From: Ira Weiny <ira.weiny@intel.com> To: Vaibhav Jain <vaibhav@linux.ibm.com> Cc: linuxppc-dev@lists.ozlabs.org, linux-nvdimm@lists.01.org, "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>, Michael Ellerman <mpe@ellerman.id.au> Subject: Re: [PATCH v2] powerpc/papr_scm: Fix warning triggered by perf_stats_show() Date: Mon, 14 Sep 2020 09:56:51 -0700 [thread overview] Message-ID: <20200914165651.GR1930795@iweiny-DESK2.sc.intel.com> (raw) In-Reply-To: <20200912081451.66225-1-vaibhav@linux.ibm.com> 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 > _______________________________________________ Linux-nvdimm mailing list -- linux-nvdimm@lists.01.org To unsubscribe send an email to linux-nvdimm-leave@lists.01.org
WARNING: multiple messages have this Message-ID (diff)
From: Ira Weiny <ira.weiny@intel.com> To: Vaibhav Jain <vaibhav@linux.ibm.com> Cc: Santosh Sivaraj <santosh@fossix.org>, linux-nvdimm@lists.01.org, "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>, Oliver O'Halloran <oohall@gmail.com>, Dan Williams <dan.j.williams@intel.com>, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH v2] powerpc/papr_scm: Fix warning triggered by perf_stats_show() Date: Mon, 14 Sep 2020 09:56:51 -0700 [thread overview] Message-ID: <20200914165651.GR1930795@iweiny-DESK2.sc.intel.com> (raw) In-Reply-To: <20200912081451.66225-1-vaibhav@linux.ibm.com> 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 >
next prev parent reply other threads:[~2020-09-14 16:56 UTC|newest] Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-09-12 8:14 [PATCH v2] powerpc/papr_scm: Fix warning triggered by perf_stats_show() Vaibhav Jain 2020-09-12 8:14 ` Vaibhav Jain 2020-09-14 16:56 ` Ira Weiny [this message] 2020-09-14 16:56 ` Ira Weiny 2020-09-15 11:30 ` Michael Ellerman 2020-09-15 11:30 ` Michael Ellerman 2020-09-15 16:03 ` Vaibhav Jain 2020-09-15 16:03 ` Vaibhav Jain 2020-09-17 11:27 ` Michael Ellerman 2020-09-17 11:27 ` Michael Ellerman
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