afs: use find_get_pages_range_tag()

Use find_get_pages_range_tag() in afs_writepages_region() as we are
interested only in pages from given range.  Remove unnecessary code
after this conversion.

Link: http://lkml.kernel.org/r/20171009151359.31984-16-jack@suse.cz
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/afs/write.c

@@ -497,20 +497,13 @@ static int afs_writepages_region(struct address_space *mapping,
 	_enter(",,%lx,%lx,", index, end);
 
 	do {
-		n = find_get_pages_tag(mapping, &index, PAGECACHE_TAG_DIRTY,
-				       1, &page);
+		n = find_get_pages_range_tag(mapping, &index, end,
+					PAGECACHE_TAG_DIRTY, 1, &page);
 		if (!n)
 			break;
 
 		_debug("wback %lx", page->index);
 
-		if (page->index > end) {
-			*_next = index;
-			put_page(page);
-			_leave(" = 0 [%lx]", *_next);
-			return 0;
-		}
-
 		/* at this point we hold neither mapping->tree_lock nor lock on
 		 * the page itself: the page may be truncated or invalidated
 		 * (changing page->mapping to NULL), or even swizzled back from