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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>
This commit is contained in:
Dmitry 2010-10-09 23:15:30 +04:00 коммит произвёл Jan Kara
Родитель a910eefa51
Коммит 9e32784b71
1 изменённых файлов: 12 добавлений и 6 удалений
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18
fs/quota/dquot.c
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@ -1736,6 +1736,7 @@ int __dquot_transfer(struct inode *inode, struct dquot **transfer_to)
qsize_t rsv_space = 0;
struct dquot *transfer_from[MAXQUOTAS] = {};
int cnt, ret = 0;
char is_valid[MAXQUOTAS] = {};
char warntype_to[MAXQUOTAS];
char warntype_from_inodes[MAXQUOTAS], warntype_from_space[MAXQUOTAS];
@ -1757,8 +1758,15 @@ int __dquot_transfer(struct inode *inode, struct dquot **transfer_to)
space = cur_space + rsv_space;
/* Build the transfer_from list and check the limits */
for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
/*
* Skip changes for same uid or gid or for turned off quota-type.
*/
if (!transfer_to[cnt])
continue;
/* Avoid races with quotaoff() */
if (!sb_has_quota_active(inode->i_sb, cnt))
continue;
is_valid[cnt] = 1;
transfer_from[cnt] = inode->i_dquot[cnt];
ret = check_idq(transfer_to[cnt], 1, warntype_to + cnt);
if (ret)
@ -1772,12 +1780,8 @@ int __dquot_transfer(struct inode *inode, struct dquot **transfer_to)
* Finally perform the needed transfer from transfer_from to transfer_to
*/
for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
/*
* Skip changes for same uid or gid or for turned off quota-type.
*/
if (!transfer_to[cnt])
if (!is_valid[cnt])
continue;
/* Due to IO error we might not have transfer_from[] structure */
if (transfer_from[cnt]) {
warntype_from_inodes[cnt] =
@ -1803,7 +1807,9 @@ int __dquot_transfer(struct inode *inode, struct dquot **transfer_to)
mark_all_dquot_dirty(transfer_to);
/* Pass back references to put */
for (cnt = 0; cnt < MAXQUOTAS; cnt++)
transfer_to[cnt] = transfer_from[cnt];
if (is_valid[cnt])
transfer_to[cnt] = transfer_from[cnt];
warn:
flush_warnings(transfer_to, warntype_to);
flush_warnings(transfer_from, warntype_from_inodes);