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Subject[PATCH v9 12/12] libnvdimm/pfn: Stop padding pmem namespaces to section alignment
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Now that the mm core supports section-unaligned hotplug of ZONE_DEVICE
memory, we no longer need to add padding at pfn/dax device creation
time. The kernel will still honor padding established by older kernels.

Reported-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
drivers/nvdimm/pfn.h | 14 --------
drivers/nvdimm/pfn_devs.c | 77 ++++++++-------------------------------------
include/linux/mmzone.h | 3 ++
3 files changed, 16 insertions(+), 78 deletions(-)

diff --git a/drivers/nvdimm/pfn.h b/drivers/nvdimm/pfn.h
index e901e3a3b04c..cc042a98758f 100644
--- a/drivers/nvdimm/pfn.h
+++ b/drivers/nvdimm/pfn.h
@@ -41,18 +41,4 @@ struct nd_pfn_sb {
__le64 checksum;
};

-#ifdef CONFIG_SPARSEMEM
-#define PFN_SECTION_ALIGN_DOWN(x) SECTION_ALIGN_DOWN(x)
-#define PFN_SECTION_ALIGN_UP(x) SECTION_ALIGN_UP(x)
-#else
-/*
- * In this case ZONE_DEVICE=n and we will disable 'pfn' device support,
- * but we still want pmem to compile.
- */
-#define PFN_SECTION_ALIGN_DOWN(x) (x)
-#define PFN_SECTION_ALIGN_UP(x) (x)
-#endif
-
-#define PHYS_SECTION_ALIGN_DOWN(x) PFN_PHYS(PFN_SECTION_ALIGN_DOWN(PHYS_PFN(x)))
-#define PHYS_SECTION_ALIGN_UP(x) PFN_PHYS(PFN_SECTION_ALIGN_UP(PHYS_PFN(x)))
#endif /* __NVDIMM_PFN_H */
diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c
index a2406253eb70..7f54374b082f 100644
--- a/drivers/nvdimm/pfn_devs.c
+++ b/drivers/nvdimm/pfn_devs.c
@@ -595,14 +595,14 @@ static u32 info_block_reserve(void)
}

/*
- * We hotplug memory at section granularity, pad the reserved area from
- * the previous section base to the namespace base address.
+ * We hotplug memory at sub-section granularity, pad the reserved area
+ * from the previous section base to the namespace base address.
*/
static unsigned long init_altmap_base(resource_size_t base)
{
unsigned long base_pfn = PHYS_PFN(base);

- return PFN_SECTION_ALIGN_DOWN(base_pfn);
+ return SUBSECTION_ALIGN_DOWN(base_pfn);
}

static unsigned long init_altmap_reserve(resource_size_t base)
@@ -610,7 +610,7 @@ static unsigned long init_altmap_reserve(resource_size_t base)
unsigned long reserve = info_block_reserve() >> PAGE_SHIFT;
unsigned long base_pfn = PHYS_PFN(base);

- reserve += base_pfn - PFN_SECTION_ALIGN_DOWN(base_pfn);
+ reserve += base_pfn - SUBSECTION_ALIGN_DOWN(base_pfn);
return reserve;
}

@@ -641,8 +641,7 @@ static int __nvdimm_setup_pfn(struct nd_pfn *nd_pfn, struct dev_pagemap *pgmap)
nd_pfn->npfns = le64_to_cpu(pfn_sb->npfns);
pgmap->altmap_valid = false;
} else if (nd_pfn->mode == PFN_MODE_PMEM) {
- nd_pfn->npfns = PFN_SECTION_ALIGN_UP((resource_size(res)
- - offset) / PAGE_SIZE);
+ nd_pfn->npfns = PHYS_PFN((resource_size(res) - offset));
if (le64_to_cpu(nd_pfn->pfn_sb->npfns) > nd_pfn->npfns)
dev_info(&nd_pfn->dev,
"number of pfns truncated from %lld to %ld\n",
@@ -658,54 +657,14 @@ static int __nvdimm_setup_pfn(struct nd_pfn *nd_pfn, struct dev_pagemap *pgmap)
return 0;
}

-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));
-}
-
-/*
- * Check if pmem collides with 'System RAM', or other regions when
- * section aligned. Trim it accordingly.
- */
-static void trim_pfn_device(struct nd_pfn *nd_pfn, u32 *start_pad, u32 *end_trunc)
-{
- struct nd_namespace_common *ndns = nd_pfn->ndns;
- struct nd_namespace_io *nsio = to_nd_namespace_io(&ndns->dev);
- struct nd_region *nd_region = to_nd_region(nd_pfn->dev.parent);
- const resource_size_t start = nsio->res.start;
- const resource_size_t end = start + resource_size(&nsio->res);
- resource_size_t adjust, size;
-
- *start_pad = 0;
- *end_trunc = 0;
-
- adjust = start - PHYS_SECTION_ALIGN_DOWN(start);
- size = resource_size(&nsio->res) + adjust;
- if (region_intersects(start - adjust, size, IORESOURCE_SYSTEM_RAM,
- IORES_DESC_NONE) == REGION_MIXED
- || nd_region_conflict(nd_region, start - adjust, size))
- *start_pad = PHYS_SECTION_ALIGN_UP(start) - start;
-
- /* Now check that end of the range does not collide. */
- adjust = PHYS_SECTION_ALIGN_UP(end) - end;
- size = resource_size(&nsio->res) + adjust;
- if (region_intersects(start, size, IORESOURCE_SYSTEM_RAM,
- IORES_DESC_NONE) == REGION_MIXED
- || !IS_ALIGNED(end, nd_pfn->align)
- || nd_region_conflict(nd_region, start, size))
- *end_trunc = end - phys_pmem_align_down(nd_pfn, end);
-}
-
static int nd_pfn_init(struct nd_pfn *nd_pfn)
{
struct nd_namespace_common *ndns = nd_pfn->ndns;
struct nd_namespace_io *nsio = to_nd_namespace_io(&ndns->dev);
- u32 start_pad, end_trunc, reserve = info_block_reserve();
resource_size_t start, size;
struct nd_region *nd_region;
+ unsigned long npfns, align;
struct nd_pfn_sb *pfn_sb;
- unsigned long npfns;
phys_addr_t offset;
const char *sig;
u64 checksum;
@@ -736,43 +695,35 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
return -ENXIO;
}

- memset(pfn_sb, 0, sizeof(*pfn_sb));
-
- trim_pfn_device(nd_pfn, &start_pad, &end_trunc);
- if (start_pad + end_trunc)
- dev_info(&nd_pfn->dev, "%s alignment collision, truncate %d bytes\n",
- dev_name(&ndns->dev), start_pad + end_trunc);
-
/*
* Note, we use 64 here for the standard size of struct page,
* debugging options may cause it to be larger in which case the
* implementation will limit the pfns advertised through
* ->direct_access() to those that are included in the memmap.
*/
- start = nsio->res.start + start_pad;
+ start = nsio->res.start;
size = resource_size(&nsio->res);
- npfns = PFN_SECTION_ALIGN_UP((size - start_pad - end_trunc - reserve)
- / PAGE_SIZE);
+ npfns = PHYS_PFN(size - SZ_8K);
+ align = max(nd_pfn->align, (1UL << SUBSECTION_SHIFT));
if (nd_pfn->mode == PFN_MODE_PMEM) {
/*
* The altmap should be padded out to the block size used
* when populating the vmemmap. This *should* be equal to
* PMD_SIZE for most architectures.
*/
- offset = ALIGN(start + reserve + 64 * npfns,
- max(nd_pfn->align, PMD_SIZE)) - start;
+ offset = ALIGN(start + SZ_8K + 64 * npfns, align) - start;
} else if (nd_pfn->mode == PFN_MODE_RAM)
- offset = ALIGN(start + reserve, nd_pfn->align) - start;
+ offset = ALIGN(start + SZ_8K, align) - start;
else
return -ENXIO;

- if (offset + start_pad + end_trunc >= size) {
+ if (offset >= size) {
dev_err(&nd_pfn->dev, "%s unable to satisfy requested alignment\n",
dev_name(&ndns->dev));
return -ENXIO;
}

- npfns = (size - offset - start_pad - end_trunc) / SZ_4K;
+ npfns = PHYS_PFN(size - offset);
pfn_sb->mode = cpu_to_le32(nd_pfn->mode);
pfn_sb->dataoff = cpu_to_le64(offset);
pfn_sb->npfns = cpu_to_le64(npfns);
@@ -781,8 +732,6 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
memcpy(pfn_sb->parent_uuid, nd_dev_to_uuid(&ndns->dev), 16);
pfn_sb->version_major = cpu_to_le16(1);
pfn_sb->version_minor = cpu_to_le16(3);
- pfn_sb->start_pad = cpu_to_le32(start_pad);
- pfn_sb->end_trunc = cpu_to_le32(end_trunc);
pfn_sb->align = cpu_to_le32(nd_pfn->align);
checksum = nd_sb_checksum((struct nd_gen_sb *) pfn_sb);
pfn_sb->checksum = cpu_to_le64(checksum);
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 49e7fb452dfd..15e07f007ba2 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1181,6 +1181,9 @@ static inline unsigned long section_nr_to_pfn(unsigned long sec)
#define SUBSECTIONS_PER_SECTION (1UL << (SECTION_SIZE_BITS - SUBSECTION_SHIFT))
#endif

+#define SUBSECTION_ALIGN_UP(pfn) ALIGN((pfn), PAGES_PER_SUBSECTION)
+#define SUBSECTION_ALIGN_DOWN(pfn) ((pfn) & PAGE_SUBSECTION_MASK)
+
struct mem_section_usage {
DECLARE_BITMAP(subsection_map, SUBSECTIONS_PER_SECTION);
/* See declaration of similar field in struct zone */
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