If a connection is closed and/or reopened (ceph_con_close, ceph_con_open)
it can race with a callback. con_work does various state checks for
closed or reopened sockets at the beginning, but drops con->mutex before
making callbacks. We need to check for state bit changes after retaking
the lock to ensure we restart con_work and execute those CLOSED/OPENING
tests or else we may end up operating under stale assumptions.
In Jim's case, this was causing 'bad tag' errors.
There are four cases where we re-take the con->mutex inside con_work: catch
them all and return EAGAIN from try_{read,write} so that we can restart
con_work.
Reported-by: Jim Schutt <jaschut@sandia.gov>
Tested-by: Jim Schutt <jaschut@sandia.gov>
Signed-off-by: Sage Weil <sage@newdream.net>
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