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con->out_msg must be cleared on Policy::stateful_server (!CEPH_MSG_CONNECT_LOSSY) faults. Not doing so botches the reconnection attempt, because after writing the banner the messenger moves on to writing the data section of that message (either from where it got interrupted by the connection reset or from the beginning) instead of writing struct ceph_msg_connect. This results in a bizarre error message because the server sends CEPH_MSGR_TAG_BADPROTOVER but we think we wrote struct ceph_msg_connect: libceph: mds0 (1)172.21.15.45:6828 socket error on write ceph: mds0 reconnect start libceph: mds0 (1)172.21.15.45:6829 socket closed (con state OPEN) libceph: mds0 (1)172.21.15.45:6829 protocol version mismatch, my 32 != server's 32 libceph: mds0 (1)172.21.15.45:6829 protocol version mismatch AFAICT this bug goes back to the dawn of the kernel client. The reason it survived for so long is that only MDS sessions are stateful and only two MDS messages have a data section: CEPH_MSG_CLIENT_RECONNECT (always, but reconnecting is rare) and CEPH_MSG_CLIENT_REQUEST (only when xattrs are involved). The connection has to get reset precisely when such message is being sent -- in this case it was the former. Cc: stable@vger.kernel.org Link: https://tracker.ceph.com/issues/47723 Signed-off-by: Ilya Dryomov <idryomov@gmail.com> Reviewed-by: Jeff Layton <jlayton@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.