A warning is reported by the kernel in case perf_stats_show() returns
an error code. The warning is of the form below:
papr_scm ibm,persistent-memory:ibm,pmemory@44100001:
Failed to query performance stats, Err:-10
dev_attr_show: perf_stats_show+0x0/0x1c0 [papr_scm] returned bad count
fill_read_buffer: dev_attr_show+0x0/0xb0 returned bad count
On investigation it looks like that the compiler is silently truncating the
return value of drc_pmem_query_stats() from 'long' to 'int', since the
variable used to store the return code 'rc' is an 'int'. This
truncated value is then returned back as a 'ssize_t' back from
perf_stats_show() to 'dev_attr_show()' which thinks of it as a large
unsigned number and triggers this warning..
To fix this we update the type of variable 'rc' from 'int' to
'ssize_t' that prevents the compiler from truncating the return value
of drc_pmem_query_stats() and returning correct signed value back from
perf_stats_show().
Fixes: 2d02bf835e573 ('powerpc/papr_scm: Fetch nvdimm performance
stats from PHYP')
Signed-off-by: Vaibhav Jain <vaib...@linux.ibm.com>
---
arch/powerpc/platforms/pseries/papr_scm.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/platforms/pseries/papr_scm.c
b/arch/powerpc/platforms/pseries/papr_scm.c
index a88a707a608aa..9f00b61676ab9 100644
--- a/arch/powerpc/platforms/pseries/papr_scm.c
+++ b/arch/powerpc/platforms/pseries/papr_scm.c
@@ -785,7 +785,8 @@ static int papr_scm_ndctl(struct nvdimm_bus_descriptor
*nd_desc,
static ssize_t perf_stats_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
- int index, rc;
+ int index;
+ ssize_t rc;
struct seq_buf s;
struct papr_scm_perf_stat *stat;
struct papr_scm_perf_stats *stats;
--
2.26.2
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