From: Vaibhav Jain vaibhav@linux.ibm.com
[ 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@linux.ibm.com Reviewed-by: Dan Williams dan.j.williams@intel.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/20210513092349.285021-1-vaibhav@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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 92e2db0e2d3d..95254cec92bf 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@lists.ozlabs.org, nvdimm@lists.linux.dev, 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 8335e13836db..d34e6eb4be0d 100644 --- a/arch/powerpc/platforms/pseries/papr_scm.c +++ b/arch/powerpc/platforms/pseries/papr_scm.c @@ -901,6 +901,20 @@ 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, @@ -910,6 +924,7 @@ 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, };
@@ -925,7 +940,6 @@ 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; @@ -1010,16 +1024,6 @@ 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); @@ -1097,6 +1101,7 @@ 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;
@@ -1181,6 +1186,14 @@ 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;