tree

+ mm-hugetlb-fix-gigantic-page-initialization-allocation.patch added to -mm tree

[akpm]

The patch titled
     Subject: mm/hugetlb: fix gigantic page initialization/allocation
has been added to the -mm tree.  Its filename is
     mm-hugetlb-fix-gigantic-page-initialization-allocation.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/mm-hugetlb-fix-gigantic-page-initialization-allocation.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/mm-hugetlb-fix-gigantic-page-initialization-allocation.patch

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------------------------------------------------------
From: Mike Kravetz <mike.kravetz@oracle.com>
Subject: mm/hugetlb: fix gigantic page initialization/allocation

Attempting to preallocate 1G gigantic huge pages at boot time with
"hugepagesz=1G hugepages=1" on the kernel command line will prevent
booting with the following:

kernel BUG at mm/hugetlb.c:1218!

When mapcount accounting was reworked, the setting of
compound_mapcount_ptr in prep_compound_gigantic_page was overlooked.  As a
result, the validation of mapcount in free_huge_page fails.

The "BUG_ON" checks in free_huge_page were also changed to "VM_BUG_ON_PAGE"
to assist with debugging.

Fixes: 53f9263baba69 ("mm: rework mapcount accounting to enable 4k mapping of THPs")
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Suggested-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/hugetlb.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff -puN mm/hugetlb.c~mm-hugetlb-fix-gigantic-page-initialization-allocation mm/hugetlb.c
--- a/mm/hugetlb.c~mm-hugetlb-fix-gigantic-page-initialization-allocation
+++ a/mm/hugetlb.c
@@ -1214,8 +1214,8 @@ void free_huge_page(struct page *page)
 
 	set_page_private(page, 0);
 	page->mapping = NULL;
-	BUG_ON(page_count(page));
-	BUG_ON(page_mapcount(page));
+	VM_BUG_ON_PAGE(page_count(page), page);
+	VM_BUG_ON_PAGE(page_mapcount(page), page);
 	restore_reserve = PagePrivate(page);
 	ClearPagePrivate(page);
 
@@ -1286,6 +1286,7 @@ static void prep_compound_gigantic_page(
 		set_page_count(p, 0);
 		set_compound_head(p, page);
 	}
+	atomic_set(compound_mapcount_ptr(page), -1);
 }
 
 /*
_

Patches currently in -mm which might be from mike.kravetz@oracle.com are

mm-hugetlb-fix-gigantic-page-initialization-allocation.patch