From: Benjamin LaHaise <bcrl@kvack.org>
Date: Sat, 21 Dec 2013 22:56:08 +0000 (-0500)
Subject: aio/migratepages: make aio migrate pages sane
X-Git-Tag: v3.13-rc5~4^2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8e321fefb0e60bae4e2a28d20fc4fa30758d27c6;p=pandora-kernel.git

aio/migratepages: make aio migrate pages sane

The arbitrary restriction on page counts offered by the core
migrate_page_move_mapping() code results in rather suspicious looking
fiddling with page reference counts in the aio_migratepage() operation.
To fix this, make migrate_page_move_mapping() take an extra_count parameter
that allows aio to tell the code about its own reference count on the page
being migrated.

While cleaning up aio_migratepage(), make it validate that the old page
being passed in is actually what aio_migratepage() expects to prevent
misbehaviour in the case of races.

Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>
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