From: "Verma, Vishal L" <vishal.l.verma@intel.com>
To: "willy@infradead.org" <willy@infradead.org>
Cc: "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>,
"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
"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 06:33:58 +0000 [thread overview]
Message-ID: <d3eef0c19e949825ad0990a03eb55cc5f3033720.camel@intel.com> (raw)
In-Reply-To: <ZXvqjIqvcGkumNXf@casper.infradead.org>
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.
>
> > @@ -908,9 +890,8 @@ static ssize_t size_show(struct device *dev,
> > struct dev_dax *dev_dax = to_dev_dax(dev);
> > unsigned long long size;
> >
> > - device_lock(dev);
> > + guard(device)(dev);
> > size = dev_dax_size(dev_dax);
> > - device_unlock(dev);
> >
> > return sprintf(buf, "%llu\n", size);
> > }
>
> If it is appropriate, then you can do without the 'size' variable here.
Yep will remove. I suppose a lot of these can also switch to sysfs_emit
as Greg pointed out in a previous posting. I can add that as a separate
cleanup patch.
>
> > @@ -1137,21 +1117,20 @@ static ssize_t mapping_store(struct device *dev, struct device_attribute *attr,
> > if (rc)
> > return rc;
> >
> > - rc = -ENXIO;
> > - device_lock(dax_region->dev);
> > - if (!dax_region->dev->driver) {
> > - device_unlock(dax_region->dev);
> > - return rc;
> > - }
> > - device_lock(dev);
> > + guard(device)(dax_region->dev);
> > + if (!dax_region->dev->driver)
> > + return -ENXIO;
> >
> > + guard(device)(dev);
> > to_alloc = range_len(&r);
> > - if (alloc_is_aligned(dev_dax, to_alloc))
> > - rc = alloc_dev_dax_range(dev_dax, r.start, to_alloc);
> > - device_unlock(dev);
> > - device_unlock(dax_region->dev);
> > + if (!alloc_is_aligned(dev_dax, to_alloc))
> > + return -ENXIO;
> >
> > - return rc == 0 ? len : rc;
> > + rc = alloc_dev_dax_range(dev_dax, r.start, to_alloc);
> > + if (rc)
> > + return rc;
> > +
> > + return len;
> > }
>
> Have I mentioned how much I hate the "rc" naming convention? It tells
> you nothing useful about the contents of the variable. If you called it
> 'err', I'd know it was an error, and then the end of this function would
> make sense.
>
> if (err)
> return err;
> return len;
>
I'm a little hesitant to change this because the 'rc' convention is
used all over this file, and while I don't mind making this change for
the bits I touch in this patch, it would just result in a mix of 'rc'
and 'err' in this file.
next prev parent reply other threads:[~2023-12-15 6:34 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 [this message]
2023-12-15 16:14 ` gregkh
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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