libnvdimm/region: Introduce an 'align' attribute

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>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Reviewed-by: Jeff Moyer <jmoyer@redhat.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>

diff --git a/drivers/nvdimm/dimm_devs.c b/drivers/nvdimm/dimm_devs.c
index 39a61a5..b7b77e8 100644 (file)
--- 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 01f6c22..ae155e8 100644 (file)
--- a/drivers/nvdimm/namespace_devs.c
+++ b/drivers/nvdimm/namespace_devs.c
@@ -542,6 +542,11 @@ 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;
@@ -981,10 +986,10 @@ 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 ca39abe..c4d69c1 100644 (file)
--- 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 a5fc6e4..bf239e7 100644 (file)
--- 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