quota: Fix possible dq_flags corruption

quota: Fix possible dq_flags corruption

commit 08261673cb6dc638c39f44d69b76fffb57b92a8b upstream.

dq_flags are modified non-atomically in do_set_dqblk via __set_bit calls and
atomically for example in mark_dquot_dirty or clear_dquot_dirty.  Hence a
change done by an atomic operation can be overwritten by a change done by a
non-atomic one. Fix the problem by using atomic bitops even in do_set_dqblk.

Signed-off-by: Andrew Perepechko <andrew.perepechko@sun.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>