userfaultfd: shmem: add shmem_mfill_zeropage_pte for userfaultfd support
shmem_mfill_zeropage_pte is the low level routine that implements the
userfaultfd UFFDIO_ZEROPAGE command. Since for shmem mappings zero
pages are always allocated and accounted, the new method is a slight
extension of the existing shmem_mcopy_atomic_pte.
Link: http://lkml.kernel.org/r/1497939652-16528-4-git-send-email-rppt@linux.vnet.ibm.com
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index a7d6bd2..b6c3540 100644
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -137,9 +137,15 @@ extern int shmem_mcopy_atomic_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd,
unsigned long dst_addr,
unsigned long src_addr,
struct page **pagep);
+extern int shmem_mfill_zeropage_pte(struct mm_struct *dst_mm,
+ pmd_t *dst_pmd,
+ struct vm_area_struct *dst_vma,
+ unsigned long dst_addr);
#else
#define shmem_mcopy_atomic_pte(dst_mm, dst_pte, dst_vma, dst_addr, \
src_addr, pagep) ({ BUG(); 0; })
+#define shmem_mfill_zeropage_pte(dst_mm, dst_pmd, dst_vma, \
+ dst_addr) ({ BUG(); 0; })
#endif
#endif