Re: [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 <vaibhav(a)linux.ibm.com&gt; --- 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"); + }