Revert "mm: replace p??_write with pte_access_permitted in fault + gup paths"

[tomoyo/tomoyo-test1.git] / mm / gup.c

diff --git a/mm/gup.c b/mm/gup.c
index dfcde13..e0d82b6 100644 (file)
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1095,6 +1095,70 @@ long get_user_pages(unsigned long start, unsigned long nr_pages,
 }
 EXPORT_SYMBOL(get_user_pages);
 
+#ifdef CONFIG_FS_DAX
+/*
+ * This is the same as get_user_pages() in that it assumes we are
+ * operating on the current task's mm, but it goes further to validate
+ * that the vmas associated with the address range are suitable for
+ * longterm elevated page reference counts. For example, filesystem-dax
+ * mappings are subject to the lifetime enforced by the filesystem and
+ * we need guarantees that longterm users like RDMA and V4L2 only
+ * establish mappings that have a kernel enforced revocation mechanism.
+ *
+ * "longterm" == userspace controlled elevated page count lifetime.
+ * Contrast this to iov_iter_get_pages() usages which are transient.
+ */
+long get_user_pages_longterm(unsigned long start, unsigned long nr_pages,
+               unsigned int gup_flags, struct page **pages,
+               struct vm_area_struct **vmas_arg)
+{
+       struct vm_area_struct **vmas = vmas_arg;
+       struct vm_area_struct *vma_prev = NULL;
+       long rc, i;
+
+       if (!pages)
+               return -EINVAL;
+
+       if (!vmas) {
+               vmas = kcalloc(nr_pages, sizeof(struct vm_area_struct *),
+                              GFP_KERNEL);
+               if (!vmas)
+                       return -ENOMEM;
+       }
+
+       rc = get_user_pages(start, nr_pages, gup_flags, pages, vmas);
+
+       for (i = 0; i < rc; i++) {
+               struct vm_area_struct *vma = vmas[i];
+
+               if (vma == vma_prev)
+                       continue;
+
+               vma_prev = vma;
+
+               if (vma_is_fsdax(vma))
+                       break;
+       }
+
+       /*
+        * Either get_user_pages() failed, or the vma validation
+        * succeeded, in either case we don't need to put_page() before
+        * returning.
+        */
+       if (i >= rc)
+               goto out;
+
+       for (i = 0; i < rc; i++)
+               put_page(pages[i]);
+       rc = -EOPNOTSUPP;
+out:
+       if (vmas != vmas_arg)
+               kfree(vmas);
+       return rc;
+}
+EXPORT_SYMBOL(get_user_pages_longterm);
+#endif /* CONFIG_FS_DAX */
+
 /**
  * populate_vma_page_range() -  populate a range of pages in the vma.
  * @vma:   target vma