| Message ID | 146068804768.24085.7722589204633361307.stgit@dwillia2-desk3.jf.intel.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 0a370d261c80 |
| Headers | show |
On Donnerstag, 14. April 2016 19:40:47 CEST Dan Williams wrote: > The ACPI specification does not specify the state of data after a clear > poison operation. Potential future libnvdimm bus implementations for > other architectures also might not specify or disagree on the state of > data after clear poison. Clarify why we write twice. > > Reported-by: Jeff Moyer <jmoyer@redhat.com> > Reported-by: Vishal Verma <vishal.l.verma@intel.com> > Signed-off-by: Dan Williams <dan.j.williams@intel.com> > --- Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Dan Williams <dan.j.williams@intel.com> writes: > The ACPI specification does not specify the state of data after a clear > poison operation. Potential future libnvdimm bus implementations for > other architectures also might not specify or disagree on the state of > data after clear poison. Clarify why we write twice. Thanks, Dan, looks good. Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
On Thu, 2016-04-14 at 19:40 -0700, Dan Williams wrote: > The ACPI specification does not specify the state of data after a > clear > poison operation. Potential future libnvdimm bus implementations for > other architectures also might not specify or disagree on the state > of > data after clear poison. Clarify why we write twice. > > Reported-by: Jeff Moyer <jmoyer@redhat.com> > Reported-by: Vishal Verma <vishal.l.verma@intel.com> > Signed-off-by: Dan Williams <dan.j.williams@intel.com> > --- > drivers/nvdimm/pmem.c | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) Looks good, thanks! Reviewed-by: Vishal Verma <vishal.l.verma@intel.com> > > diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c > index c6befaa9c708..d9a0dbc2d023 100644 > --- a/drivers/nvdimm/pmem.c > +++ b/drivers/nvdimm/pmem.c > @@ -86,6 +86,20 @@ static int pmem_do_bvec(struct pmem_device *pmem, > struct page *page, > flush_dcache_page(page); > } > } else { > + /* > + * Note that we write the data both before and after > + * clearing poison. The write before clear poison > + * handles situations where the latest written data > is > + * preserved and the clear poison operation simply > marks > + * the address range as valid without changing the > data. > + * In this case application software can assume that > an > + * interrupted write will either return the new good > + * data or an error. > + * > + * However, if pmem_clear_poison() leaves the data > in an > + * indeterminate state we need to perform the write > + * after clear poison. > + */ > flush_dcache_page(page); > memcpy_to_pmem(pmem_addr, mem + off, len); > if (unlikely(bad_pmem)) { >
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c index c6befaa9c708..d9a0dbc2d023 100644 --- a/drivers/nvdimm/pmem.c +++ b/drivers/nvdimm/pmem.c @@ -86,6 +86,20 @@ static int pmem_do_bvec(struct pmem_device *pmem, struct page *page, flush_dcache_page(page); } } else { + /* + * Note that we write the data both before and after + * clearing poison. The write before clear poison + * handles situations where the latest written data is + * preserved and the clear poison operation simply marks + * the address range as valid without changing the data. + * In this case application software can assume that an + * interrupted write will either return the new good + * data or an error. + * + * However, if pmem_clear_poison() leaves the data in an + * indeterminate state we need to perform the write + * after clear poison. + */ flush_dcache_page(page); memcpy_to_pmem(pmem_addr, mem + off, len); if (unlikely(bad_pmem)) {
The ACPI specification does not specify the state of data after a clear poison operation. Potential future libnvdimm bus implementations for other architectures also might not specify or disagree on the state of data after clear poison. Clarify why we write twice. Reported-by: Jeff Moyer <jmoyer@redhat.com> Reported-by: Vishal Verma <vishal.l.verma@intel.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com> --- drivers/nvdimm/pmem.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+)