[RFC PATCH 1/4] libnvdimm/namespace: Make namespace size validation arch dependent

[Aneesh Kumar K.V]

The page size used to map the namespace is arch dependent. For example
architectures like ppc64 use 16MB page size for direct-mapping. If the namespace
size is not aligned to the mapping page size, we can observe kernel crash
during namespace init and destroy.

This is due to kernel doing partial map/unmap of the resource range

BUG: Unable to handle kernel data access at 0xc001000406000000
Faulting instruction address: 0xc000000000090790
NIP [c000000000090790] arch_add_memory+0xc0/0x130
LR [c000000000090744] arch_add_memory+0x74/0x130
Call Trace:
 arch_add_memory+0x74/0x130 (unreliable)
 memremap_pages+0x74c/0xa30
 devm_memremap_pages+0x3c/0xa0
 pmem_attach_disk+0x188/0x770
 nvdimm_bus_probe+0xd8/0x470
 really_probe+0x148/0x570
 driver_probe_device+0x19c/0x1d0
 device_driver_attach+0xcc/0x100
 bind_store+0x134/0x1c0
 drv_attr_store+0x44/0x60
 sysfs_kf_write+0x74/0xc0
 kernfs_fop_write+0x1b4/0x290
 __vfs_write+0x3c/0x70
 vfs_write+0xd0/0x260
 ksys_write+0xdc/0x130
 system_call+0x5c/0x68

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar at linux.ibm.com>
---
 arch/arm64/mm/flush.c     | 11 +++++++++++
 arch/powerpc/lib/pmem.c   | 21 +++++++++++++++++++--
 arch/x86/mm/pageattr.c    | 12 ++++++++++++
 include/linux/libnvdimm.h |  1 +
 4 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/mm/flush.c b/arch/arm64/mm/flush.c
index ac485163a4a7..90c54c600023 100644
--- a/arch/arm64/mm/flush.c
+++ b/arch/arm64/mm/flush.c
@@ -91,4 +91,15 @@ void arch_invalidate_pmem(void *addr, size_t size)
 	__inval_dcache_area(addr, size);
 }
 EXPORT_SYMBOL_GPL(arch_invalidate_pmem);
+
+unsigned long arch_validate_namespace_size(unsigned int ndr_mappings, unsigned long size)
+{
+	u32 remainder;
+
+	div_u64_rem(size, PAGE_SIZE * ndr_mappings, &remainder);
+	if (remainder)
+		return PAGE_SIZE * ndr_mappings;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(arch_validate_namespace_size);
 #endif
diff --git a/arch/powerpc/lib/pmem.c b/arch/powerpc/lib/pmem.c
index 377712e85605..2e661a08dae5 100644
--- a/arch/powerpc/lib/pmem.c
+++ b/arch/powerpc/lib/pmem.c
@@ -17,14 +17,31 @@ void arch_wb_cache_pmem(void *addr, size_t size)
 	unsigned long start = (unsigned long) addr;
 	flush_dcache_range(start, start + size);
 }
-EXPORT_SYMBOL(arch_wb_cache_pmem);
+EXPORT_SYMBOL_GPL(arch_wb_cache_pmem);
 
 void arch_invalidate_pmem(void *addr, size_t size)
 {
 	unsigned long start = (unsigned long) addr;
 	flush_dcache_range(start, start + size);
 }
-EXPORT_SYMBOL(arch_invalidate_pmem);
+EXPORT_SYMBOL_GPL(arch_invalidate_pmem);
+
+unsigned long arch_validate_namespace_size(unsigned int ndr_mappings, unsigned long size)
+{
+	u32 remainder;
+	unsigned long linear_map_size;
+
+	if (radix_enabled())
+		linear_map_size = PAGE_SIZE;
+	else
+		linear_map_size = (1UL << mmu_psize_defs[mmu_linear_psize].shift);
+
+	div_u64_rem(size, linear_map_size * ndr_mappings, &remainder);
+	if (remainder)
+		return linear_map_size * ndr_mappings;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(arch_validate_namespace_size);
 
 /*
  * CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE symbols
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 0d09cc5aad61..023329d7dfac 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -310,6 +310,18 @@ void arch_invalidate_pmem(void *addr, size_t size)
 }
 EXPORT_SYMBOL_GPL(arch_invalidate_pmem);
 
+unsigned long arch_validate_namespace_size(unsigned int ndr_mappings, unsigned long size)
+{
+	u32 remainder;
+
+	div_u64_rem(size, PAGE_SIZE * ndr_mappings, &remainder);
+	if (remainder)
+		return PAGE_SIZE * ndr_mappings;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(arch_validate_namespace_size);
+
+
 static void __cpa_flush_all(void *arg)
 {
 	unsigned long cache = (unsigned long)arg;
diff --git a/include/linux/libnvdimm.h b/include/linux/libnvdimm.h
index b6eddf912568..e2f8387d9ef4 100644
--- a/include/linux/libnvdimm.h
+++ b/include/linux/libnvdimm.h
@@ -291,4 +291,5 @@ static inline void arch_invalidate_pmem(void *addr, size_t size)
 }
 #endif
 
+unsigned long arch_validate_namespace_size(unsigned int ndr_mappings, unsigned long size);
 #endif /* __LIBNVDIMM_H__ */
-- 
2.21.0