From: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Date: Thu, 12 Aug 2010 03:13:55 +0000 (+0100)
Subject: dm ioctl: release _hash_lock between devices in remove_all
X-Git-Tag: v2.6.36-rc1~51^2~25
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=98f332855effef02aeb738e4d62e9a5b903c52fd;p=pandora-kernel.git

dm ioctl: release _hash_lock between devices in remove_all

This patch changes dm_hash_remove_all() to release _hash_lock when
removing a device.  After removing the device, dm_hash_remove_all()
takes _hash_lock and searches the hash from scratch again.

This patch is a preparation for the next patch, which changes device
deletion code to wait for md reference to be 0.  Without this patch,
the wait in the next patch may cause AB-BA deadlock:
  CPU0                                CPU1
  -----------------------------------------------------------------------
  dm_hash_remove_all()
    down_write(_hash_lock)
                                      table_status()
                                        md = find_device()
                                               dm_get(md)
                                                 <increment md->holders>
                                        dm_get_live_or_inactive_table()
                                          dm_get_inactive_table()
                                            down_write(_hash_lock)
    <in the md deletion code>
      <wait for md->holders to be 0>

Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Cc: stable@kernel.org
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
---

Reading git-diff-tree failed