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authorYouquan Song <youquan.song@intel.com>2011-12-08 14:34:16 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2011-12-09 07:50:28 -0800
commitb6999b19120931ede364fa3b685e698a61fed31d (patch)
treecadfc55786baf45ae05b02523d61e476eaf18154
parent09dc3cf93f7d16fdd37a0ad8486faebb5e2769ec (diff)
downloadlinux-stericsson-b6999b19120931ede364fa3b685e698a61fed31d.tar.gz
thp: add compound tail page _mapcount when mapped
With the 3.2-rc kernel, IOMMU 2M pages in KVM works. But when I tried to use IOMMU 1GB pages in KVM, I encountered an oops and the 1GB page failed to be used. The root cause is that 1GB page allocation calls gup_huge_pud() while 2M page calls gup_huge_pmd. If compound pages are used and the page is a tail page, gup_huge_pmd() increases _mapcount to record tail page are mapped while gup_huge_pud does not do that. So when the mapped page is relesed, it will result in kernel oops because the page is not marked mapped. This patch add tail process for compound page in 1GB huge page which keeps the same process as 2M page. Reproduce like: 1. Add grub boot option: hugepagesz=1G hugepages=8 2. mount -t hugetlbfs -o pagesize=1G hugetlbfs /dev/hugepages 3. qemu-kvm -m 2048 -hda os-kvm.img -cpu kvm64 -smp 4 -mem-path /dev/hugepages -net none -device pci-assign,host=07:00.1 kernel BUG at mm/swap.c:114! invalid opcode: 0000 [#1] SMP Call Trace: put_page+0x15/0x37 kvm_release_pfn_clean+0x31/0x36 kvm_iommu_put_pages+0x94/0xb1 kvm_iommu_unmap_memslots+0x80/0xb6 kvm_assign_device+0xba/0x117 kvm_vm_ioctl_assigned_device+0x301/0xa47 kvm_vm_ioctl+0x36c/0x3a2 do_vfs_ioctl+0x49e/0x4e4 sys_ioctl+0x5a/0x7c system_call_fastpath+0x16/0x1b RIP put_compound_page+0xd4/0x168 Signed-off-by: Youquan Song <youquan.song@intel.com> Reviewed-by: Andrea Arcangeli <aarcange@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> 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--arch/x86/mm/gup.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c
index ea305856151c..dd74e46828c0 100644
--- a/arch/x86/mm/gup.c
+++ b/arch/x86/mm/gup.c
@@ -201,6 +201,8 @@ static noinline int gup_huge_pud(pud_t pud, unsigned long addr,
do {
VM_BUG_ON(compound_head(page) != head);
pages[*nr] = page;
+ if (PageTail(page))
+ get_huge_page_tail(page);
(*nr)++;
page++;
refs++;