mm: change return type to vm_fault_t

Use new return type vm_fault_t for fault handler in struct
vm_operations_struct.  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 1c8f422 ("mm: change return type to vm_fault_t")

Link: http://lkml.kernel.org/r/20180512063745.GA26866@jordon-HP-15-Notebook-PC
Signed-off-by: Souptick Joarder <[email protected]>
Reviewed-by: Matthew Wilcox <[email protected]>
Reviewed-by: Andrew Morton <[email protected]>
Cc: Joe Perches <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Cc: Aneesh Kumar K.V <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: Souptick Joarder

include/linux/mm_types.h

@@ -629,9 +629,9 @@ struct vm_special_mapping {
 	 * If non-NULL, then this is called to resolve page faults
 	 * on the special mapping.  If used, .pages is not checked.
 	 */
-	int (*fault)(const struct vm_special_mapping *sm,
-		     struct vm_area_struct *vma,
-		     struct vm_fault *vmf);
+	vm_fault_t (*fault)(const struct vm_special_mapping *sm,
+				struct vm_area_struct *vma,
+				struct vm_fault *vmf);
 
 	int (*mremap)(const struct vm_special_mapping *sm,
 		     struct vm_area_struct *new_vma);

mm/hugetlb.c

@@ -3159,7 +3159,7 @@ static unsigned long hugetlb_vm_op_pagesize(struct vm_area_struct *vma)
  * hugegpage VMA.  do_page_fault() is supposed to trap this, so BUG is we get
  * this far.
  */
-static int hugetlb_vm_op_fault(struct vm_fault *vmf)
+static vm_fault_t hugetlb_vm_op_fault(struct vm_fault *vmf)
 {
 	BUG();
 	return 0;

mm/mmap.c

@@ -3277,7 +3277,7 @@ void vm_stat_account(struct mm_struct *mm, vm_flags_t flags, long npages)
 		mm->data_vm += npages;
 }
 
-static int special_mapping_fault(struct vm_fault *vmf);
+static vm_fault_t special_mapping_fault(struct vm_fault *vmf);
 
 /*
  * Having a close hook prevents vma merging regardless of flags.
@@ -3316,7 +3316,7 @@ static const struct vm_operations_struct legacy_special_mapping_vmops = {
 	.fault = special_mapping_fault,
 };
 
-static int special_mapping_fault(struct vm_fault *vmf)
+static vm_fault_t special_mapping_fault(struct vm_fault *vmf)
 {
 	struct vm_area_struct *vma = vmf->vma;
 	pgoff_t pgoff;