The rpc server tries to ensure that there will be room to send a reply
before it receives a request.
It does this by tracking, in xpt_reserved, an upper bound on the total
size of the replies that is has already committed to for the socket.
Currently it is adding in the estimate for a new reply *before* it
checks whether there is space available. If it finds that there is not
space, it then subtracts the estimate back out.
This may lead the subsequent svc_xprt_enqueue to decide that there is
space after all.
The results is a svc_recv() that will repeatedly return -EAGAIN, causing
server threads to loop without doing any actual work.
Cc: stable@vger.kernel.org Reported-by: Michael Tokarev <mjt@tls.msk.ru> Tested-by: Michael Tokarev <mjt@tls.msk.ru> Signed-off-by: J. Bruce Fields <bfields@redhat.com>
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