On Mon, 4 Jun 2018 22:47:27 +0530 Souptick Joarder [off-list ref] wrote:

Use new return type vm_fault_t for fault handler. For
now, this is just documenting that the function returns
a VM_FAULT value rather than an errno. Once all instances
are converted, vm_fault_t will become a distinct type.

Ref-> commit 1c8f422059ae ("mm: change return type to vm_fault_t")

The aim is to change the return type of finish_fault()
and handle_mm_fault() to vm_fault_t type. As part of
that clean up return type of all other recursively called
functions have been changed to vm_fault_t type.

The places from where handle_mm_fault() is getting invoked
will be change to vm_fault_t type but in a separate patch.

vmf_error() is the newly introduce inline function
in 4.17-rc6.

Looks OK.

For some reason the shmem.c changes are already present.

One incidental fixup:

From: Andrew Morton <akpm@linux-foundation.org>
Subject: mm-change-return-type-int-to-vm_fault_t-for-fault-handlers-fix

don't shadow outer local `ret' in __do_huge_pmd_anonymous_page()

--- a/mm/huge_memory.c~mm-change-return-type-int-to-vm_fault_t-for-fault-handlers-fix
+++ a/mm/huge_memory.c

@@ -584,15 +584,15 @@ static vm_fault_t __do_huge_pmd_anonymou
 
 		/* Deliver the page fault to userland */
 		if (userfaultfd_missing(vma)) {
-			vm_fault_t ret;
+			vm_fault_t ret2;
 
 			spin_unlock(vmf->ptl);
 			mem_cgroup_cancel_charge(page, memcg, true);
 			put_page(page);
 			pte_free(vma->vm_mm, pgtable);
-			ret = handle_userfault(vmf, VM_UFFD_MISSING);
-			VM_BUG_ON(ret & VM_FAULT_FALLBACK);
-			return ret;
+			ret2 = handle_userfault(vmf, VM_UFFD_MISSING);
+			VM_BUG_ON(ret2 & VM_FAULT_FALLBACK);
+			return ret2;
 		}
 
 		entry = mk_huge_pmd(page, vma->vm_page_prot);