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>
1 file changed