Jan Kara 1362f4ea20 quota: Fix race between dqput() and dquot_scan_active()
Currently last dqput() can race with dquot_scan_active() causing it to
call callback for an already deactivated dquot. The race is as follows:

CPU1					CPU2
  dqput()
    spin_lock(&dq_list_lock);
    if (atomic_read(&dquot->dq_count) > 1) {
     - not taken
    if (test_bit(DQ_ACTIVE_B, &dquot->dq_flags)) {
      spin_unlock(&dq_list_lock);
      ->release_dquot(dquot);
        if (atomic_read(&dquot->dq_count) > 1)
         - not taken
					  dquot_scan_active()
					    spin_lock(&dq_list_lock);
					    if (!test_bit(DQ_ACTIVE_B, &dquot->dq_flags))
					     - not taken
					    atomic_inc(&dquot->dq_count);
					    spin_unlock(&dq_list_lock);
        - proceeds to release dquot
					    ret = fn(dquot, priv);
					     - called for inactive dquot

Fix the problem by making sure possible ->release_dquot() is finished by
the time we call the callback and new calls to it will notice reference
dquot_scan_active() has taken and bail out.

CC: stable@vger.kernel.org # >= 2.6.29
Signed-off-by: Jan Kara <jack@suse.cz>
2014-02-20 21:57:04 +01:00
..
2013-10-24 23:43:27 -04:00
2014-01-25 03:13:02 -05:00
2014-01-25 03:13:02 -05:00
2014-01-23 18:54:14 +02:00
2013-06-29 12:56:53 +04:00
2014-01-26 11:51:09 +01:00
2014-02-02 16:24:07 -08:00
2013-12-04 12:27:46 +01:00
2013-12-08 21:14:59 -05:00
2014-01-28 18:56:37 -08:00
2014-02-08 10:50:58 -06:00
2013-09-16 18:20:25 -07:00
2014-02-10 16:01:42 -08:00
2014-02-11 13:48:11 -05:00
2014-01-25 03:14:05 -05:00
2013-06-29 12:56:32 +04:00
2014-01-25 03:13:03 -05:00
2013-06-29 12:56:39 +04:00
2013-12-22 11:03:49 -08:00
2013-12-05 16:36:21 -06:00
2013-06-29 12:57:04 +04:00
2013-10-24 23:34:54 -04:00
2013-09-13 23:06:40 -04:00
2013-06-29 12:57:05 +04:00
2014-01-26 12:37:55 -05:00
2013-11-23 22:33:47 -08:00
2013-09-10 18:56:31 -04:00
2013-10-24 23:34:54 -04:00
2013-11-09 00:16:20 -05:00
2013-10-24 23:34:54 -04:00
2014-01-26 08:26:40 -05:00
2013-11-23 22:33:47 -08:00
2013-10-24 23:35:00 -04:00
2013-10-24 23:34:54 -04:00
2014-01-22 19:36:57 +01:00
2013-11-09 00:16:31 -05:00