netfs: Rename read_helper.c to io.c

Rename the read_helper.c file to io.c before splitting out the buffered
read functions and some other bits.

Changes
=======
ver #2)
 - Rename read_helper.c before splitting.

Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/164678216109.1200972.16567696909952495832.stgit@warthog.procyon.org.uk/ # v2

Author: dhowells

Documentation/filesystems/netfs_library.rst

@@ -604,4 +604,5 @@ API Function Reference
 ======================
 
 .. kernel-doc:: include/linux/netfs.h
-.. kernel-doc:: fs/netfs/read_helper.c
+.. kernel-doc:: fs/netfs/buffered_read.c
+.. kernel-doc:: fs/netfs/io.c

fs/netfs/Makefile

@@ -1,8 +1,8 @@
 # SPDX-License-Identifier: GPL-2.0
 
 netfs-y := \
-	objects.o \
-	read_helper.o
+	io.o \
+	objects.o
 
 netfs-$(CONFIG_NETFS_STATS) += stats.o
 

fs/netfs/internal.h

@@ -20,6 +20,13 @@
  */
 void netfs_rreq_unlock_folios(struct netfs_io_request *rreq);
 
+/*
+ * io.c
+ */
+extern unsigned int netfs_debug;
+
+int netfs_begin_read(struct netfs_io_request *rreq, bool sync);
+
 /*
  * objects.c
  */
@@ -39,13 +46,6 @@ static inline void netfs_see_request(struct netfs_io_request *rreq,
 	trace_netfs_rreq_ref(rreq->debug_id, refcount_read(&rreq->ref), what);
 }
 
-/*
- * read_helper.c
- */
-extern unsigned int netfs_debug;
-
-int netfs_begin_read(struct netfs_io_request *rreq, bool sync);
-
 /*
  * stats.c
  */