[PATCH] powerpc/papr_scm: Make 'perf_stats' invisible if perf-stats unavailable

In case performance stats for an nvdimm are not available, reading the
'perf_stats' sysfs file returns an -ENOENT error. A better approach is
to make the 'perf_stats' file entirely invisible to indicate that
performance stats for an nvdimm are unavailable.

So this patch updates 'papr_nd_attribute_group' to add a 'is_visible'
callback implemented as newly introduced 'papr_nd_attribute_visible()'
that returns an appropriate mode in case performance stats aren't
supported in a given nvdimm.

Also the initialization of 'papr_scm_priv.stat_buffer_len' is moved
from papr_scm_nvdimm_init() to papr_scm_probe() so that it value is
available when 'papr_nd_attribute_visible()' is called during nvdimm
initialization.

Fixes: 2d02bf835e57('powerpc/papr_scm: Fetch nvdimm performance stats from PHYP')
Signed-off-by: Vaibhav Jain <redacted>
---
 arch/powerpc/platforms/pseries/papr_scm.c | 37 ++++++++++++++++-------
 1 file changed, 26 insertions(+), 11 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
index 12f1513f0fca..90f0af8fefe8 100644
--- a/arch/powerpc/platforms/pseries/papr_scm.c
+++ b/arch/powerpc/platforms/pseries/papr_scm.c

@@ -907,6 +907,20 @@ static ssize_t flags_show(struct device *dev,
 }
 DEVICE_ATTR_RO(flags);
 
+umode_t papr_nd_attribute_visible(struct kobject *kobj, struct attribute *attr,
+				  int n)
+{
+	struct device *dev = container_of(kobj, typeof(*dev), kobj);
+	struct nvdimm *nvdimm = to_nvdimm(dev);
+	struct papr_scm_priv *p = nvdimm_provider_data(nvdimm);
+
+	/* For if perf-stats not available remove perf_stats sysfs */
+	if (attr == &dev_attr_perf_stats.attr && p->stat_buffer_len == 0)
+		return 0;
+
+	return attr->mode;
+}
+
 /* papr_scm specific dimm attributes */
 static struct attribute *papr_nd_attributes[] = {
 	&dev_attr_flags.attr,

@@ -916,6 +930,7 @@ static struct attribute *papr_nd_attributes[] = {
 
 static struct attribute_group papr_nd_attribute_group = {
 	.name = "papr",
+	.is_visible = papr_nd_attribute_visible,
 	.attrs = papr_nd_attributes,
 };
 

@@ -931,7 +946,6 @@ static int papr_scm_nvdimm_init(struct papr_scm_priv *p)
 	struct nd_region_desc ndr_desc;
 	unsigned long dimm_flags;
 	int target_nid, online_nid;
-	ssize_t stat_size;
 
 	p->bus_desc.ndctl = papr_scm_ndctl;
 	p->bus_desc.module = THIS_MODULE;

@@ -1016,16 +1030,6 @@ static int papr_scm_nvdimm_init(struct papr_scm_priv *p)
 	list_add_tail(&p->region_list, &papr_nd_regions);
 	mutex_unlock(&papr_ndr_lock);
 
-	/* Try retriving the stat buffer and see if its supported */
-	stat_size = drc_pmem_query_stats(p, NULL, 0);
-	if (stat_size > 0) {
-		p->stat_buffer_len = stat_size;
-		dev_dbg(&p->pdev->dev, "Max perf-stat size %lu-bytes\n",
-			p->stat_buffer_len);
-	} else {
-		dev_info(&p->pdev->dev, "Dimm performance stats unavailable\n");
-	}
-
 	return 0;
 
 err:	nvdimm_bus_unregister(p->bus);

@@ -1102,6 +1106,7 @@ static int papr_scm_probe(struct platform_device *pdev)
 	u64 blocks, block_size;
 	struct papr_scm_priv *p;
 	const char *uuid_str;
+	ssize_t stat_size;
 	u64 uuid[2];
 	int rc;
 

@@ -1179,6 +1184,16 @@ static int papr_scm_probe(struct platform_device *pdev)
 	p->res.name  = pdev->name;
 	p->res.flags = IORESOURCE_MEM;
 
+	/* Try retriving the stat buffer and see if its supported */
+	stat_size = drc_pmem_query_stats(p, NULL, 0);
+	if (stat_size > 0) {
+		p->stat_buffer_len = stat_size;
+		dev_dbg(&p->pdev->dev, "Max perf-stat size %lu-bytes\n",
+			p->stat_buffer_len);
+	} else {
+		dev_info(&p->pdev->dev, "Dimm performance stats unavailable\n");
+	}
+
 	rc = papr_scm_nvdimm_init(p);
 	if (rc)
 		goto err2;

-- 
2.31.1

Hi Vaibhav,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on powerpc/next]
[also build test WARNING on v5.12 next-20210505]
[cannot apply to scottwood/next mpe/next]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Vaibhav-Jain/powerpc-papr_scm-Make-perf_stats-invisible-if-perf-stats-unavailable/20210506-031853
base:   https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git next
config: powerpc-allyesconfig (attached as .config)
compiler: powerpc64-linux-gcc (GCC) 9.3.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/0day-ci/linux/commit/8e7ce04ec36dea95fad178585b697a9c5b5c259d
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Vaibhav-Jain/powerpc-papr_scm-Make-perf_stats-invisible-if-perf-stats-unavailable/20210506-031853
        git checkout 8e7ce04ec36dea95fad178585b697a9c5b5c259d
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross W=1 ARCH=powerpc 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <redacted>

All warnings (new ones prefixed by >>):

quoted

arch/powerpc/platforms/pseries/papr_scm.c:903:9: warning: no previous prototype for 'papr_nd_attribute_visible' [-Wmissing-prototypes]

     903 | umode_t papr_nd_attribute_visible(struct kobject *kobj, struct attribute *attr,
         |         ^~~~~~~~~~~~~~~~~~~~~~~~~


vim +/papr_nd_attribute_visible +903 arch/powerpc/platforms/pseries/papr_scm.c

   902	
 > 903	umode_t papr_nd_attribute_visible(struct kobject *kobj, struct attribute *attr,
   904					  int n)
   905	{
   906		struct device *dev = container_of(kobj, typeof(*dev), kobj);
   907		struct nvdimm *nvdimm = to_nvdimm(dev);
   908		struct papr_scm_priv *p = nvdimm_provider_data(nvdimm);
   909	
   910		/* For if perf-stats not available remove perf_stats sysfs */
   911		if (attr == &dev_attr_perf_stats.attr && p->stat_buffer_len == 0)
   912			return 0;
   913	
   914		return attr->mode;
   915	}
   916	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

Vaibhav Jain [off-list ref] writes:

With this patch https://lore.kernel.org/linuxppc-dev/20210505191606.51666-1-vaibhav@linux.ibm.com
We are adding details of whyy performance stat query hcall failed. Do we
need to print again here?  Are we being more verbose here?

-aneesh

"Aneesh Kumar K.V" [off-list ref] writes:

Vaibhav Jain [off-list ref] writes:

quoted

In case performance stats for an nvdimm are not available, reading the
'perf_stats' sysfs file returns an -ENOENT error. A better approach is
to make the 'perf_stats' file entirely invisible to indicate that
performance stats for an nvdimm are unavailable.

So this patch updates 'papr_nd_attribute_group' to add a 'is_visible'
callback implemented as newly introduced 'papr_nd_attribute_visible()'
that returns an appropriate mode in case performance stats aren't
supported in a given nvdimm.

Also the initialization of 'papr_scm_priv.stat_buffer_len' is moved
from papr_scm_nvdimm_init() to papr_scm_probe() so that it value is
available when 'papr_nd_attribute_visible()' is called during nvdimm
initialization.

Fixes: 2d02bf835e57('powerpc/papr_scm: Fetch nvdimm performance stats from PHYP')
Signed-off-by: Vaibhav Jain <redacted>
---
 arch/powerpc/platforms/pseries/papr_scm.c | 37 ++++++++++++++++-------
 1 file changed, 26 insertions(+), 11 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
index 12f1513f0fca..90f0af8fefe8 100644
--- a/arch/powerpc/platforms/pseries/papr_scm.c
+++ b/arch/powerpc/platforms/pseries/papr_scm.c

@@ -907,6 +907,20 @@ static ssize_t flags_show(struct device *dev,
 }
 DEVICE_ATTR_RO(flags);
 
+umode_t papr_nd_attribute_visible(struct kobject *kobj, struct attribute *attr,
+				  int n)
+{
+	struct device *dev = container_of(kobj, typeof(*dev), kobj);
+	struct nvdimm *nvdimm = to_nvdimm(dev);
+	struct papr_scm_priv *p = nvdimm_provider_data(nvdimm);
+
+	/* For if perf-stats not available remove perf_stats sysfs */
+	if (attr == &dev_attr_perf_stats.attr && p->stat_buffer_len == 0)
+		return 0;
+
+	return attr->mode;
+}
+
 /* papr_scm specific dimm attributes */
 static struct attribute *papr_nd_attributes[] = {
 	&dev_attr_flags.attr,

@@ -916,6 +930,7 @@ static struct attribute *papr_nd_attributes[] = {
 
 static struct attribute_group papr_nd_attribute_group = {
 	.name = "papr",
+	.is_visible = papr_nd_attribute_visible,
 	.attrs = papr_nd_attributes,
 };
 

@@ -931,7 +946,6 @@ static int papr_scm_nvdimm_init(struct papr_scm_priv *p)
 	struct nd_region_desc ndr_desc;
 	unsigned long dimm_flags;
 	int target_nid, online_nid;
-	ssize_t stat_size;
 
 	p->bus_desc.ndctl = papr_scm_ndctl;
 	p->bus_desc.module = THIS_MODULE;

@@ -1016,16 +1030,6 @@ static int papr_scm_nvdimm_init(struct papr_scm_priv *p)
 	list_add_tail(&p->region_list, &papr_nd_regions);
 	mutex_unlock(&papr_ndr_lock);
 
-	/* Try retriving the stat buffer and see if its supported */
-	stat_size = drc_pmem_query_stats(p, NULL, 0);
-	if (stat_size > 0) {
-		p->stat_buffer_len = stat_size;
-		dev_dbg(&p->pdev->dev, "Max perf-stat size %lu-bytes\n",
-			p->stat_buffer_len);
-	} else {
-		dev_info(&p->pdev->dev, "Dimm performance stats unavailable\n");
-	}
-
 	return 0;
 
 err:	nvdimm_bus_unregister(p->bus);

@@ -1102,6 +1106,7 @@ static int papr_scm_probe(struct platform_device *pdev)
 	u64 blocks, block_size;
 	struct papr_scm_priv *p;
 	const char *uuid_str;
+	ssize_t stat_size;
 	u64 uuid[2];
 	int rc;
 

@@ -1179,6 +1184,16 @@ static int papr_scm_probe(struct platform_device *pdev)
 	p->res.name  = pdev->name;
 	p->res.flags = IORESOURCE_MEM;
 
+	/* Try retriving the stat buffer and see if its supported */
+	stat_size = drc_pmem_query_stats(p, NULL, 0);
+	if (stat_size > 0) {
+		p->stat_buffer_len = stat_size;
+		dev_dbg(&p->pdev->dev, "Max perf-stat size %lu-bytes\n",
+			p->stat_buffer_len);
+	} else {
+		dev_info(&p->pdev->dev, "Dimm performance stats unavailable\n");
+	}

With this patch https://lore.kernel.org/linuxppc-dev/20210505191606.51666-1-vaibhav@linux.ibm.com
We are adding details of whyy performance stat query hcall failed. Do we
need to print again here?  Are we being more verbose here?

Yes agree this looks more verbose with the other patch you mentioned. I
have sent out a v2 of this patch with this dev_info removed.

-aneesh
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-- 
Cheers
~ Vaibhav