On Fri, Jun 5, 2020 at 10:13 AM Ira Weiny <ira.we...@intel.com> wrote: > > On Fri, Jun 05, 2020 at 05:11:34AM +0530, Vaibhav Jain wrote: > > Since papr_scm_ndctl() can be called from outside papr_scm, its > > exposed to the possibility of receiving NULL as value of 'cmd_rc' > > argument. This patch updates papr_scm_ndctl() to protect against such > > possibility by assigning it pointer to a local variable in case cmd_rc > > == NULL. > > > > Finally the patch also updates the 'default' clause of the switch-case > > block removing a 'return' statement thereby ensuring that value of > > 'cmd_rc' is always logged when papr_scm_ndctl() returns. > > > > Cc: "Aneesh Kumar K . V" <aneesh.ku...@linux.ibm.com> > > Cc: Dan Williams <dan.j.willi...@intel.com> > > Cc: Michael Ellerman <m...@ellerman.id.au> > > Cc: Ira Weiny <ira.we...@intel.com> > > Signed-off-by: Vaibhav Jain <vaib...@linux.ibm.com> > > --- > > Changelog: > > > > v9..v10 > > * New patch in the series > > Thanks for making this a separate patch it is easier to see what is going on > here. > > > --- > > arch/powerpc/platforms/pseries/papr_scm.c | 10 ++++++++-- > > 1 file changed, 8 insertions(+), 2 deletions(-) > > > > diff --git a/arch/powerpc/platforms/pseries/papr_scm.c > > b/arch/powerpc/platforms/pseries/papr_scm.c > > index 0c091622b15e..6512fe6a2874 100644 > > --- a/arch/powerpc/platforms/pseries/papr_scm.c > > +++ b/arch/powerpc/platforms/pseries/papr_scm.c > > @@ -355,11 +355,16 @@ static int papr_scm_ndctl(struct > > nvdimm_bus_descriptor *nd_desc, > > { > > struct nd_cmd_get_config_size *get_size_hdr; > > struct papr_scm_priv *p; > > + int rc; > > > > /* Only dimm-specific calls are supported atm */ > > if (!nvdimm) > > return -EINVAL; > > > > + /* Use a local variable in case cmd_rc pointer is NULL */ > > + if (!cmd_rc) > > + cmd_rc = &rc; > > + > > This protects you from the NULL. However... > > > p = nvdimm_provider_data(nvdimm); > > > > switch (cmd) { > > @@ -381,12 +386,13 @@ static int papr_scm_ndctl(struct > > nvdimm_bus_descriptor *nd_desc, > > break; > > > > default: > > - return -EINVAL; > > + dev_dbg(&p->pdev->dev, "Unknown command = %d\n", cmd); > > + *cmd_rc = -EINVAL; > > ... I think you are conflating rc and cmd_rc... > > > } > > > > dev_dbg(&p->pdev->dev, "returned with cmd_rc = %d\n", *cmd_rc); > > > > - return 0; > > + return *cmd_rc; > > ... this changes the behavior of the current commands. Now if the underlying > papr_scm_meta_[get|set]() fails you return that failure as rc rather than 0. > > Is that ok?
The expectation is that rc is "did the command get sent to the device, or did it fail for 'transport' reasons". The role of cmd_rc is to translate the specific status response of the command into a common error code. The expectations are: rc < 0: Error code, Linux terminated the ioctl before talking to hardware rc == 0: Linux successfully submitted the command to hardware, cmd_rc is valid for command specific response rc > 0: Linux successfully submitted the command, but detected that only a subset of the data was accepted for "write"-style commands, or that only subset of data was returned for "read"-style commands. I.e. short-write / short-read semantics. cmd_rc is valid in this case and its up to userspace to determine if a short transfer is an error or not. > Also 'logging cmd_rc' in the invalid cmd case does not seem quite right unless > you really want rc to be cmd_rc. > > The architecture is designed to separate errors which occur in the kernel vs > errors in the firmware/dimm. Are they always the same? The current code > differentiates them. Yeah, they're distinct, transport vs end-point / command-specific status returns.