| Message ID | 20200912081451.66225-1-vaibhav@linux.ibm.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | ca78ef2f08ccfa29b711d644964cdf9d7ace15e5 |
| Headers | show |
| Series | [v2] powerpc/papr_scm: Fix warning triggered by perf_stats_show() | expand |
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@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 <vaibhav@linux.ibm.com> Reviewed-by: Ira Weiny <ira.weiny@intel.com> > --- > 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 >
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. cheers
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
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@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 > > [...] Applied to powerpc/next. [1/1] powerpc/papr_scm: Fix warning triggered by perf_stats_show() https://git.kernel.org/powerpc/c/ca78ef2f08ccfa29b711d644964cdf9d7ace15e5 cheers
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);
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 <vaibhav@linux.ibm.com> --- 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(-)