libceph: drop msg argument from ceph_osdc_callback_t

finish_read(), its only user, uses it to get to hdr.data_len, which is
what ->r_result is set to on success.  This gains us the ability to
safely call callbacks from contexts other than reply, e.g. map check.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index 59b3c3f..a11756a 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -257,12 +257,12 @@
 /*
  * Finish an async read(ahead) op.
  */
-static void finish_read(struct ceph_osd_request *req, struct ceph_msg *msg)
+static void finish_read(struct ceph_osd_request *req)
 {
 	struct inode *inode = req->r_inode;
 	struct ceph_osd_data *osd_data;
-	int rc = req->r_result;
-	int bytes = le32_to_cpu(msg->hdr.data_len);
+	int rc = req->r_result <= 0 ? req->r_result : 0;
+	int bytes = req->r_result >= 0 ? req->r_result : 0;
 	int num_pages;
 	int i;
 
@@ -598,8 +598,7 @@
  * If we get an error, set the mapping error bit, but not the individual
  * page error bits.
  */
-static void writepages_finish(struct ceph_osd_request *req,
-			      struct ceph_msg *msg)
+static void writepages_finish(struct ceph_osd_request *req)
 {
 	struct inode *inode = req->r_inode;
 	struct ceph_inode_info *ci = ceph_inode(inode);
diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 52e4b72..e75fd0b 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -616,8 +616,7 @@
 	kfree(aio_req);
 }
 
-static void ceph_aio_complete_req(struct ceph_osd_request *req,
-				  struct ceph_msg *msg)
+static void ceph_aio_complete_req(struct ceph_osd_request *req)
 {
 	int rc = req->r_result;
 	struct inode *inode = req->r_inode;
@@ -740,7 +739,7 @@
 out:
 	if (ret < 0) {
 		req->r_result = ret;
-		ceph_aio_complete_req(req, NULL);
+		ceph_aio_complete_req(req);
 	}
 
 	ceph_put_snap_context(snapc);
@@ -961,7 +960,7 @@
 							      req, false);
 			if (ret < 0) {
 				req->r_result = ret;
-				ceph_aio_complete_req(req, NULL);
+				ceph_aio_complete_req(req);
 			}
 		}
 		return -EIOCBQUEUED;