diff mbox series

[05/10] mm/hugetlb: Make userfaultfd_huge_must_wait() safe to pmd unshare

Message ID 20221129193526.3588187-6-peterx@redhat.com
State New
Headers
Series [01/10] mm/hugetlb: Let vma_offset_start() to return start |

Commit Message

Peter Xu Nov. 29, 2022, 7:35 p.m. UTC 
  We can take the hugetlb walker lock, here taking vma lock directly.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 fs/userfaultfd.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

Comments

David Hildenbrand Nov. 30, 2022, 4:08 p.m. UTC | #1 
On 29.11.22 20:35, Peter Xu wrote:
> We can take the hugetlb walker lock, here taking vma lock directly.
> 
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---

Reviewed-by: David Hildenbrand <david@redhat.com>
Mike Kravetz Dec. 5, 2022, 10:23 p.m. UTC | #2 
On 11/29/22 14:35, Peter Xu wrote:
> We can take the hugetlb walker lock, here taking vma lock directly.
> 
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  fs/userfaultfd.c | 18 ++++++++++++++----
>  1 file changed, 14 insertions(+), 4 deletions(-)

Looks good.

Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
diff mbox series

Patch

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 07c81ab3fd4d..a602f008dde5 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -376,7 +376,8 @@  static inline unsigned int userfaultfd_get_blocking_state(unsigned int flags)
  */
 vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason)
 {
-	struct mm_struct *mm = vmf->vma->vm_mm;
+	struct vm_area_struct *vma = vmf->vma;
+	struct mm_struct *mm = vma->vm_mm;
 	struct userfaultfd_ctx *ctx;
 	struct userfaultfd_wait_queue uwq;
 	vm_fault_t ret = VM_FAULT_SIGBUS;
@@ -403,7 +404,7 @@  vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason)
 	 */
 	mmap_assert_locked(mm);
 
-	ctx = vmf->vma->vm_userfaultfd_ctx.ctx;
+	ctx = vma->vm_userfaultfd_ctx.ctx;
 	if (!ctx)
 		goto out;
 
@@ -493,6 +494,13 @@  vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason)
 
 	blocking_state = userfaultfd_get_blocking_state(vmf->flags);
 
+	/*
+	 * This stablizes pgtable for hugetlb on e.g. pmd unsharing.  Need
+	 * to be before setting current state.
+	 */
+	if (is_vm_hugetlb_page(vma))
+		hugetlb_vma_lock_read(vma);
+
 	spin_lock_irq(&ctx->fault_pending_wqh.lock);
 	/*
 	 * After the __add_wait_queue the uwq is visible to userland
@@ -507,13 +515,15 @@  vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason)
 	set_current_state(blocking_state);
 	spin_unlock_irq(&ctx->fault_pending_wqh.lock);
 
-	if (!is_vm_hugetlb_page(vmf->vma))
+	if (!is_vm_hugetlb_page(vma))
 		must_wait = userfaultfd_must_wait(ctx, vmf->address, vmf->flags,
 						  reason);
 	else
-		must_wait = userfaultfd_huge_must_wait(ctx, vmf->vma,
+		must_wait = userfaultfd_huge_must_wait(ctx, vma,
 						       vmf->address,
 						       vmf->flags, reason);
+	if (is_vm_hugetlb_page(vma))
+		hugetlb_vma_unlock_read(vma);
 	mmap_read_unlock(mm);
 
 	if (likely(must_wait && !READ_ONCE(ctx->released))) {