libceph: tweak ceph_alloc_msg()

(cherry picked from commit 1c20f2d26795803fc4f5155fe4fca5717a5944b6)

The function ceph_alloc_msg() is only used to allocate a message
that will be assigned to a connection's in_msg pointer.  Rename the
function so this implied usage is more clear.

In addition, make that assignment inside the function (again, since
that's precisely what it's intended to be used for).  This allows us
to return what is now provided via the passed-in address of a "skip"
variable.  The return type is now Boolean to be explicit that there
are only two possible outcomes.

Make sure the result of an ->alloc_msg method call always sets the
value of *skip properly.

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

3 files changed, 38 insertions, 27 deletions

diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index 6e21e609d791..31e8a15fa28c 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -1659,9 +1659,8 @@ static int read_partial_message_section(struct ceph_connection *con,
 	return 1;
 }
 
-static struct ceph_msg *ceph_alloc_msg(struct ceph_connection *con,
-				struct ceph_msg_header *hdr,
-				int *skip);
+static bool ceph_con_in_msg_alloc(struct ceph_connection *con,
+				struct ceph_msg_header *hdr);
 
 
 static int read_partial_message_pages(struct ceph_connection *con,
@@ -1744,7 +1743,6 @@ static int read_partial_message(struct ceph_connection *con)
 	int ret;
 	unsigned front_len, middle_len, data_len;
 	bool do_datacrc = !con->msgr->nocrc;
-	int skip;
 	u64 seq;
 	u32 crc;
 
@@ -1797,9 +1795,7 @@ static int read_partial_message(struct ceph_connection *con)
 	if (!con->in_msg) {
 		dout("got hdr type %d front %d data %d\n", con->in_hdr.type,
 		     con->in_hdr.front_len, con->in_hdr.data_len);
-		skip = 0;
-		con->in_msg = ceph_alloc_msg(con, &con->in_hdr, &skip);
-		if (skip) {
+		if (ceph_con_in_msg_alloc(con, &con->in_hdr)) {
 			/* skip this message */
 			dout("alloc_msg said skip message\n");
 			BUG_ON(con->in_msg);
@@ -2581,46 +2577,57 @@ static int ceph_alloc_middle(struct ceph_connection *con, struct ceph_msg *msg)
 }
 
 /*
- * Generic message allocator, for incoming messages.
+ * Allocate a message for receiving an incoming message on a
+ * 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.
  */
-static struct ceph_msg *ceph_alloc_msg(struct ceph_connection *con,
-				struct ceph_msg_header *hdr,
-				int *skip)
+static bool ceph_con_in_msg_alloc(struct ceph_connection *con,
+				struct ceph_msg_header *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);
-	struct ceph_msg *msg = NULL;
 	int ret;
 
+	BUG_ON(con->in_msg != NULL);
+
 	if (con->ops->alloc_msg) {
+		int skip = 0;
+
 		mutex_unlock(&con->mutex);
-		msg = con->ops->alloc_msg(con, hdr, skip);
+		con->in_msg = con->ops->alloc_msg(con, hdr, &skip);
 		mutex_lock(&con->mutex);
-		if (!msg || *skip)
-			return NULL;
+		if (skip)
+			con->in_msg = NULL;
+
+		if (!con->in_msg)
+			return skip != 0;
 	}
-	if (!msg) {
-		*skip = 0;
-		msg = ceph_msg_new(type, front_len, GFP_NOFS, false);
-		if (!msg) {
+	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 NULL;
+			return false;
 		}
-		msg->page_alignment = le16_to_cpu(hdr->data_off);
+		con->in_msg->page_alignment = le16_to_cpu(hdr->data_off);
 	}
-	memcpy(&msg->hdr, &con->in_hdr, sizeof(con->in_hdr));
+	memcpy(&con->in_msg->hdr, &con->in_hdr, sizeof(con->in_hdr));
 
-	if (middle_len && !msg->middle) {
-		ret = ceph_alloc_middle(con, msg);
+	if (middle_len && !con->in_msg->middle) {
+		ret = ceph_alloc_middle(con, con->in_msg);
 		if (ret < 0) {
-			ceph_msg_put(msg);
-			return NULL;
+			ceph_msg_put(con->in_msg);
+			con->in_msg = NULL;
 		}
 	}
 
-	return msg;
+	return false;
 }
 
 
diff --git a/net/ceph/mon_client.c b/net/ceph/mon_client.c
index d3c22b7218c8..674f191341a7 100644
--- a/net/ceph/mon_client.c
+++ b/net/ceph/mon_client.c
@@ -442,6 +442,7 @@ static struct ceph_msg *get_generic_reply(struct ceph_connection *con,
 		m = NULL;
 	} else {
 		dout("get_generic_reply %lld got %p\n", tid, req->reply);
+		*skip = 0;
 		m = ceph_msg_get(req->reply);
 		/*
 		 * we don't need to track the connection reading into
@@ -990,6 +991,8 @@ static struct ceph_msg *mon_alloc_msg(struct ceph_connection *con,
 	case CEPH_MSG_MDS_MAP:
 	case CEPH_MSG_OSD_MAP:
 		m = ceph_msg_new(type, front_len, GFP_NOFS, false);
+		if (!m)
+			return NULL;	/* ENOMEM--return skip == 0 */
 		break;
 	}
 
diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
index 448c9da8beff..24b427b1eca4 100644
--- a/net/ceph/osd_client.c
+++ b/net/ceph/osd_client.c
@@ -2077,6 +2077,7 @@ static struct ceph_msg *alloc_msg(struct ceph_connection *con,
 	int type = le16_to_cpu(hdr->type);
 	int front = le32_to_cpu(hdr->front_len);
 
+	*skip = 0;
 	switch (type) {
 	case CEPH_MSG_OSD_MAP:
 	case CEPH_MSG_WATCH_NOTIFY: