From: Dmitry <dmonakhov@openvz.org>
Date: Sat, 9 Oct 2010 19:15:30 +0000 (+0400)
Subject: quota: fix dquot_disable vs dquot_transfer race v2
X-Git-Tag: v2.6.37-rc1~78^2~14
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9e32784b71c2c84895016ca6ab271591669c02aa;p=pandora-kernel.git

quota: fix dquot_disable vs dquot_transfer race v2

I've got following lockup:
dquot_disable                              dquot_transfer
                                            ->dqget()
					       sb_has_quota_active
dqopt->flags &= ~dquot_state_flag(f, cnt)      atomic_inc(dq->dq_count)
 ->drop_dquot_ref(sb, cnt);
    down_write(dqptr_sem)
    inode->i_dquot[cnt] = NULL              ->__dquot_transfer
invalidate_dquots(sb, cnt);		       down_write(&dqptr_sem)
  ->wait for dq_wait_unused		       inode->i_dquot = new_dquot
  /* wait forever */                            ^^^^New quota user^^^^^^

We cannot allow new references to dquots from inodes after drop_dquot_ref()
has removed them.  We have to recheck quota state under dqptr_sem and before
assignment, as we do it in dquot_initialize().

Signed-off-by: Dmitry Monakhov <dmonakhov@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
---

Reading git-diff-tree failed