[Saucy][SRU][PATCH 0/2] xen-blkfront: revoke foreign access for grants not mapped

[Joseph Salisbury]

BugLink: http://bugs.launchpad.net/bugs/1319003

== Saucy SRU Justification ==
When used as a Xen guest, Ubuntu 13.10 may be slower than older releases in terms of storage performance. This is due to the persistent-grants feature introduced in xen-blkfront on the Linux Kernel 3.8 series. From 3.8 to 3.12 (inclusive), xen-blkfront will add an extra set of memcpy() operations regardless of persistent-grants support in the backend (i.e. xen-blkback, qemu, tapdisk).  This issue is fixed in mainline as of v3.13-rc1.  However, the fix was not cc'd to stable.  


== Fixes ==
commit fbe363c476afe8ec992d3baf682670a4bd1b6ce6
Author: Roger Pau Monne <roger.pau at citrix.com>
Date:   Mon Aug 12 12:53:44 2013 +0200

    xen-blkfront: revoke foreign access for grants not mapped by the backend

commit bfe11d6de1c416cea4f3f0f35f864162063ce3fa
Author: Roger Pau Monne <roger.pau at citrix.com>
Date:   Tue Oct 29 18:31:14 2013 +0100

    xen-blkfront: restore the non-persistent data path



== Test Case ==
A test kernel was built with this patch and tested by the original bug reporter.  The bug reporter states the test kernel resolved the bug.




Roger Pau Monne (2):
  xen-blkfront: revoke foreign access for grants not mapped by the
    backend
  xen-blkfront: restore the non-persistent data path

 drivers/block/xen-blkfront.c | 148 ++++++++++++++++++++++++++++++++++++-------
 1 file changed, 124 insertions(+), 24 deletions(-)

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2.0.0