[PATCH v6 14/23] mm/hugetlb: Handle UFFDIO_WRITEPROTECT

Peter Xu
2021-11-15T08:04:05Z

This starts from passing cp_flags into hugetlb_change_protection() so hugetlb
will be able to handle MM_CP_UFFD_WP[_RESOLVE] requests.

huge_pte_clear_uffd_wp() is introduced to handle the case where the
UFFDIO_WRITEPROTECT is requested upon migrating huge page entries.

Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
include/linux/hugetlb.h | 6 ++++--
mm/hugetlb.c | 13 ++++++++++++-
mm/mprotect.c | 3 ++-
mm/userfaultfd.c | 8 ++++++++
4 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 4da0c4b4159a..a46011510e49 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -210,7 +210,8 @@ struct page *follow_huge_pgd(struct mm_struct *mm, unsigned long address,
int pmd_huge(pmd_t pmd);
int pud_huge(pud_t pud);
unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
- unsigned long address, unsigned long end, pgprot_t newprot);
+ unsigned long address, unsigned long end, pgprot_t newprot,
+ unsigned long cp_flags);

bool is_hugetlb_entry_migration(pte_t pte);
void hugetlb_unshare_all_pmds(struct vm_area_struct *vma);
@@ -391,7 +392,8 @@ static inline void move_hugetlb_state(struct page *oldpage,

static inline unsigned long hugetlb_change_protection(
struct vm_area_struct *vma, unsigned long address,
- unsigned long end, pgprot_t newprot)
+ unsigned long end, pgprot_t newprot,
+ unsigned long cp_flags)
{
return 0;
}
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 8146240eefc6..7fc213c0ebf8 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -6127,7 +6127,8 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
}

unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
- unsigned long address, unsigned long end, pgprot_t newprot)
+ unsigned long address, unsigned long end,
+ pgprot_t newprot, unsigned long cp_flags)
{
struct mm_struct *mm = vma->vm_mm;
unsigned long start = address;
@@ -6137,6 +6138,8 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
unsigned long pages = 0;
bool shared_pmd = false;
struct mmu_notifier_range range;
+ bool uffd_wp = cp_flags & MM_CP_UFFD_WP;
+ bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE;

/*
* In the case of shared PMDs, the area to flush could be beyond
@@ -6178,6 +6181,10 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
entry = make_readable_migration_entry(
swp_offset(entry));
newpte = swp_entry_to_pte(entry);
+ if (uffd_wp)
+ newpte = pte_swp_mkuffd_wp(newpte);
+ else if (uffd_wp_resolve)
+ newpte = pte_swp_clear_uffd_wp(newpte);
set_huge_swap_pte_at(mm, address, ptep,
newpte, huge_page_size(h));
pages++;
@@ -6192,6 +6199,10 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
old_pte = huge_ptep_modify_prot_start(vma, address, ptep);
pte = pte_mkhuge(huge_pte_modify(old_pte, newprot));
pte = arch_make_huge_pte(pte, shift, vma->vm_flags);
+ if (uffd_wp)
+ pte = huge_pte_mkuffd_wp(huge_pte_wrprotect(pte));
+ else if (uffd_wp_resolve)
+ pte = huge_pte_clear_uffd_wp(pte);
huge_ptep_modify_prot_commit(vma, address, ptep, old_pte, pte);
pages++;
}
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 0d4bf755cee8..1cc4a6d1886b 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -441,7 +441,8 @@ unsigned long change_protection(struct vm_area_struct *vma, unsigned long start,
BUG_ON((cp_flags & MM_CP_UFFD_WP_ALL) == MM_CP_UFFD_WP_ALL);

if (is_vm_hugetlb_page(vma))
- pages = hugetlb_change_protection(vma, start, end, newprot);
+ pages = hugetlb_change_protection(vma, start, end, newprot,
+ cp_flags);
else
pages = change_protection_range(vma, start, end, newprot,
cp_flags);
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 6174a212c72f..037f82719e64 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -690,6 +690,7 @@ int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start,
atomic_t *mmap_changing)
{
struct vm_area_struct *dst_vma;
+ unsigned long page_mask;
pgprot_t newprot;
int err;

@@ -726,6 +727,13 @@ int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start,
if (!vma_is_anonymous(dst_vma))
goto out_unlock;

+ if (is_vm_hugetlb_page(dst_vma)) {
+ err = -EINVAL;
+ page_mask = vma_kernel_pagesize(dst_vma) - 1;
+ if ((start & page_mask) || (len & page_mask))
+ goto out_unlock;
+ }
+
if (enable_wp)
newprot = vm_get_page_prot(dst_vma->vm_flags & ~(VM_WRITE));
else
--
2.32.0