Re: [PATCH v4 08/23] vfio, mm: fix get_user_pages_remote() and FOLL_LONGTERM

[John Hubbard]

On 11/13/19 11:17 AM, Ira Weiny wrote:
...

@@ -348,33 +347,13 @@ static int vaddr_get_pfn(struct mm_struct *mm, unsigned 
long vaddr,
                flags |= FOLL_WRITE;

down_read(&mm->mmap_sem);

-       if (mm == current->mm) {
-               ret = get_user_pages(vaddr, 1, flags | FOLL_LONGTERM, page,
-                                    vmas);
-       } else {
-               ret = get_user_pages_remote(NULL, mm, vaddr, 1, flags, page,
-                                           vmas, NULL);
-               /*
-                * The lifetime of a vaddr_get_pfn() page pin is
-                * userspace-controlled. In the fs-dax case this could
-                * lead to indefinite stalls in filesystem operations.
-                * Disallow attempts to pin fs-dax pages via this
-                * interface.
-                */
-               if (ret > 0 && vma_is_fsdax(vmas[0])) {
-                       ret = -EOPNOTSUPP;
-                       put_page(page[0]);
-               }
-       }
-       up_read(&mm->mmap_sem);
-
+       ret = get_user_pages_remote(NULL, mm, vaddr, 1, flags | FOLL_LONGTERM,
+                                   page, NULL, NULL);
        if (ret == 1) {
                *pfn = page_to_pfn(page[0]);
                return 0;

Mind the return with the lock held this needs some goto unwind

Ah yea...  retract my reviewed by...  :-(

ooops, embarrassed that I missed that, good catch. Will repost with it fixed.



thanks,
--
John Hubbard
NVIDIA