netfs: Prepare to split read_helper.c

Rename netfs_rreq_unlock() to netfs_rreq_unlock_folios() to make it sound
less like it's dropping a lock on an netfs_io_request struct.

Remove the 'static' marker on netfs_rreq_unlock_folios() and declaring it
in internal.h preparatory to splitting the file.

Changes
=======
ver #2)
 - Slide this patch to after the one adding netfs_begin_read().
 - As a consequence, don't need to unstatic so many functions.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/164623002861.3564931.17340149482236413375.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/164678215208.1200972.9761906209395002182.stgit@warthog.procyon.org.uk/ # v2

fs/netfs/internal.h

@@ -15,6 +15,11 @@
 
 #define pr_fmt(fmt) "netfs: " fmt
 
+/*
+ * buffered_read.c
+ */
+void netfs_rreq_unlock_folios(struct netfs_io_request *rreq);
+
 /*
  * objects.c
  */

fs/netfs/read_helper.c

@@ -250,7 +250,7 @@ static void netfs_rreq_write_to_cache(struct netfs_io_request *rreq)
  * Unlock the folios in a read operation.  We need to set PG_fscache on any
  * folios we're going to write back before we unlock them.
  */
-static void netfs_rreq_unlock(struct netfs_io_request *rreq)
+void netfs_rreq_unlock_folios(struct netfs_io_request *rreq)
 {
 	struct netfs_io_subrequest *subreq;
 	struct folio *folio;
@@ -432,7 +432,7 @@ static void netfs_rreq_assess(struct netfs_io_request *rreq, bool was_async)
 		return;
 	}
 
-	netfs_rreq_unlock(rreq);
+	netfs_rreq_unlock_folios(rreq);
 
 	clear_bit_unlock(NETFS_RREQ_IN_PROGRESS, &rreq->flags);
 	wake_up_bit(&rreq->flags, NETFS_RREQ_IN_PROGRESS);