On Tue, Feb 12, 2019 at 10:56:23AM +0800, Peter Xu wrote: > For either swap and page migration, we all use the bit 2 of the entry to > identify whether this entry is uffd write-protected. It plays a similar > role as the existing soft dirty bit in swap entries but only for keeping > the uffd-wp tracking for a specific PTE/PMD. > > Something special here is that when we want to recover the uffd-wp bit > from a swap/migration entry to the PTE bit we'll also need to take care > of the _PAGE_RW bit and make sure it's cleared, otherwise even with the > _PAGE_UFFD_WP bit we can't trap it at all. > > Note that this patch removed two lines from "userfaultfd: wp: hook > userfault handler to write protection fault" where we try to remove the > VM_FAULT_WRITE from vmf->flags when uffd-wp is set for the VMA. This > patch will still keep the write flag there. > > Signed-off-by: Peter Xu <[email protected]>
Reviewed-by: Mike Rapoport <[email protected]> > --- > include/linux/swapops.h | 2 ++ > mm/huge_memory.c | 3 +++ > mm/memory.c | 8 ++++++-- > mm/migrate.c | 7 +++++++ > mm/mprotect.c | 2 ++ > mm/rmap.c | 6 ++++++ > 6 files changed, 26 insertions(+), 2 deletions(-) > > diff --git a/include/linux/swapops.h b/include/linux/swapops.h > index 4d961668e5fc..0c2923b1cdb7 100644 > --- a/include/linux/swapops.h > +++ b/include/linux/swapops.h > @@ -68,6 +68,8 @@ static inline swp_entry_t pte_to_swp_entry(pte_t pte) > > if (pte_swp_soft_dirty(pte)) > pte = pte_swp_clear_soft_dirty(pte); > + if (pte_swp_uffd_wp(pte)) > + pte = pte_swp_clear_uffd_wp(pte); > arch_entry = __pte_to_swp_entry(pte); > return swp_entry(__swp_type(arch_entry), __swp_offset(arch_entry)); > } > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index fb2234cb595a..75de07141801 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -2175,6 +2175,7 @@ static void __split_huge_pmd_locked(struct > vm_area_struct *vma, pmd_t *pmd, > write = is_write_migration_entry(entry); > young = false; > soft_dirty = pmd_swp_soft_dirty(old_pmd); > + uffd_wp = pmd_swp_uffd_wp(old_pmd); > } else { > page = pmd_page(old_pmd); > if (pmd_dirty(old_pmd)) > @@ -2207,6 +2208,8 @@ static void __split_huge_pmd_locked(struct > vm_area_struct *vma, pmd_t *pmd, > entry = swp_entry_to_pte(swp_entry); > if (soft_dirty) > entry = pte_swp_mksoft_dirty(entry); > + if (uffd_wp) > + entry = pte_swp_mkuffd_wp(entry); > } else { > entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot)); > entry = maybe_mkwrite(entry, vma); > diff --git a/mm/memory.c b/mm/memory.c > index c2035539e9fd..7cee990d67cf 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -736,6 +736,8 @@ copy_one_pte(struct mm_struct *dst_mm, struct mm_struct > *src_mm, > pte = swp_entry_to_pte(entry); > if (pte_swp_soft_dirty(*src_pte)) > pte = pte_swp_mksoft_dirty(pte); > + if (pte_swp_uffd_wp(*src_pte)) > + pte = pte_swp_mkuffd_wp(pte); > set_pte_at(src_mm, addr, src_pte, pte); > } > } else if (is_device_private_entry(entry)) { > @@ -2815,8 +2817,6 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) > inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES); > dec_mm_counter_fast(vma->vm_mm, MM_SWAPENTS); > pte = mk_pte(page, vma->vm_page_prot); > - if (userfaultfd_wp(vma)) > - vmf->flags &= ~FAULT_FLAG_WRITE; > if ((vmf->flags & FAULT_FLAG_WRITE) && reuse_swap_page(page, NULL)) { > pte = maybe_mkwrite(pte_mkdirty(pte), vma); > vmf->flags &= ~FAULT_FLAG_WRITE; > @@ -2826,6 +2826,10 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) > flush_icache_page(vma, page); > if (pte_swp_soft_dirty(vmf->orig_pte)) > pte = pte_mksoft_dirty(pte); > + if (pte_swp_uffd_wp(vmf->orig_pte)) { > + pte = pte_mkuffd_wp(pte); > + pte = pte_wrprotect(pte); > + } > set_pte_at(vma->vm_mm, vmf->address, vmf->pte, pte); > arch_do_swap_page(vma->vm_mm, vma, vmf->address, pte, vmf->orig_pte); > vmf->orig_pte = pte; > diff --git a/mm/migrate.c b/mm/migrate.c > index d4fd680be3b0..605ccd1f5c64 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -242,6 +242,11 @@ static bool remove_migration_pte(struct page *page, > struct vm_area_struct *vma, > if (is_write_migration_entry(entry)) > pte = maybe_mkwrite(pte, vma); > > + if (pte_swp_uffd_wp(*pvmw.pte)) { > + pte = pte_mkuffd_wp(pte); > + pte = pte_wrprotect(pte); > + } > + > if (unlikely(is_zone_device_page(new))) { > if (is_device_private_page(new)) { > entry = make_device_private_entry(new, > pte_write(pte)); > @@ -2290,6 +2295,8 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, > swp_pte = swp_entry_to_pte(entry); > if (pte_soft_dirty(pte)) > swp_pte = pte_swp_mksoft_dirty(swp_pte); > + if (pte_uffd_wp(pte)) > + swp_pte = pte_swp_mkuffd_wp(swp_pte); > set_pte_at(mm, addr, ptep, swp_pte); > > /* > diff --git a/mm/mprotect.c b/mm/mprotect.c > index ae93721f3795..73a65f07fe41 100644 > --- a/mm/mprotect.c > +++ b/mm/mprotect.c > @@ -187,6 +187,8 @@ static unsigned long change_pte_range(struct > vm_area_struct *vma, pmd_t *pmd, > newpte = swp_entry_to_pte(entry); > if (pte_swp_soft_dirty(oldpte)) > newpte = pte_swp_mksoft_dirty(newpte); > + if (pte_swp_uffd_wp(oldpte)) > + newpte = pte_swp_mkuffd_wp(newpte); > set_pte_at(mm, addr, pte, newpte); > > pages++; > diff --git a/mm/rmap.c b/mm/rmap.c > index 0454ecc29537..3750d5a5283c 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -1469,6 +1469,8 @@ static bool try_to_unmap_one(struct page *page, struct > vm_area_struct *vma, > swp_pte = swp_entry_to_pte(entry); > if (pte_soft_dirty(pteval)) > swp_pte = pte_swp_mksoft_dirty(swp_pte); > + if (pte_uffd_wp(pteval)) > + swp_pte = pte_swp_mkuffd_wp(swp_pte); > set_pte_at(mm, pvmw.address, pvmw.pte, swp_pte); > /* > * No need to invalidate here it will synchronize on > @@ -1561,6 +1563,8 @@ static bool try_to_unmap_one(struct page *page, struct > vm_area_struct *vma, > swp_pte = swp_entry_to_pte(entry); > if (pte_soft_dirty(pteval)) > swp_pte = pte_swp_mksoft_dirty(swp_pte); > + if (pte_uffd_wp(pteval)) > + swp_pte = pte_swp_mkuffd_wp(swp_pte); > set_pte_at(mm, address, pvmw.pte, swp_pte); > /* > * No need to invalidate here it will synchronize on > @@ -1627,6 +1631,8 @@ static bool try_to_unmap_one(struct page *page, struct > vm_area_struct *vma, > swp_pte = swp_entry_to_pte(entry); > if (pte_soft_dirty(pteval)) > swp_pte = pte_swp_mksoft_dirty(swp_pte); > + if (pte_uffd_wp(pteval)) > + swp_pte = pte_swp_mkuffd_wp(swp_pte); > set_pte_at(mm, address, pvmw.pte, swp_pte); > /* Invalidate as we cleared the pte */ > mmu_notifier_invalidate_range(mm, address, > -- > 2.17.1 > -- Sincerely yours, Mike.
