Vaibhav Jain <vaibhav@xxxxxxxxxxxxx> writes: > In case a platform doesn't provide explicit flush-hints but provides an > explicit flush callback via ND_REGION_ASYNC region flag, then > nvdimm_has_flush() still returns '0' indicating that writes do not > require flushing. This happens on PPC64 with patch at [1] applied, > where 'deep_flush' of a region was denied even though an explicit > flush function was provided. > > Similar problem is also seen with virtio-pmem where the 'deep_flush' > sysfs attribute is not visible as in absence of any registered nvdimm, > 'nd_region->ndr_mappings == 0'. > > Fix this by updating nvdimm_has_flush() adding a condition to > nvdimm_has_flush() testing for ND_REGION_ASYNC flag on the region > and see if a 'region->flush' callback is assigned. Also remove > explicit test for 'nd_region->ndr_mapping' since regions can be marked > 'ND_REGION_SYNC' without any explicit mappings as in case of > virtio-pmem. Do we need to check for ND_REGION_ASYNC? What if the backend wants to provide a synchronous dax region but with different deep flush semantic than writing to wpq flush address? ie, > > References: > [1] "powerpc/papr_scm: Implement support for H_SCM_FLUSH hcall" > https://lore.kernel.org/linux-nvdimm/161703936121.36.7260632399 582101498.stgit@e1fbed493c87 > > Cc: <stable@xxxxxxxxxxxxxxx> > Fixes: c5d4355d10d4 ("libnvdimm: nd_region flush callback support") > Reported-by: Shivaprasad G Bhat <sbhat@xxxxxxxxxxxxx> > Signed-off-by: Vaibhav Jain <vaibhav@xxxxxxxxxxxxx> > --- > Changelog: > > v2: > * Added the fixes tag and addressed the patch to stable tree [ Aneesh ] > * Updated patch description to address the virtio-pmem case. > * Removed test for 'nd_region->ndr_mappings' from beginning of > nvdimm_has_flush() to handle the virtio-pmem case. > --- > drivers/nvdimm/region_devs.c | 14 +++++++++----- > 1 file changed, 9 insertions(+), 5 deletions(-) > > diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c > index ef23119db574..cdf5eb6fa425 100644 > --- a/drivers/nvdimm/region_devs.c > +++ b/drivers/nvdimm/region_devs.c > @@ -1234,11 +1234,15 @@ int nvdimm_has_flush(struct nd_region *nd_region) > { > int i; > > - /* no nvdimm or pmem api == flushing capability unknown */ > - if (nd_region->ndr_mappings == 0 > - || !IS_ENABLED(CONFIG_ARCH_HAS_PMEM_API)) > + /* no pmem api == flushing capability unknown */ > + if (!IS_ENABLED(CONFIG_ARCH_HAS_PMEM_API)) > return -ENXIO; > > + /* Test if an explicit flush function is defined */ > + if (test_bit(ND_REGION_ASYNC, &nd_region->flags) && nd_region->flush) > + return 1; > + if (nd_region->flush) return 1 > + /* Test if any flush hints for the region are available */ > for (i = 0; i < nd_region->ndr_mappings; i++) { > struct nd_mapping *nd_mapping = &nd_region->mapping[i]; > struct nvdimm *nvdimm = nd_mapping->nvdimm; > @@ -1249,8 +1253,8 @@ int nvdimm_has_flush(struct nd_region *nd_region) > } > > /* > - * The platform defines dimm devices without hints, assume > - * platform persistence mechanism like ADR > + * The platform defines dimm devices without hints nor explicit flush, > + * assume platform persistence mechanism like ADR > */ > return 0; > } > -- > 2.30.2 > _______________________________________________ > Linux-nvdimm mailing list -- linux-nvdimm@xxxxxxxxxxxx > To unsubscribe send an email to linux-nvdimm-leave@xxxxxxxxxxxx
