From: Vaibhav Jain <vaibhav@xxxxxxxxxxxxx>
[ Upstream commit ed78f56e1271f108e8af61baeba383dcd77adbec ]
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.
Even though 'perf_stats' attribute is available since v5.9, there are
no known user-space tools/scripts that are dependent on presence of its
sysfs file. Hence I dont expect any user-space breakage with this
patch.
Fixes: 2d02bf835e57 ("powerpc/papr_scm: Fetch nvdimm performance stats from PHYP")
Signed-off-by: Vaibhav Jain <vaibhav@xxxxxxxxxxxxx>
Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20210513092349.285021-1-vaibhav@xxxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
Documentation/ABI/testing/sysfs-bus-papr-pmem | 8 +++--
arch/powerpc/platforms/pseries/papr_scm.c | 35 +++++++++++++------
2 files changed, 29 insertions(+), 14 deletions(-)
diff --git a/Documentation/ABI/testing/sysfs-bus-papr-pmem b/Documentation/ABI/testing/sysfs-bus-papr-pmem
index 8316c33862a0..0aa02bf2bde5 100644
--- a/Documentation/ABI/testing/sysfs-bus-papr-pmem
+++ b/Documentation/ABI/testing/sysfs-bus-papr-pmem
@@ -39,9 +39,11 @@ KernelVersion: v5.9
Contact: linuxppc-dev <linuxppc-dev@xxxxxxxxxxxxxxxx>, linux-nvdimm@xxxxxxxxxxxx,
Description:
(RO) Report various performance stats related to papr-scm NVDIMM
- device. Each stat is reported on a new line with each line
- composed of a stat-identifier followed by it value. Below are
- currently known dimm performance stats which are reported:
+ device. This attribute is only available for NVDIMM devices
+ that support reporting NVDIMM performance stats. Each stat is
+ reported on a new line with each line composed of a
+ stat-identifier followed by it value. Below are currently known
+ dimm performance stats which are reported:
* "CtlResCt" : Controller Reset Count
* "CtlResTm" : Controller Reset Elapsed Time
diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
index 0693bc8d70ac..057acbb9116d 100644
--- a/arch/powerpc/platforms/pseries/papr_scm.c
+++ b/arch/powerpc/platforms/pseries/papr_scm.c
@@ -868,6 +868,20 @@ static ssize_t flags_show(struct device *dev,
}
DEVICE_ATTR_RO(flags);
+static umode_t papr_nd_attribute_visible(struct kobject *kobj,
+ struct attribute *attr, int n)
+{
+ struct device *dev = kobj_to_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,
@@ -877,6 +891,7 @@ 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,
};
@@ -892,7 +907,6 @@ 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;
@@ -963,16 +977,6 @@ 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);
@@ -1050,6 +1054,7 @@ static int papr_scm_probe(struct platform_device *pdev)
struct papr_scm_priv *p;
u8 uuid_raw[UUID_SIZE];
const char *uuid_str;
+ ssize_t stat_size;
uuid_t uuid;
int rc;
@@ -1133,6 +1138,14 @@ static int papr_scm_probe(struct platform_device *pdev)
p->res.name = pdev->name;
p->res.flags = IORESOURCE_MEM;
+ /* Try retrieving 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);
+ }
+
rc = papr_scm_nvdimm_init(p);
if (rc)
goto err2;
--
2.30.2
