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Subject[PATCH v2 4/4] libnvdimm/region: Introduce an 'align' attribute
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The align attribute applies an alignment constraint for namespace
creation in a region. Whereas the 'align' attribute of a namespace
applied alignment padding via an info block, the 'align' attribute
applies alignment constraints to the free space allocation.

The default for 'align' is the maximum known memremap_compat_align()
across all archs (16MiB from PowerPC at time of writing) multiplied by
the number of interleave ways if there is blk-aliasing. The minimum is
PAGE_SIZE and allows for the creation of cross-arch incompatible
namespaces, just as previous kernels allowed, but the expectation is
cross-arch and mode-independent compatibility by default.

The regression risk with this change is limited to cases that were
dependent on the ability to create unaligned namespaces, *and* for some
reason are unable to opt-out of aligned namespaces by writing to
'regionX/align'. If such a scenario arises the default can be flipped
from opt-out to opt-in of compat-aligned namespace creation, but that is
a last resort. The kernel will otherwise continue to support existing
defined misaligned namespaces.

Unfortunately this change needs to touch several parts of the
implementation at once:

- region/available_size: expand busy extents to current align
- region/max_available_extent: expand busy extents to current align
- namespace/size: trim free space to current align

...to keep the free space accounting conforming to the dynamic align
setting.

Reported-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Reported-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Link: https://lore.kernel.org/r/158041478371.3889308.14542630147672668068.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
drivers/nvdimm/dimm_devs.c | 86 +++++++++++++++++++++++----
drivers/nvdimm/namespace_devs.c | 9 ++-
drivers/nvdimm/nd.h | 1
drivers/nvdimm/region_devs.c | 122 ++++++++++++++++++++++++++++++++++++---
4 files changed, 192 insertions(+), 26 deletions(-)

diff --git a/drivers/nvdimm/dimm_devs.c b/drivers/nvdimm/dimm_devs.c
index 64159d4d4b8f..b4994abb655f 100644
--- a/drivers/nvdimm/dimm_devs.c
+++ b/drivers/nvdimm/dimm_devs.c
@@ -563,6 +563,21 @@ int nvdimm_security_freeze(struct nvdimm *nvdimm)
return rc;
}

+static unsigned long dpa_align(struct nd_region *nd_region)
+{
+ struct device *dev = &nd_region->dev;
+
+ if (dev_WARN_ONCE(dev, !is_nvdimm_bus_locked(dev),
+ "bus lock required for capacity provision\n"))
+ return 0;
+ if (dev_WARN_ONCE(dev, !nd_region->ndr_mappings || nd_region->align
+ % nd_region->ndr_mappings,
+ "invalid region align %#lx mappings: %d\n",
+ nd_region->align, nd_region->ndr_mappings))
+ return 0;
+ return nd_region->align / nd_region->ndr_mappings;
+}
+
int alias_dpa_busy(struct device *dev, void *data)
{
resource_size_t map_end, blk_start, new;
@@ -571,6 +586,7 @@ int alias_dpa_busy(struct device *dev, void *data)
struct nd_region *nd_region;
struct nvdimm_drvdata *ndd;
struct resource *res;
+ unsigned long align;
int i;

if (!is_memory(dev))
@@ -608,13 +624,21 @@ int alias_dpa_busy(struct device *dev, void *data)
* Find the free dpa from the end of the last pmem allocation to
* the end of the interleave-set mapping.
*/
+ align = dpa_align(nd_region);
+ if (!align)
+ return 0;
+
for_each_dpa_resource(ndd, res) {
+ resource_size_t start, end;
+
if (strncmp(res->name, "pmem", 4) != 0)
continue;
- if ((res->start >= blk_start && res->start < map_end)
- || (res->end >= blk_start
- && res->end <= map_end)) {
- new = max(blk_start, min(map_end + 1, res->end + 1));
+
+ start = ALIGN_DOWN(res->start, align);
+ end = ALIGN(res->end + 1, align) - 1;
+ if ((start >= blk_start && start < map_end)
+ || (end >= blk_start && end <= map_end)) {
+ new = max(blk_start, min(map_end, end) + 1);
if (new != blk_start) {
blk_start = new;
goto retry;
@@ -654,6 +678,7 @@ resource_size_t nd_blk_available_dpa(struct nd_region *nd_region)
.res = NULL,
};
struct resource *res;
+ unsigned long align;

if (!ndd)
return 0;
@@ -661,10 +686,20 @@ resource_size_t nd_blk_available_dpa(struct nd_region *nd_region)
device_for_each_child(&nvdimm_bus->dev, &info, alias_dpa_busy);

/* now account for busy blk allocations in unaliased dpa */
+ align = dpa_align(nd_region);
+ if (!align)
+ return 0;
for_each_dpa_resource(ndd, res) {
+ resource_size_t start, end, size;
+
if (strncmp(res->name, "blk", 3) != 0)
continue;
- info.available -= resource_size(res);
+ start = ALIGN_DOWN(res->start, align);
+ end = ALIGN(res->end + 1, align) - 1;
+ size = end - start + 1;
+ if (size >= info.available)
+ return 0;
+ info.available -= size;
}

return info.available;
@@ -683,19 +718,31 @@ resource_size_t nd_pmem_max_contiguous_dpa(struct nd_region *nd_region,
struct nvdimm_bus *nvdimm_bus;
resource_size_t max = 0;
struct resource *res;
+ unsigned long align;

/* if a dimm is disabled the available capacity is zero */
if (!ndd)
return 0;

+ align = dpa_align(nd_region);
+ if (!align)
+ return 0;
+
nvdimm_bus = walk_to_nvdimm_bus(ndd->dev);
if (__reserve_free_pmem(&nd_region->dev, nd_mapping->nvdimm))
return 0;
for_each_dpa_resource(ndd, res) {
+ resource_size_t start, end;
+
if (strcmp(res->name, "pmem-reserve") != 0)
continue;
- if (resource_size(res) > max)
- max = resource_size(res);
+ /* trim free space relative to current alignment setting */
+ start = ALIGN(res->start, align);
+ end = ALIGN_DOWN(res->end + 1, align) - 1;
+ if (end < start)
+ continue;
+ if (end - start + 1 > max)
+ max = end - start + 1;
}
release_free_pmem(nvdimm_bus, nd_mapping);
return max;
@@ -723,24 +770,33 @@ resource_size_t nd_pmem_available_dpa(struct nd_region *nd_region,
struct nvdimm_drvdata *ndd = to_ndd(nd_mapping);
struct resource *res;
const char *reason;
+ unsigned long align;

if (!ndd)
return 0;

+ align = dpa_align(nd_region);
+ if (!align)
+ return 0;
+
map_start = nd_mapping->start;
map_end = map_start + nd_mapping->size - 1;
blk_start = max(map_start, map_end + 1 - *overlap);
for_each_dpa_resource(ndd, res) {
- if (res->start >= map_start && res->start < map_end) {
+ resource_size_t start, end;
+
+ start = ALIGN_DOWN(res->start, align);
+ end = ALIGN(res->end + 1, align) - 1;
+ if (start >= map_start && start < map_end) {
if (strncmp(res->name, "blk", 3) == 0)
blk_start = min(blk_start,
- max(map_start, res->start));
- else if (res->end > map_end) {
+ max(map_start, start));
+ else if (end > map_end) {
reason = "misaligned to iset";
goto err;
} else
- busy += resource_size(res);
- } else if (res->end >= map_start && res->end <= map_end) {
+ busy += end - start + 1;
+ } else if (end >= map_start && end <= map_end) {
if (strncmp(res->name, "blk", 3) == 0) {
/*
* If a BLK allocation overlaps the start of
@@ -749,8 +805,8 @@ resource_size_t nd_pmem_available_dpa(struct nd_region *nd_region,
*/
blk_start = map_start;
} else
- busy += resource_size(res);
- } else if (map_start > res->start && map_start < res->end) {
+ busy += end - start + 1;
+ } else if (map_start > start && map_start < end) {
/* total eclipse of the mapping */
busy += nd_mapping->size;
blk_start = map_start;
@@ -760,7 +816,7 @@ resource_size_t nd_pmem_available_dpa(struct nd_region *nd_region,
*overlap = map_end + 1 - blk_start;
available = blk_start - map_start;
if (busy < available)
- return available - busy;
+ return ALIGN_DOWN(available - busy, align);
return 0;

err:
diff --git a/drivers/nvdimm/namespace_devs.c b/drivers/nvdimm/namespace_devs.c
index 30cda9f235de..4720ad69e1c5 100644
--- a/drivers/nvdimm/namespace_devs.c
+++ b/drivers/nvdimm/namespace_devs.c
@@ -541,6 +541,11 @@ static void space_valid(struct nd_region *nd_region, struct nvdimm_drvdata *ndd,
{
bool is_reserve = strcmp(label_id->id, "pmem-reserve") == 0;
bool is_pmem = strncmp(label_id->id, "pmem", 4) == 0;
+ unsigned long align;
+
+ align = nd_region->align / nd_region->ndr_mappings;
+ valid->start = ALIGN(valid->start, align);
+ valid->end = ALIGN_DOWN(valid->end + 1, align) - 1;

if (valid->start >= valid->end)
goto invalid;
@@ -980,10 +985,10 @@ static ssize_t __size_store(struct device *dev, unsigned long long val)
return -ENXIO;
}

- div_u64_rem(val, PAGE_SIZE * nd_region->ndr_mappings, &remainder);
+ div_u64_rem(val, nd_region->align, &remainder);
if (remainder) {
dev_dbg(dev, "%llu is not %ldK aligned\n", val,
- (PAGE_SIZE * nd_region->ndr_mappings) / SZ_1K);
+ nd_region->align / SZ_1K);
return -EINVAL;
}

diff --git a/drivers/nvdimm/nd.h b/drivers/nvdimm/nd.h
index ca39abe29c7c..c4d69c1cce55 100644
--- a/drivers/nvdimm/nd.h
+++ b/drivers/nvdimm/nd.h
@@ -146,6 +146,7 @@ struct nd_region {
struct device *btt_seed;
struct device *pfn_seed;
struct device *dax_seed;
+ unsigned long align;
u16 ndr_mappings;
u64 ndr_size;
u64 ndr_start;
diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index a5fc6e4c56ff..bf239e783940 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -216,21 +216,25 @@ int nd_region_to_nstype(struct nd_region *nd_region)
}
EXPORT_SYMBOL(nd_region_to_nstype);

-static ssize_t size_show(struct device *dev,
- struct device_attribute *attr, char *buf)
+static unsigned long long region_size(struct nd_region *nd_region)
{
- struct nd_region *nd_region = to_nd_region(dev);
- unsigned long long size = 0;
-
- if (is_memory(dev)) {
- size = nd_region->ndr_size;
+ if (is_memory(&nd_region->dev)) {
+ return nd_region->ndr_size;
} else if (nd_region->ndr_mappings == 1) {
struct nd_mapping *nd_mapping = &nd_region->mapping[0];

- size = nd_mapping->size;
+ return nd_mapping->size;
}

- return sprintf(buf, "%llu\n", size);
+ return 0;
+}
+
+static ssize_t size_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct nd_region *nd_region = to_nd_region(dev);
+
+ return sprintf(buf, "%llu\n", region_size(nd_region));
}
static DEVICE_ATTR_RO(size);

@@ -529,6 +533,55 @@ static ssize_t read_only_store(struct device *dev,
}
static DEVICE_ATTR_RW(read_only);

+static ssize_t align_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct nd_region *nd_region = to_nd_region(dev);
+
+ return sprintf(buf, "%#lx\n", nd_region->align);
+}
+
+static ssize_t align_store(struct device *dev,
+ struct device_attribute *attr, const char *buf, size_t len)
+{
+ struct nd_region *nd_region = to_nd_region(dev);
+ unsigned long val, dpa;
+ u32 remainder;
+ int rc;
+
+ rc = kstrtoul(buf, 0, &val);
+ if (rc)
+ return rc;
+
+ if (!nd_region->ndr_mappings)
+ return -ENXIO;
+
+ /*
+ * Ensure space-align is evenly divisible by the region
+ * interleave-width because the kernel typically has no facility
+ * to determine which DIMM(s), dimm-physical-addresses, would
+ * contribute to the tail capacity in system-physical-address
+ * space for the namespace.
+ */
+ dpa = val;
+ remainder = do_div(dpa, nd_region->ndr_mappings);
+ if (!is_power_of_2(dpa) || dpa < PAGE_SIZE
+ || val > region_size(nd_region) || remainder)
+ return -EINVAL;
+
+ /*
+ * Given that space allocation consults this value multiple
+ * times ensure it does not change for the duration of the
+ * allocation.
+ */
+ nvdimm_bus_lock(dev);
+ nd_region->align = val;
+ nvdimm_bus_unlock(dev);
+
+ return len;
+}
+static DEVICE_ATTR_RW(align);
+
static ssize_t region_badblocks_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
@@ -571,6 +624,7 @@ static DEVICE_ATTR_RO(persistence_domain);

static struct attribute *nd_region_attributes[] = {
&dev_attr_size.attr,
+ &dev_attr_align.attr,
&dev_attr_nstype.attr,
&dev_attr_mappings.attr,
&dev_attr_btt_seed.attr,
@@ -626,6 +680,19 @@ static umode_t region_visible(struct kobject *kobj, struct attribute *a, int n)
return a->mode;
}

+ if (a == &dev_attr_align.attr) {
+ int i;
+
+ for (i = 0; i < nd_region->ndr_mappings; i++) {
+ struct nd_mapping *nd_mapping = &nd_region->mapping[i];
+ struct nvdimm *nvdimm = nd_mapping->nvdimm;
+
+ if (test_bit(NDD_LABELING, &nvdimm->flags))
+ return a->mode;
+ }
+ return 0;
+ }
+
if (a != &dev_attr_set_cookie.attr
&& a != &dev_attr_available_size.attr)
return a->mode;
@@ -935,6 +1002,42 @@ void nd_region_release_lane(struct nd_region *nd_region, unsigned int lane)
}
EXPORT_SYMBOL(nd_region_release_lane);

+/*
+ * PowerPC requires this alignment for memremap_pages(). All other archs
+ * should be ok with SUBSECTION_SIZE (see memremap_compat_align()).
+ */
+#define MEMREMAP_COMPAT_ALIGN_MAX SZ_16M
+
+static unsigned long default_align(struct nd_region *nd_region)
+{
+ unsigned long align, per_mapping;
+ int i, mappings;
+ u32 remainder;
+
+ if (is_nd_blk(&nd_region->dev))
+ align = PAGE_SIZE;
+ else
+ align = MEMREMAP_COMPAT_ALIGN_MAX;
+
+ for (i = 0; i < nd_region->ndr_mappings; i++) {
+ struct nd_mapping *nd_mapping = &nd_region->mapping[i];
+ struct nvdimm *nvdimm = nd_mapping->nvdimm;
+
+ if (test_bit(NDD_ALIASING, &nvdimm->flags)) {
+ align = MEMREMAP_COMPAT_ALIGN_MAX;
+ break;
+ }
+ }
+
+ mappings = max_t(u16, 1, nd_region->ndr_mappings);
+ per_mapping = align;
+ remainder = do_div(per_mapping, mappings);
+ if (remainder)
+ align *= mappings;
+
+ return align;
+}
+
static struct nd_region *nd_region_create(struct nvdimm_bus *nvdimm_bus,
struct nd_region_desc *ndr_desc,
const struct device_type *dev_type, const char *caller)
@@ -1039,6 +1142,7 @@ static struct nd_region *nd_region_create(struct nvdimm_bus *nvdimm_bus,
dev->of_node = ndr_desc->of_node;
nd_region->ndr_size = resource_size(ndr_desc->res);
nd_region->ndr_start = ndr_desc->res->start;
+ nd_region->align = default_align(nd_region);
if (ndr_desc->flush)
nd_region->flush = ndr_desc->flush;
else
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