Re: [PATCH v2] powerpc/papr_scm: Fix warning triggered by perf_stats_show()
On Sat, 12 Sep 2020 13:44:51 +0530, Vaibhav Jain wrote: > 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@4411: > 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 > > [...] Applied to powerpc/next. [1/1] powerpc/papr_scm: Fix warning triggered by perf_stats_show() https://git.kernel.org/powerpc/c/ca78ef2f08ccfa29b711d644964cdf9d7ace15e5 cheers
Re: [PATCH v2] powerpc/papr_scm: Fix warning triggered by perf_stats_show()
Michael Ellerman writes:
> Vaibhav Jain writes:
>> 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@4411:
>>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')
>
> Please don't word wrap the Fixes tag it breaks b4.
>
> I've fixed it up this time.
Thanks Mpe
>
> cheers
--
Cheers
~ Vaibhav
Re: [PATCH v2] powerpc/papr_scm: Fix warning triggered by perf_stats_show()
Vaibhav Jain writes:
> 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@4411:
> 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')
Please don't word wrap the Fixes tag it breaks b4.
I've fixed it up this time.
cheers
Re: [PATCH v2] powerpc/papr_scm: Fix warning triggered by perf_stats_show()
On Sat, Sep 12, 2020 at 01:44:51PM +0530, Vaibhav Jain wrote:
> 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@4411:
> 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
Reviewed-by: Ira Weiny
> ---
> Changelog:
>
> v2: Added an explicit cast to the expression calling 'seq_buf_used()'
> and triggering this issue. [ Ira ]
> ---
> arch/powerpc/platforms/pseries/papr_scm.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> 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);
>
> --
> 2.26.2
>
[PATCH v2] powerpc/papr_scm: Fix warning triggered by perf_stats_show()
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@4411:
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
---
Changelog:
v2: Added an explicit cast to the expression calling 'seq_buf_used()'
and triggering this issue. [ Ira ]
---
arch/powerpc/platforms/pseries/papr_scm.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
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);
--
2.26.2
