From: Vaibhav Jain <vaibhav@linux.ibm.com> To: linuxppc-dev@lists.ozlabs.org, linux-nvdimm@lists.01.org Cc: Vaibhav Jain <vaibhav@linux.ibm.com>, "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>, Michael Ellerman <mpe@ellerman.id.au> Subject: [PATCH v2] powerpc/papr_scm: Fix warning triggered by perf_stats_show() Date: Sat, 12 Sep 2020 13:44:51 +0530 [thread overview] Message-ID: <20200912081451.66225-1-vaibhav@linux.ibm.com> (raw) 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(-) 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
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From: Vaibhav Jain <vaibhav@linux.ibm.com> To: linuxppc-dev@lists.ozlabs.org, linux-nvdimm@lists.01.org Cc: Santosh Sivaraj <santosh@fossix.org>, Oliver O'Halloran <oohall@gmail.com>, "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>, Vaibhav Jain <vaibhav@linux.ibm.com>, Dan Williams <dan.j.williams@intel.com>, Ira Weiny <ira.weiny@intel.com> Subject: [PATCH v2] powerpc/papr_scm: Fix warning triggered by perf_stats_show() Date: Sat, 12 Sep 2020 13:44:51 +0530 [thread overview] Message-ID: <20200912081451.66225-1-vaibhav@linux.ibm.com> (raw) 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(-) 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 reply other threads:[~2020-09-12 8:15 UTC|newest] Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-09-12 8:14 Vaibhav Jain [this message] 2020-09-12 8:14 ` [PATCH v2] powerpc/papr_scm: Fix warning triggered by perf_stats_show() Vaibhav Jain 2020-09-14 16:56 ` Ira Weiny 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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