libceph: change ceph_con_in_msg_alloc convention to be less weird

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>

diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index c3b628c..13b549b 100644 (file)
--- 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;
 }