| From foo@baz Sun May 27 17:33:38 CEST 2018 |
| From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> |
| Date: Wed, 31 Jan 2018 16:17:43 -0800 |
| Subject: asm-generic: provide generic_pmdp_establish() |
| |
| From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> |
| |
| [ Upstream commit c58f0bb77ed8bf93dfdde762b01cb67eebbdfc29 ] |
| |
| Patch series "Do not lose dirty bit on THP pages", v4. |
| |
| Vlastimil noted that pmdp_invalidate() is not atomic and we can lose |
| dirty and access bits if CPU sets them after pmdp dereference, but |
| before set_pmd_at(). |
| |
| The bug can lead to data loss, but the race window is tiny and I haven't |
| seen any reports that suggested that it happens in reality. So I don't |
| think it worth sending it to stable. |
| |
| Unfortunately, there's no way to address the issue in a generic way. We |
| need to fix all architectures that support THP one-by-one. |
| |
| All architectures that have THP supported have to provide atomic |
| pmdp_invalidate() that returns previous value. |
| |
| If generic implementation of pmdp_invalidate() is used, architecture |
| needs to provide atomic pmdp_estabish(). |
| |
| pmdp_estabish() is not used out-side generic implementation of |
| pmdp_invalidate() so far, but I think this can change in the future. |
| |
| This patch (of 12): |
| |
| This is an implementation of pmdp_establish() that is only suitable for |
| an architecture that doesn't have hardware dirty/accessed bits. In this |
| case we can't race with CPU which sets these bits and non-atomic |
| approach is fine. |
| |
| Link: http://lkml.kernel.org/r/20171213105756.69879-2-kirill.shutemov@linux.intel.com |
| Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> |
| Cc: Vlastimil Babka <vbabka@suse.cz> |
| Cc: Andrea Arcangeli <aarcange@redhat.com> |
| Cc: Michal Hocko <mhocko@kernel.org> |
| Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> |
| Cc: Catalin Marinas <catalin.marinas@arm.com> |
| Cc: David Daney <david.daney@cavium.com> |
| Cc: David Miller <davem@davemloft.net> |
| Cc: H. Peter Anvin <hpa@zytor.com> |
| Cc: Hugh Dickins <hughd@google.com> |
| Cc: Ingo Molnar <mingo@kernel.org> |
| Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> |
| Cc: Nitin Gupta <nitin.m.gupta@oracle.com> |
| Cc: Ralf Baechle <ralf@linux-mips.org> |
| Cc: Thomas Gleixner <tglx@linutronix.de> |
| Cc: Vineet Gupta <vgupta@synopsys.com> |
| Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
| Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
| Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| include/asm-generic/pgtable.h | 15 +++++++++++++++ |
| 1 file changed, 15 insertions(+) |
| |
| --- a/include/asm-generic/pgtable.h |
| +++ b/include/asm-generic/pgtable.h |
| @@ -234,6 +234,21 @@ extern void pgtable_trans_huge_deposit(s |
| extern pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp); |
| #endif |
| |
| +#ifdef CONFIG_TRANSPARENT_HUGEPAGE |
| +/* |
| + * This is an implementation of pmdp_establish() that is only suitable for an |
| + * architecture that doesn't have hardware dirty/accessed bits. In this case we |
| + * can't race with CPU which sets these bits and non-atomic aproach is fine. |
| + */ |
| +static inline pmd_t generic_pmdp_establish(struct vm_area_struct *vma, |
| + unsigned long address, pmd_t *pmdp, pmd_t pmd) |
| +{ |
| + pmd_t old_pmd = *pmdp; |
| + set_pmd_at(vma->vm_mm, address, pmdp, pmd); |
| + return old_pmd; |
| +} |
| +#endif |
| + |
| #ifndef __HAVE_ARCH_PMDP_INVALIDATE |
| extern void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address, |
| pmd_t *pmdp); |