On Tue 27-12-11 10:51:00, Joel Becker wrote:
> On Thu, Dec 22, 2011 at 03:07:45PM +0100, Jan Kara wrote:
> > j_barrier mutex is used for serializing different journal lock operations. The
> > problem with it is that e.g. FIFREEZE ioctl results in process leaving kernel
> > with j_barrier mutex held which makes lockdep freak out. Also hibernation code
> > wants to freeze filesystem but it cannot do so because it then cannot hibernate
> > the system because of mutex being locked.
> >
> > So we remove j_barrier mutex and use direct wait on j_barrier_count instead.
> > Since locking journal is a rare operation we don't have to care about fairness
> > or such things.
> >
> > CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Jan Kara <jack@xxxxxxx>
>
> Strikes me as pretty reasonable.
>
> > void journal_lock_updates(journal_t *journal)
> > {
> > DEFINE_WAIT(wait);
> >
> > +wait:
> > + /* Wait for previous locked operation to finish */
> > + wait_event(journal->j_wait_transaction_locked,
> > + journal->j_barrier_count == 0);
> > +
> > spin_lock(&journal->j_state_lock);
> > + /*
> > + * Check reliably under the lock whether we are the ones winning the race
> > + * and locking the journal
> > + */
> > + if (journal->j_barrier_count > 0) {
> > + spin_unlock(&journal->j_state_lock);
> > + goto wait;
> > + }
>
> I suppose I'd prefer:
>
> do {
> wait_event(journal->j_wait_transaction_locked,
> journal->j_barrier_count == 0);
>
> spin_lock(&journal->j_state_lock);
> if (journal->j_barrier_count == 0)
> break;
> spin_unlock(&journal->j_state_lock);
> } while (1);
> ++journal->j_barrier_count;
>
> because I hate using goto for trivial loops, but that's a nitpick.
Frankly, I'm more used to parsing simple goto loops like mine than
infinite-loop + break statements in cases like this. So I'll take the
liberty of being a maintainer and keep the goto. But thanks for the
suggestion anyway.
> ACK.
Thanks for review!
Honza
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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