From: Carlos Maiolino <cmaiolino@redhat.com>
Date: Thu, 20 Sep 2012 13:32:36 +0000 (-0300)
Subject: xfs: Fix m_agirotor reset during AG selection
X-Git-Tag: omap-for-v3.7-rc1/fixes-cpufreq-signed~35^2~5
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8aea3ff411b2ce8fe7b46644298ed243a920eb24;p=pandora-kernel.git

xfs: Fix m_agirotor reset during AG selection

xfs_ialloc_next_ag() currently resets m_agirotor when it is equal to
m_maxagi:

         if (++mp->m_agirotor == mp->m_maxagi)
	         mp->m_agirotor = 0;

But, if for some reason mp->m_maxagi changes to a lower value than
current m_agirotor, this condition will never be true, causing
m_agirotor to exceed the maximum allowed value (m_maxagi).

This implies mainly during lookups for xfs_perag structs in its radix
tree, since the agno value used for the lookup is based on m_agirotor.
An out-of-range m_agirotor may cause a lookup failure which in case will
return NULL.

As an example, the value of m_maxagi is decreased during
inode64->inode32 remount process, case where I've found this problem.

Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>
---

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