From: Carlos Maiolino Date: Thu, 20 Sep 2012 13:32:36 +0000 (-0300) Subject: xfs: Fix m_agirotor reset during AG selection X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=8aea3ff411b2ce8fe7b46644298ed243a920eb24;p=linux-beck.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 Reviewed-by: Christoph Hellwig Reviewed-by: Mark Tinguely Signed-off-by: Ben Myers --- diff --git a/fs/xfs/xfs_ialloc.c b/fs/xfs/xfs_ialloc.c index 5aceb3f8ecd6..445bf1aef31c 100644 --- a/fs/xfs/xfs_ialloc.c +++ b/fs/xfs/xfs_ialloc.c @@ -431,7 +431,7 @@ xfs_ialloc_next_ag( spin_lock(&mp->m_agirotor_lock); agno = mp->m_agirotor; - if (++mp->m_agirotor == mp->m_maxagi) + if (++mp->m_agirotor >= mp->m_maxagi) mp->m_agirotor = 0; spin_unlock(&mp->m_agirotor_lock);