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>
diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index aad1316..ed14bee 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -1736,6 +1736,7 @@
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 @@
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 @@
* 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 @@
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);