From: "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>
To: "Verma, Vishal L" <vishal.l.verma@intel.com>
Cc: "willy@infradead.org" <willy@infradead.org>,
"david@redhat.com" <david@redhat.com>,
"joao.m.martins@oracle.com" <joao.m.martins@oracle.com>,
"Jiang, Dave" <dave.jiang@intel.com>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"osalvador@suse.de" <osalvador@suse.de>,
"linux-cxl@vger.kernel.org" <linux-cxl@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Williams, Dan J" <dan.j.williams@intel.com>,
"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
"Huang, Ying" <ying.huang@intel.com>,
"nvdimm@lists.linux.dev" <nvdimm@lists.linux.dev>,
"linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: Re: [PATCH v6 2/4] dax/bus: Use guard(device) in sysfs attribute helpers
Date: Fri, 15 Dec 2023 17:14:07 +0100 [thread overview]
Message-ID: <2023121547-goldfish-snowplow-345f@gregkh> (raw)
In-Reply-To: <d3eef0c19e949825ad0990a03eb55cc5f3033720.camel@intel.com>
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
next prev parent reply other threads:[~2023-12-15 16:14 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-15 5:25 [PATCH v6 0/4] Add DAX ABI for memmap_on_memory Vishal Verma
2023-12-15 5:25 ` [PATCH v6 1/4] Documentatiion/ABI: Add ABI documentation for sys-bus-dax Vishal Verma
2023-12-15 5:25 ` [PATCH v6 2/4] dax/bus: Use guard(device) in sysfs attribute helpers Vishal Verma
2023-12-15 5:56 ` Matthew Wilcox
2023-12-15 6:33 ` Verma, Vishal L
2023-12-15 16:14 ` gregkh [this message]
2023-12-15 7:27 ` Greg Kroah-Hartman
2023-12-15 17:15 ` Dan Williams
2023-12-15 17:32 ` Verma, Vishal L
2023-12-15 17:53 ` gregkh
2023-12-19 15:27 ` Jonathan Cameron
2023-12-15 5:25 ` [PATCH v6 3/4] mm/memory_hotplug: export mhp_supports_memmap_on_memory() Vishal Verma
2023-12-15 5:25 ` [PATCH v6 4/4] dax: add a sysfs knob to control memmap_on_memory behavior Vishal Verma
2023-12-15 7:53 ` Huang, Ying
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