On Wed, Sep 03, 2014 at 04:00:39PM -0400, Theodore Ts'o wrote:
> On Wed, Sep 03, 2014 at 05:31:22PM +0200, Jan Kara wrote:
> > Also one question:
> >
> > > - if (ei == locked_ei || !write_trylock(&ei->i_es_lock)) {
> > > - nr_skipped++;
> > > - spin_lock(&sbi->s_es_lock);
> > > __ext4_es_list_add(sbi, ei);
> > > + if (spin_is_contended(&sbi->s_es_lock)) {
> > > + spin_unlock(&sbi->s_es_lock);
> > > + spin_lock(&sbi->s_es_lock);
> > > + }
> > Why not cond_resched_lock(&sbi->s_es_lock)?
>
> I didn't think we were allowed to reschedule or sleep while in
> shrinker context?
You are allowed to block shrinkers if there is no possibility of
deadlock. i.e. that's what the __GFP_FS flag check in filesystem
shrinkers is for - so that they only run in GFP_KERNEL context
and not GFP_NOFS/GFP_NOIO/GFP_ATOMIC context where blocking reclaim
can cause deadlocks...
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
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