mm: Change return type int to vm_fault_t for fault handlers

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.

[akpm@linux-foundation.org: don't shadow outer local `ret' in __do_huge_pmd_anonymous_page()]
Link: http://lkml.kernel.org/r/20180604171727.GA20279@jordon-HP-15-Notebook-PC
Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Reviewed-by: Matthew Wilcox <mawilcox@microsoft.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/gup.c b/mm/gup.c
index fc5f980..1abc8b4 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -497,7 +497,7 @@
 		unsigned long address, unsigned int *flags, int *nonblocking)
 {
 	unsigned int fault_flags = 0;
-	int ret;
+	vm_fault_t ret;
 
 	/* mlock all present pages, but do not fault in new pages */
 	if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK)
@@ -818,7 +818,7 @@
 		     bool *unlocked)
 {
 	struct vm_area_struct *vma;
-	int ret, major = 0;
+	vm_fault_t ret, major = 0;
 
 	if (unlocked)
 		fault_flags |= FAULT_FLAG_ALLOW_RETRY;