mm/shmem.c: use new return type vm_fault_t

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.

See commit 1c8f4220 ("mm: change return type to vm_fault_t")

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

Link: http://lkml.kernel.org/r/20180521202410.GA17912@jordon-HP-15-Notebook-PCSigned-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Reviewed-by: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/shmem.c

@@ -1947,14 +1947,14 @@ static int synchronous_wake_function(wait_queue_entry_t *wait, unsigned mode, in
 	return ret;
 }
 
-static int shmem_fault(struct vm_fault *vmf)
+static vm_fault_t shmem_fault(struct vm_fault *vmf)
 {
 	struct vm_area_struct *vma = vmf->vma;
 	struct inode *inode = file_inode(vma->vm_file);
 	gfp_t gfp = mapping_gfp_mask(inode->i_mapping);
 	enum sgp_type sgp;
-	int error;
-	int ret = VM_FAULT_LOCKED;
+	int err;
+	vm_fault_t ret = VM_FAULT_LOCKED;
 
 	/*
 	 * Trinity finds that probing a hole which tmpfs is punching can
@@ -2022,10 +2022,10 @@ static int shmem_fault(struct vm_fault *vmf)
 	else if (vma->vm_flags & VM_HUGEPAGE)
 		sgp = SGP_HUGE;
 
-	error = shmem_getpage_gfp(inode, vmf->pgoff, &vmf->page, sgp,
+	err = shmem_getpage_gfp(inode, vmf->pgoff, &vmf->page, sgp,
 				  gfp, vma, vmf, &ret);
-	if (error)
-		return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
+	if (err)
+		return vmf_error(err);
 	return ret;
 }