mirror of https://gitee.com/openkylin/linux.git
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>
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@ -2819,18 +2819,21 @@ static int ceph_con_in_msg_alloc(struct ceph_connection *con, int *skip)
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ceph_msg_put(msg);
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return -EAGAIN;
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}
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con->in_msg = msg;
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if (con->in_msg) {
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if (msg) {
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BUG_ON(*skip);
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con->in_msg = msg;
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con->in_msg->con = con->ops->get(con);
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BUG_ON(con->in_msg->con == NULL);
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}
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if (*skip) {
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con->in_msg = NULL;
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return 0;
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}
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if (!con->in_msg) {
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con->error_msg =
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"error allocating memory for incoming message";
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} else {
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/*
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* Null message pointer means either we should skip
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* this message or we couldn't allocate memory. The
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* former is not an error.
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*/
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if (*skip)
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return 0;
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con->error_msg = "error allocating memory for incoming message";
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return -ENOMEM;
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}
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memcpy(&con->in_msg->hdr, &con->in_hdr, sizeof(con->in_hdr));
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