From 06c49f9fa31f026e00a15cc6487b4d8d99b0e333 Mon Sep 17 00:00:00 2001
From: Peter Hurley <peter@hurleysoftware.com>
Date: Fri, 16 Jan 2015 15:05:38 -0500
Subject: [PATCH] n_tty: Fix PARMRK over-throttling

If PARMRK is enabled, the available read buffer space computation is
overly-pessimistic, which results in severely throttled i/o, even
in the absence of parity errors. For example, if the 4k read buffer
contains 1k processed data, the input worker will compute available
space of 333 bytes, despite 3k being available. At 1365 chars of
processed data, 0 space available is computed.

*Divide remaining space* by 3, truncating down (if left == 2, left = 0).

Reported-by: Christian Riesch <christian.riesch@omicron.at>

Conflicts:
	drivers/tty/n_tty.c

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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