Re: [PATCH v3 2/3] zram: fix deadlock with sysfs attribute usage and driver removal

[Luis Chamberlain]

On Tue, Jun 22, 2021 at 09:41:23AM +0200, Greg KH wrote:
> On Mon, Jun 21, 2021 at 04:36:34PM -0700, Luis Chamberlain wrote:
> > +	ssize_t __ret; \
> > +	if (!try_module_get(THIS_MODULE)) \
> 
> try_module_get(THIS_MODULE) is always racy and probably does not do what
> you want it to do.  You always want to get/put module references from
> code that is NOT the code calling these functions.

In this case, we want it to trump module removal if it succeeds. That's all.

> > +		return -ENODEV; \
> > +	__ret = _name ## _store(dev, attr, buf, len); \
> > +	module_put(THIS_MODULE); \
> 
> This too is going to be racy.
> 
> While fun to poke at, I still think this is pointless.

If you have a better idea, which does not "DOS" module removal, please
let me know!

  Luis