ceph: harden send_mds_reconnect and handle active-MDS peer reset

Change send_mds_reconnect() to return an error code so callers can detect
and report reconnect failures instead of silently ignoring them. Add early
bailout checks for sessions that are already closed, rejected, or
unregistered, which avoids sending reconnect messages for sessions that
can no longer be recovered.

The early -ESTALE and -ENOENT bailouts use a separate fail_return label
that skips the pr_err_client diagnostic, since these codes indicate
expected concurrent-teardown races rather than genuine reconnect build
failures.

Move the "reconnect start" log after the early-bailout checks so it
only appears for sessions that actually proceed with reconnect.

Save the prior session state before transitioning to RECONNECTING,
and restore it in the failure path.  Without this, a transient
build or encoding failure (-ENOMEM, -ENOSPC) strands the session
in RECONNECTING indefinitely because check_new_map() only retries
sessions in RESTARTING state.

Rewrite mds_peer_reset() to handle the case where the MDS is past its
RECONNECT phase (i.e. active). An active MDS rejects CLIENT_RECONNECT
messages because it only accepts them during its own RECONNECT window
after restart. Previously, the client would send a doomed reconnect
that the MDS would reject or ignore. Now, the client tears the session
down locally and lets new requests re-open a fresh session, which is
the correct recovery for this scenario. The RECONNECTING state is
handled on the same teardown path, since the MDS will reject reconnect
attempts from an active client regardless of the session's local state.

Add explicit cases for CLOSED and REJECTED session states in
mds_peer_reset() since these are terminal states where a connection
drop is expected behavior.

The session teardown path in mds_peer_reset() follows the established
drop-and-reacquire locking pattern from check_new_map(): take
mdsc->mutex for session unregistration, release it, then take s->s_mutex
separately for cleanup. This avoids introducing a new simultaneous lock
nesting pattern.

Log reconnect failures from check_new_map() and mds_peer_reset() at
pr_warn level rather than pr_err, since return codes like -ESTALE
(closed/rejected session) and -ENOENT (unregistered session) are
expected during concurrent teardown. Log dropped messages for
unregistered sessions via doutc() (dynamic debug) rather than
pr_info, as post-reset message arrival is routine and does not
warrant unconditional logging.

Signed-off-by: Alex Markuze <amarkuze@redhat.com>
Reviewed-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>
Signed-off-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

0 files changed, 0 insertions, 0 deletions