From: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Date: Thu, 13 Dec 2007 14:15:25 +0000 (+0000)
Subject: dm: table detect io beyond device
X-Git-Tag: v2.6.24-rc6~4^2~5
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=512875bd9661368da6f993205a61213b79ba1df0;p=pandora-kernel.git

dm: table detect io beyond device

This patch fixes a panic on shrinking a DM device if there is
outstanding I/O to the part of the device that is being removed.
(Normally this doesn't happen - a filesystem would be resized first,
for example.)

The bug is that __clone_and_map() assumes dm_table_find_target()
always returns a valid pointer.  It may fail if a bio arrives from the
block layer but its target sector is no longer included in the DM
btree.

This patch appends an empty entry to table->targets[] which will
be returned by a lookup beyond the end of the device.

After calling dm_table_find_target(), __clone_and_map() and target_message()
check for this condition using
dm_target_is_valid().

Sample test script to trigger oops:
---

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