Re: [PATCH] zram: drop slot trylock and miss_free

[Sergey Senozhatsky]

On (26/02/10 14:29), Matthew Wilcox wrote:
> On Tue, Feb 10, 2026 at 12:50:37PM +0900, Sergey Senozhatsky wrote:
> > @@ -1943,15 +1927,9 @@ static ssize_t debug_stat_show(struct device *dev,
> >  {
> >  	int version = 1;
> >  	struct zram *zram = dev_to_zram(dev);
> > -	ssize_t ret;
> >  
> >  	guard(rwsem_read)(&zram->dev_lock);
> > -	ret = sysfs_emit(buf,
> > -			"version: %d\n0 %8llu\n",
> > -			version,
> > -			(u64)atomic64_read(&zram->stats.miss_free));
> > -
> > -	return ret;
> > +	return sysfs_emit(buf, "version: %d\n0 0\n", version);
> >  }
> 
> You don't need the dev_lock any more to just report the version.

True.  I'll think if I want to send out a v2 with just miss_free
removal.  The objective was to remove trylock (and all the things
around it), but trylock has to stay.  While we cannot have

	slot_lock(42)
	<IRQ>
	slot_lock(42)

any more, the slot-free-notify is still called under spin_lock, and
slot_lock() might_sleep().  So trylock has to stay around.

> And should the version be changed now that you've changed the format to
> not include miss_free?

The idea was to bump the version only when the format changes.  You
normally (well, technically "always", since e914d8f00391) would see
0 miss_free, and with the patch it's just a hard-coded 0.

Thanks for taking a look, Matthew.