userfaultfd: shmem: use shmem_mcopy_atomic_pte for shared memory

The shmem_mcopy_atomic_pte implements low lever part of UFFDIO_COPY
operation for shared memory VMAs.  It's based on mcopy_atomic_pte with
adjustments necessary for shared memory pages.

Link: http://lkml.kernel.org/r/20161216144821.5183-32-aarcange@redhat.com
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Michael Rapoport <RAPOPORT@il.ibm.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 31207b47ea92ac9d728b39eb237ccc5affe60b73..a0817cc470b0067001b5bb08016faa3248251693 100644 (file)
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -16,6 +16,7 @@
 #include <linux/mmu_notifier.h>
 #include <linux/hugetlb.h>
 #include <linux/pagemap.h>
+#include <linux/shmem_fs.h>
 #include <asm/tlbflush.h>
 #include "internal.h"
 
@@ -369,7 +370,9 @@ retry:
         */
        err = -EINVAL;
        dst_vma = find_vma(dst_mm, dst_start);
-       if (!dst_vma || (dst_vma->vm_flags & VM_SHARED))
+       if (!dst_vma)
+               goto out_unlock;
+       if (!vma_is_shmem(dst_vma) && dst_vma->vm_flags & VM_SHARED)
                goto out_unlock;
        if (dst_start < dst_vma->vm_start ||
            dst_start + len > dst_vma->vm_end)
@@ -394,11 +397,7 @@ retry:
        if (!dst_vma->vm_userfaultfd_ctx.ctx)
                goto out_unlock;
 
-       /*
-        * FIXME: only allow copying on anonymous vmas, tmpfs should
-        * be added.
-        */
-       if (!vma_is_anonymous(dst_vma))
+       if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma))
                goto out_unlock;
 
        /*
@@ -407,7 +406,7 @@ retry:
         * dst_vma.
         */
        err = -ENOMEM;
-       if (unlikely(anon_vma_prepare(dst_vma)))
+       if (vma_is_anonymous(dst_vma) && unlikely(anon_vma_prepare(dst_vma)))
                goto out_unlock;
 
        while (src_addr < src_start + len) {
@@ -444,12 +443,21 @@ retry:
                BUG_ON(pmd_none(*dst_pmd));
                BUG_ON(pmd_trans_huge(*dst_pmd));
 
-               if (!zeropage)
-                       err = mcopy_atomic_pte(dst_mm, dst_pmd, dst_vma,
-                                              dst_addr, src_addr, &page);
-               else
-                       err = mfill_zeropage_pte(dst_mm, dst_pmd, dst_vma,
-                                                dst_addr);
+               if (vma_is_anonymous(dst_vma)) {
+                       if (!zeropage)
+                               err = mcopy_atomic_pte(dst_mm, dst_pmd, dst_vma,
+                                                      dst_addr, src_addr,
+                                                      &page);
+                       else
+                               err = mfill_zeropage_pte(dst_mm, dst_pmd,
+                                                        dst_vma, dst_addr);
+               } else {
+                       err = -EINVAL; /* if zeropage is true return -EINVAL */
+                       if (likely(!zeropage))
+                               err = shmem_mcopy_atomic_pte(dst_mm, dst_pmd,
+                                                            dst_vma, dst_addr,
+                                                            src_addr, &page);
+               }
 
                cond_resched();