libceph: clean up skipped message logic
In ceph_con_in_msg_alloc() it is possible for a connection's
alloc_msg method to indicate an incoming message should be skipped.
By default, read_partial_message() initializes the skip variable
to 0 before it gets provided to ceph_con_in_msg_alloc().
The osd client, mon client, and mds client each supply an alloc_msg
method. The mds client always assigns skip to be 0.
The other two leave the skip value of as-is, or assigns it to zero,
except:
- if no (osd or mon) request having the given tid is found, in
which case skip is set to 1 and NULL is returned; or
- in the osd client, if the data of the reply message is not
adequate to hold the message to be read, it assigns skip
value 1 and returns NULL.
So the returned message pointer will always be NULL if skip is ever
non-zero.
Clean up the logic a bit in ceph_con_in_msg_alloc() to make this
state of affairs more obvious. Add a comment explaining how a null
message pointer can mean either a message that should be skipped or
a problem allocating a message.
This resolves:
http://tracker.ceph.com/issues/4324
Reported-by: Greg Farnum <greg@inktank.com>
Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Greg Farnum <greg@inktank.com>
diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index c7d4278..af0c35d 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -2819,18 +2819,21 @@
ceph_msg_put(msg);
return -EAGAIN;
}
- con->in_msg = msg;
- if (con->in_msg) {
+ if (msg) {
+ BUG_ON(*skip);
+ con->in_msg = msg;
con->in_msg->con = con->ops->get(con);
BUG_ON(con->in_msg->con == NULL);
- }
- if (*skip) {
- con->in_msg = NULL;
- return 0;
- }
- if (!con->in_msg) {
- con->error_msg =
- "error allocating memory for incoming message";
+ } else {
+ /*
+ * Null message pointer means either we should skip
+ * this message or we couldn't allocate memory. The
+ * former is not an error.
+ */
+ if (*skip)
+ return 0;
+ con->error_msg = "error allocating memory for incoming message";
+
return -ENOMEM;
}
memcpy(&con->in_msg->hdr, &con->in_hdr, sizeof(con->in_hdr));