In case a platform doesn't provide explicit flush-hints but provides an explicit flush callback, 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() to test if a 'region->flush' callback is assigned. Also remove explicit test for 'nd_region->ndr_mapping' since regions may need 'flush' without any explicit mappings as in case of virtio-pmem. References: [1] "powerpc/papr_scm: Implement support for H_SCM_FLUSH hcall" https://lore.kernel.org/linux-nvdimm/161703936121.36.7260632399582101498.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: v3: * Removed the test for ND_REGION_SYNC to handle case where a synchronous region still wants to expose a deep-flush function. [ Aneesh ] * Updated patch title and description from previous patch https://lore.kernel.org/linux-nvdimm/5e64778d-bf48-9f10-7d3d-5e530e5db590@xxxxxxxxxxxxx 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..c4b17bdd527f 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 (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
