On Fri, Dec 15, 2023 at 06:33:58AM +0000, Verma, Vishal L wrote:
> On Fri, 2023-12-15 at 05:56 +0000, Matthew Wilcox wrote:
> > On Thu, Dec 14, 2023 at 10:25:27PM -0700, Vishal Verma wrote:
> > > @@ -294,13 +294,10 @@ static ssize_t available_size_show(struct device *dev,
> > > struct device_attribute *attr, char *buf)
> > > {
> > > struct dax_region *dax_region = dev_get_drvdata(dev);
> > > - unsigned long long size;
> > >
> > > - device_lock(dev);
> > > - size = dax_region_avail_size(dax_region);
> > > - device_unlock(dev);
> > > + guard(device)(dev);
> > >
> > > - return sprintf(buf, "%llu\n", size);
> > > + return sprintf(buf, "%llu\n", dax_region_avail_size(dax_region));
> > > }
> >
> > Is this an appropriate use of guard()? sprintf is not the fastest of
> > functions, so we will end up holding the device_lock for longer than
> > we used to.
>
> Hi Matthew,
>
> Agreed that we end up holding the lock for a bit longer in many of
> these. I'm inclined to say this is okay, since these are all user
> configuration paths through sysfs, not affecting any sort of runtime
> performance.
Why does the lock have to be taken at all? You have a valid reference,
isn't that all you need?
thanks,
greg k-h
