This is a note to let you know that I've just added the patch titled
powerpc/papr_scm: Fix warning triggered by perf_stats_show()
to the 5.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
powerpc-papr_scm-fix-warning-triggered-by-perf_stats.patch
and it can be found in the queue-5.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 217b5b8951d743737d3468cbb15dc15be7d3ecf5
Author: Vaibhav Jain <vaibhav@xxxxxxxxxxxxx>
Date: Sat Sep 12 13:44:51 2020 +0530
powerpc/papr_scm: Fix warning triggered by perf_stats_show()
[ Upstream commit ca78ef2f08ccfa29b711d644964cdf9d7ace15e5 ]
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: 2d02bf835e57 ("powerpc/papr_scm: Fetch nvdimm performance stats from PHYP")
Signed-off-by: Vaibhav Jain <vaibhav@xxxxxxxxxxxxx>
Reviewed-by: Ira Weiny <ira.weiny@xxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20200912081451.66225-1-vaibhav@xxxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
index a88a707a608aa..5493bc847bd08 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;
@@ -820,7 +821,7 @@ static ssize_t perf_stats_show(struct device *dev,
free_stats:
kfree(stats);
- return rc ? rc : seq_buf_used(&s);
+ return rc ? rc : (ssize_t)seq_buf_used(&s);
}
DEVICE_ATTR_ADMIN_RO(perf_stats);
