From 12996fc38a2d760f3b30c9ceae26d0eeb92fe52d Mon Sep 17 00:00:00 2001
From: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Date: Wed, 9 Feb 2011 16:11:32 -0500
Subject: [PATCH] xen-gntdev: Avoid double-mapping memory

If an already-mapped area of the device was mapped into userspace a
second time, a hypercall was incorrectly made to remap the memory
again. Avoid the hypercall on later mmap calls, and fail the mmap call
if a writable mapping is attempted on a read-only range.

Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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