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authorYouquan Song <youquan.song@intel.com>2011-12-08 14:34:18 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2011-12-09 07:50:28 -0800
commit58a84aa92723d1ac3e1cc4e3b0ff49291663f7e1 (patch)
treebdfad6b0f38590318da0dee67ff84718b60a8ca5
parentb6999b19120931ede364fa3b685e698a61fed31d (diff)
thp: set compound tail page _count to zero
Commit 70b50f94f1644 ("mm: thp: tail page refcounting fix") keeps all page_tail->_count zero at all times. But the current kernel does not set page_tail->_count to zero if a 1GB page is utilized. So when an IOMMU 1GB page is used by KVM, it wil result in a kernel oops because a tail page's _count does not equal zero. kernel BUG at include/linux/mm.h:386! invalid opcode: 0000 [#1] SMP Call Trace: gup_pud_range+0xb8/0x19d get_user_pages_fast+0xcb/0x192 ? trace_hardirqs_off+0xd/0xf hva_to_pfn+0x119/0x2f2 gfn_to_pfn_memslot+0x2c/0x2e kvm_iommu_map_pages+0xfd/0x1c1 kvm_iommu_map_memslots+0x7c/0xbd kvm_iommu_map_guest+0xaa/0xbf kvm_vm_ioctl_assigned_device+0x2ef/0xa47 kvm_vm_ioctl+0x36c/0x3a2 do_vfs_ioctl+0x49e/0x4e4 sys_ioctl+0x5a/0x7c system_call_fastpath+0x16/0x1b RIP gup_huge_pud+0xf2/0x159 Signed-off-by: Youquan Song <youquan.song@intel.com> Reviewed-by: Andrea Arcangeli <aarcange@redhat.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/hugetlb.c1
-rw-r--r--mm/page_alloc.c2
2 files changed, 2 insertions, 1 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index bb28a5f9db8..73f17c0293c 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -576,6 +576,7 @@ static void prep_compound_gigantic_page(struct page *page, unsigned long order)
__SetPageHead(page);
for (i = 1; i < nr_pages; i++, p = mem_map_next(p, page, i)) {
__SetPageTail(p);
+ set_page_count(p, 0);
p->first_page = page;
}
}
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 9dd443d89d8..850009a7101 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -356,8 +356,8 @@ void prep_compound_page(struct page *page, unsigned long order)
__SetPageHead(page);
for (i = 1; i < nr_pages; i++) {
struct page *p = page + i;
-
__SetPageTail(p);
+ set_page_count(p, 0);
p->first_page = page;
}
}