Re: [PATCH v2] powerpc/papr_scm: Fix warning triggered by perf_stats_show()

[Vaibhav Jain <vaibhav@linux.ibm.com>]

Michael Ellerman <mpe@ellerman.id.au> writes:

> Vaibhav Jain <vaibhav@linux.ibm.com> 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@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')
>
> Please don't word wrap the Fixes tag it breaks b4.
>
> I've fixed it up this time.

Thanks Mpe

>
> cheers

-- 
Cheers
~ Vaibhav