Re: [PATCH 5/5] libnvdimm/region: Introduce an 'align' attribute
From: Aneesh Kumar K.V
Date: Mon Feb 03 2020 - 12:10:51 EST
Dan Williams <dan.j.williams@xxxxxxxxx> writes:
> 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.
>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
> Reported-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
> Reported-by: Jeff Moyer <jmoyer@xxxxxxxxxx>
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> ---
> 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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