libceph: change ceph_con_in_msg_alloc convention to be less weird

(cherry picked from commit 4740a623d20c51d167da7f752b63e2b8714b2543)

This function's calling convention is very limiting.  In particular,
we can't return any error other than ENOMEM (and only implicitly),
which is a problem (see next patch).

Instead, return an normal 0 or error code, and make the skip a pointer
output parameter.  Drop the useless in_hdr argument (we have the con
pointer).

Signed-off-by: Sage Weil <sage@inktank.com>
Reviewed-by: Alex Elder <elder@inktank.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 31 insertions, 25 deletions

diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index c2f0ca36f4ab..bfd0878c5c4e 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -1733,9 +1733,7 @@ static int read_partial_message_section(struct ceph_connection *con,
 	return 1;
 }
 
-static bool ceph_con_in_msg_alloc(struct ceph_connection *con,
-				struct ceph_msg_header *hdr);
-
+static int ceph_con_in_msg_alloc(struct ceph_connection *con, int *skip);
 
 static int read_partial_message_pages(struct ceph_connection *con,
 				      struct page **pages,
@@ -1864,9 +1862,14 @@ static int read_partial_message(struct ceph_connection *con)
 
 	/* allocate message? */
 	if (!con->in_msg) {
+		int skip = 0;
+
 		dout("got hdr type %d front %d data %d\n", con->in_hdr.type,
 		     con->in_hdr.front_len, con->in_hdr.data_len);
-		if (ceph_con_in_msg_alloc(con, &con->in_hdr)) {
+		ret = ceph_con_in_msg_alloc(con, &skip);
+		if (ret < 0)
+			return ret;
+		if (skip) {
 			/* skip this message */
 			dout("alloc_msg said skip message\n");
 			BUG_ON(con->in_msg);
@@ -1876,12 +1879,8 @@ static int read_partial_message(struct ceph_connection *con)
 			con->in_seq++;
 			return 0;
 		}
-		if (!con->in_msg) {
-			con->error_msg =
-				"error allocating memory for incoming message";
-			return -ENOMEM;
-		}
 
+		BUG_ON(!con->in_msg);
 		BUG_ON(con->in_msg->con != con);
 		m = con->in_msg;
 		m->front.iov_len = 0;    /* haven't read it yet */
@@ -2715,43 +2714,50 @@ static int ceph_alloc_middle(struct ceph_connection *con, struct ceph_msg *msg)
  * connection, and save the result in con->in_msg.  Uses the
  * connection's private alloc_msg op if available.
  *
- * Returns true if the message should be skipped, false otherwise.
- * If true is returned (skip message), con->in_msg will be NULL.
- * If false is returned, con->in_msg will contain a pointer to the
- * newly-allocated message, or NULL in case of memory exhaustion.
+ * Returns 0 on success, or a negative error code.
+ *
+ * On success, if we set *skip = 1:
+ *  - the next message should be skipped and ignored.
+ *  - con->in_msg == NULL
+ * or if we set *skip = 0:
+ *  - con->in_msg is non-null.
+ * On error (ENOMEM, EAGAIN, ...),
+ *  - con->in_msg == NULL
  */
-static bool ceph_con_in_msg_alloc(struct ceph_connection *con,
-				struct ceph_msg_header *hdr)
+static int ceph_con_in_msg_alloc(struct ceph_connection *con, int *skip)
 {
+	struct ceph_msg_header *hdr = &con->in_hdr;
 	int type = le16_to_cpu(hdr->type);
 	int front_len = le32_to_cpu(hdr->front_len);
 	int middle_len = le32_to_cpu(hdr->middle_len);
-	int ret;
+	int ret = 0;
 
 	BUG_ON(con->in_msg != NULL);
 
 	if (con->ops->alloc_msg) {
-		int skip = 0;
-
 		mutex_unlock(&con->mutex);
-		con->in_msg = con->ops->alloc_msg(con, hdr, &skip);
+		con->in_msg = con->ops->alloc_msg(con, hdr, skip);
 		mutex_lock(&con->mutex);
 		if (con->in_msg) {
 			con->in_msg->con = con->ops->get(con);
 			BUG_ON(con->in_msg->con == NULL);
 		}
-		if (skip)
+		if (*skip) {
 			con->in_msg = NULL;
-
-		if (!con->in_msg)
-			return skip != 0;
+			return 0;
+		}
+		if (!con->in_msg) {
+			con->error_msg =
+				"error allocating memory for incoming message";
+			return -ENOMEM;
+		}
 	}
 	if (!con->in_msg) {
 		con->in_msg = ceph_msg_new(type, front_len, GFP_NOFS, false);
 		if (!con->in_msg) {
 			pr_err("unable to allocate msg type %d len %d\n",
 			       type, front_len);
-			return false;
+			return -ENOMEM;
 		}
 		con->in_msg->con = con->ops->get(con);
 		BUG_ON(con->in_msg->con == NULL);
@@ -2767,7 +2773,7 @@ static bool ceph_con_in_msg_alloc(struct ceph_connection *con,
 		}
 	}
 
-	return false;
+	return ret;
 }