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Subject[PATCH 4.9 36/39] libnvdimm, dax: fix 1GB-aligned namespaces vs physical misalignment
Date
4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dan Williams <dan.j.williams@intel.com>

commit 41fce90f26333c4fa82e8e43b9ace86c4e8a0120 upstream.

The following namespace configuration attempt:

# ndctl create-namespace -e namespace0.0 -m devdax -a 1G -f
libndctl: ndctl_dax_enable: dax0.1: failed to enable
Error: namespace0.0: failed to enable

failed to reconfigure namespace: No such device or address

...fails when the backing memory range is not physically aligned to 1G:

# cat /proc/iomem | grep Persistent
210000000-30fffffff : Persistent Memory (legacy)

In the above example the 4G persistent memory range starts and ends on a
256MB boundary.

We handle this case correctly when needing to handle cases that violate
section alignment (128MB) collisions against "System RAM", and we simply
need to extend that padding/truncation for the 1GB alignment use case.

Cc: <stable@vger.kernel.org>
Fixes: 315c562536c4 ("libnvdimm, pfn: add 'align' attribute...")
Reported-and-tested-by: Jane Chu <jane.chu@oracle.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/nvdimm/pfn_devs.c | 15 ++++++++++++---
include/linux/kernel.h | 1 +
2 files changed, 13 insertions(+), 3 deletions(-)

--- a/drivers/nvdimm/pfn_devs.c
+++ b/drivers/nvdimm/pfn_devs.c
@@ -563,6 +563,12 @@ static struct vmem_altmap *__nvdimm_setu
return altmap;
}

+static u64 phys_pmem_align_down(struct nd_pfn *nd_pfn, u64 phys)
+{
+ return min_t(u64, PHYS_SECTION_ALIGN_DOWN(phys),
+ ALIGN_DOWN(phys, nd_pfn->align));
+}
+
static int nd_pfn_init(struct nd_pfn *nd_pfn)
{
u32 dax_label_reserve = is_nd_dax(&nd_pfn->dev) ? SZ_128K : 0;
@@ -618,13 +624,16 @@ static int nd_pfn_init(struct nd_pfn *nd
start = nsio->res.start;
size = PHYS_SECTION_ALIGN_UP(start + size) - start;
if (region_intersects(start, size, IORESOURCE_SYSTEM_RAM,
- IORES_DESC_NONE) == REGION_MIXED) {
+ IORES_DESC_NONE) == REGION_MIXED
+ || !IS_ALIGNED(start + resource_size(&nsio->res),
+ nd_pfn->align)) {
size = resource_size(&nsio->res);
- end_trunc = start + size - PHYS_SECTION_ALIGN_DOWN(start + size);
+ end_trunc = start + size - phys_pmem_align_down(nd_pfn,
+ start + size);
}

if (start_pad + end_trunc)
- dev_info(&nd_pfn->dev, "%s section collision, truncate %d bytes\n",
+ dev_info(&nd_pfn->dev, "%s alignment collision, truncate %d bytes\n",
dev_name(&ndns->dev), start_pad + end_trunc);

/*
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -46,6 +46,7 @@
#define REPEAT_BYTE(x) ((~0ul / 0xff) * (x))

#define ALIGN(x, a) __ALIGN_KERNEL((x), (a))
+#define ALIGN_DOWN(x, a) __ALIGN_KERNEL((x) - ((a) - 1), (a))
#define __ALIGN_MASK(x, mask) __ALIGN_KERNEL_MASK((x), (mask))
#define PTR_ALIGN(p, a) ((typeof(p))ALIGN((unsigned long)(p), (a)))
#define IS_ALIGNED(x, a) (((x) & ((typeof(x))(a) - 1)) == 0)

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