Patchwork SYSFS "errors"

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Submitter Borislav Petkov
Date Feb. 19, 2013, 1:50 p.m.
Message ID <20130219135056.GH26623@pd.tnic>
Download mbox | patch
Permalink /patch/221701/
State Not Applicable
Delegated to: David Miller
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Comments

Borislav Petkov - Feb. 19, 2013, 1:50 p.m.
On Tue, Feb 19, 2013 at 03:38:09PM +0200, Felipe Balbi wrote:
> because changing the permission will cause the same issue:

Actually, I take that back. Mauro's patch will already create the file
anyway:

	if (mci->set_sdram_scrub_rate || mci->get_sdram_scrub_rate)

Adjusting the permissions is simply the last missing piece to this patch
to make the interface to userspace 100% coherent.

--
From: Mauro Carvalho Chehab <mchehab@redhat.com>
Date: Tue, 19 Feb 2013 09:16:10 -0300
Subject: [PATCH] EDAC: only create sdram_scrub_rate where supported

Currently, sdram_scrub_rate sysfs node is created even if the device
doesn't support get/set the scub rate. Change the logic to only
create this device node when the operation is supported.

If only read or only write is supported, it will keep returning -ENODEV
just like before.

Reported-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
---
 drivers/edac/edac_mc_sysfs.c | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)
Hannes Reinecke - Feb. 19, 2013, 1:58 p.m.
On 02/19/2013 02:50 PM, Borislav Petkov wrote:
> On Tue, Feb 19, 2013 at 03:38:09PM +0200, Felipe Balbi wrote:
>> because changing the permission will cause the same issue:
>
> Actually, I take that back. Mauro's patch will already create the file
> anyway:
>
> 	if (mci->set_sdram_scrub_rate || mci->get_sdram_scrub_rate)
>
> Adjusting the permissions is simply the last missing piece to this patch
> to make the interface to userspace 100% coherent.
>
> --
> From: Mauro Carvalho Chehab <mchehab@redhat.com>
> Date: Tue, 19 Feb 2013 09:16:10 -0300
> Subject: [PATCH] EDAC: only create sdram_scrub_rate where supported
>
> Currently, sdram_scrub_rate sysfs node is created even if the device
> doesn't support get/set the scub rate. Change the logic to only
> create this device node when the operation is supported.
>
> If only read or only write is supported, it will keep returning -ENODEV
> just like before.
>
> Reported-by: Felipe Balbi <balbi@ti.com>
> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
> ---
>   drivers/edac/edac_mc_sysfs.c | 21 +++++++++++++++++++--
>   1 file changed, 19 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/edac/edac_mc_sysfs.c b/drivers/edac/edac_mc_sysfs.c
> index 0ca1ca71157f..5a788e60ff67 100644
> --- a/drivers/edac/edac_mc_sysfs.c
> +++ b/drivers/edac/edac_mc_sysfs.c
> @@ -7,7 +7,7 @@
>    *
>    * Written Doug Thompson <norsk5@xmission.com> www.softwarebitmaker.com
>    *
> - * (c) 2012 - Mauro Carvalho Chehab <mchehab@redhat.com>
> + * (c) 2012-2013 - Mauro Carvalho Chehab <mchehab@redhat.com>
>    *	The entire API were re-written, and ported to use struct device
>    *
>    */
> @@ -878,7 +878,6 @@ static struct attribute *mci_attrs[] = {
>   	&dev_attr_ce_noinfo_count.attr,
>   	&dev_attr_ue_count.attr,
>   	&dev_attr_ce_count.attr,
> -	&dev_attr_sdram_scrub_rate.attr,
>   	&dev_attr_max_location.attr,
>   	NULL
>   };
> @@ -1012,6 +1011,23 @@ int edac_create_sysfs_mci_device(struct mem_ctl_info *mci)
>   		return err;
>   	}
>
> +	if (mci->set_sdram_scrub_rate || mci->get_sdram_scrub_rate) {
> +		umode_t mode = 0;
> +
> +		if (mci->get_sdram_scrub_rate)
> +			mode = S_IRUGO;
> +
> +		if (mci->set_sdram_scrub_rate)
> +			mode |= S_IWUSR;
> +
> +		dev_attr_sdram_scrub_rate.attr.mode = mode;
> +
> +		err = device_create_file(&mci->dev, &dev_attr_sdram_scrub_rate);
> +		if (err) {
> +			edac_dbg(1, "failure: create sdram_scrub_rate\n");
> +			goto fail2;
> +		}
> +	}
>   	/*
>   	 * Create the dimm/rank devices
>   	 */
> @@ -1056,6 +1072,7 @@ fail:
>   			continue;
>   		device_unregister(&dimm->dev);
>   	}
> +fail2:
>   	device_unregister(&mci->dev);
>   	bus_unregister(&mci->bus);
>   	kfree(mci->bus.name);
>
And of course you all know that creating sysfs attributes via 
'device_create_file' opens all sort of funny race conditions, 
especially when checking these attributes from udev ...

Please consider adding a default attribute which return '-EINVAL' or 
somesuch when the function pointers are not set.
But _not_ adding it via device_create_file(). That's evil.

Cheers,

Hannes
Borislav Petkov - Feb. 19, 2013, 2:10 p.m.
On Tue, Feb 19, 2013 at 02:58:07PM +0100, Hannes Reinecke wrote:
> Please consider adding a default attribute which return '-EINVAL' or
> somesuch when the function pointers are not set. But _not_ adding it
> via device_create_file(). That's evil.

This is what we do now. We probably could add the permissions fiddling
out in the the code but remain using DEVICE_ATTR.

Thanks.
Mauro Carvalho Chehab - Feb. 19, 2013, 2:14 p.m.
Em Tue, 19 Feb 2013 14:58:07 +0100
Hannes Reinecke <hare@suse.de> escreveu:

> On 02/19/2013 02:50 PM, Borislav Petkov wrote:
> > On Tue, Feb 19, 2013 at 03:38:09PM +0200, Felipe Balbi wrote:
> >> because changing the permission will cause the same issue:
> >
> > Actually, I take that back. Mauro's patch will already create the file
> > anyway:
> >
> > 	if (mci->set_sdram_scrub_rate || mci->get_sdram_scrub_rate)
> >
> > Adjusting the permissions is simply the last missing piece to this patch
> > to make the interface to userspace 100% coherent.
> >
> > --
> > From: Mauro Carvalho Chehab <mchehab@redhat.com>
> > Date: Tue, 19 Feb 2013 09:16:10 -0300
> > Subject: [PATCH] EDAC: only create sdram_scrub_rate where supported
> >
> > Currently, sdram_scrub_rate sysfs node is created even if the device
> > doesn't support get/set the scub rate. Change the logic to only
> > create this device node when the operation is supported.
> >
> > If only read or only write is supported, it will keep returning -ENODEV
> > just like before.
> >
> > Reported-by: Felipe Balbi <balbi@ti.com>
> > Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
> > ---
> >   drivers/edac/edac_mc_sysfs.c | 21 +++++++++++++++++++--
> >   1 file changed, 19 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/edac/edac_mc_sysfs.c b/drivers/edac/edac_mc_sysfs.c
> > index 0ca1ca71157f..5a788e60ff67 100644
> > --- a/drivers/edac/edac_mc_sysfs.c
> > +++ b/drivers/edac/edac_mc_sysfs.c
> > @@ -7,7 +7,7 @@
> >    *
> >    * Written Doug Thompson <norsk5@xmission.com> www.softwarebitmaker.com
> >    *
> > - * (c) 2012 - Mauro Carvalho Chehab <mchehab@redhat.com>
> > + * (c) 2012-2013 - Mauro Carvalho Chehab <mchehab@redhat.com>
> >    *	The entire API were re-written, and ported to use struct device
> >    *
> >    */
> > @@ -878,7 +878,6 @@ static struct attribute *mci_attrs[] = {
> >   	&dev_attr_ce_noinfo_count.attr,
> >   	&dev_attr_ue_count.attr,
> >   	&dev_attr_ce_count.attr,
> > -	&dev_attr_sdram_scrub_rate.attr,
> >   	&dev_attr_max_location.attr,
> >   	NULL
> >   };
> > @@ -1012,6 +1011,23 @@ int edac_create_sysfs_mci_device(struct mem_ctl_info *mci)
> >   		return err;
> >   	}
> >
> > +	if (mci->set_sdram_scrub_rate || mci->get_sdram_scrub_rate) {
> > +		umode_t mode = 0;
> > +
> > +		if (mci->get_sdram_scrub_rate)
> > +			mode = S_IRUGO;
> > +
> > +		if (mci->set_sdram_scrub_rate)
> > +			mode |= S_IWUSR;
> > +
> > +		dev_attr_sdram_scrub_rate.attr.mode = mode;
> > +
> > +		err = device_create_file(&mci->dev, &dev_attr_sdram_scrub_rate);
> > +		if (err) {
> > +			edac_dbg(1, "failure: create sdram_scrub_rate\n");
> > +			goto fail2;
> > +		}
> > +	}
> >   	/*
> >   	 * Create the dimm/rank devices
> >   	 */
> > @@ -1056,6 +1072,7 @@ fail:
> >   			continue;
> >   		device_unregister(&dimm->dev);
> >   	}
> > +fail2:
> >   	device_unregister(&mci->dev);
> >   	bus_unregister(&mci->bus);
> >   	kfree(mci->bus.name);
> >
> And of course you all know that creating sysfs attributes via 
> 'device_create_file' opens all sort of funny race conditions, 
> especially when checking these attributes from udev ...

Yes, we know that, but this subsystem has already lots of other
attributes created via device_create_file(). It used to be a
lot worse than that, as, on a very recent past (before Kernel 3.5),
those attributes were created via sysfs_create_file().

There's not much that can be done to avoid it on this subsystem.

> 
> Please consider adding a default attribute which return '-EINVAL' or 
> somesuch when the function pointers are not set.
> But _not_ adding it via device_create_file(). That's evil.

This thread started with Felipe's complain about it returning -ENOSYS ;)
when this feature is not supported.

Regards,
Mauro
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Felipe Balbi - Feb. 19, 2013, 2:19 p.m.
Hi,

On Tue, Feb 19, 2013 at 11:14:40AM -0300, Mauro Carvalho Chehab wrote:
> > Please consider adding a default attribute which return '-EINVAL' or 
> > somesuch when the function pointers are not set.
> > But _not_ adding it via device_create_file(). That's evil.
> 
> This thread started with Felipe's complain about it returning -ENOSYS ;)
> when this feature is not supported.

I was complaining about a file with read permission not being really
readable which is a fair bug IMHO.

Patch

diff --git a/drivers/edac/edac_mc_sysfs.c b/drivers/edac/edac_mc_sysfs.c
index 0ca1ca71157f..5a788e60ff67 100644
--- a/drivers/edac/edac_mc_sysfs.c
+++ b/drivers/edac/edac_mc_sysfs.c
@@ -7,7 +7,7 @@ 
  *
  * Written Doug Thompson <norsk5@xmission.com> www.softwarebitmaker.com
  *
- * (c) 2012 - Mauro Carvalho Chehab <mchehab@redhat.com>
+ * (c) 2012-2013 - Mauro Carvalho Chehab <mchehab@redhat.com>
  *	The entire API were re-written, and ported to use struct device
  *
  */
@@ -878,7 +878,6 @@  static struct attribute *mci_attrs[] = {
 	&dev_attr_ce_noinfo_count.attr,
 	&dev_attr_ue_count.attr,
 	&dev_attr_ce_count.attr,
-	&dev_attr_sdram_scrub_rate.attr,
 	&dev_attr_max_location.attr,
 	NULL
 };
@@ -1012,6 +1011,23 @@  int edac_create_sysfs_mci_device(struct mem_ctl_info *mci)
 		return err;
 	}
 
+	if (mci->set_sdram_scrub_rate || mci->get_sdram_scrub_rate) {
+		umode_t mode = 0;
+
+		if (mci->get_sdram_scrub_rate)
+			mode = S_IRUGO;
+
+		if (mci->set_sdram_scrub_rate)
+			mode |= S_IWUSR;
+
+		dev_attr_sdram_scrub_rate.attr.mode = mode;
+
+		err = device_create_file(&mci->dev, &dev_attr_sdram_scrub_rate);
+		if (err) {
+			edac_dbg(1, "failure: create sdram_scrub_rate\n");
+			goto fail2;
+		}
+	}
 	/*
 	 * Create the dimm/rank devices
 	 */
@@ -1056,6 +1072,7 @@  fail:
 			continue;
 		device_unregister(&dimm->dev);
 	}
+fail2:
 	device_unregister(&mci->dev);
 	bus_unregister(&mci->bus);
 	kfree(mci->bus.name);