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    Subject[PATCH v2 15/22] device-dax: Add an allocation interface for device-dax instances
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    Date
    In preparation for a facility that enables dax regions to be
    sub-divided, introduce infrastructure to track and allocate region
    capacity.

    The new dax_region/available_size attribute is only enabled for volatile
    hmem devices, not pmem devices that are defined by nvdimm namespace
    boundaries. This is per Jeff's feedback the last time dynamic device-dax
    capacity allocation support was discussed.

    Link: https://lore.kernel.org/linux-nvdimm/x49shpp3zn8.fsf@segfault.boston.devel.redhat.com
    Cc: Vishal Verma <vishal.l.verma@intel.com>
    Signed-off-by: Dan Williams <dan.j.williams@intel.com>
    ---
    drivers/dax/bus.c | 120 +++++++++++++++++++++++++++++++++++++++++----
    drivers/dax/bus.h | 7 ++-
    drivers/dax/dax-private.h | 2 -
    drivers/dax/hmem/hmem.c | 7 +--
    drivers/dax/pmem/core.c | 8 +--
    5 files changed, 121 insertions(+), 23 deletions(-)

    diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
    index 96bd64ba95a5..0a48ce378686 100644
    --- a/drivers/dax/bus.c
    +++ b/drivers/dax/bus.c
    @@ -130,6 +130,11 @@ ATTRIBUTE_GROUPS(dax_drv);

    static int dax_bus_match(struct device *dev, struct device_driver *drv);

    +static bool is_static(struct dax_region *dax_region)
    +{
    + return (dax_region->res.flags & IORESOURCE_DAX_STATIC) != 0;
    +}
    +
    static struct bus_type dax_bus_type = {
    .name = "dax",
    .uevent = dax_bus_uevent,
    @@ -185,7 +190,48 @@ static ssize_t align_show(struct device *dev,
    }
    static DEVICE_ATTR_RO(align);

    +#define for_each_dax_region_resource(dax_region, res) \
    + for (res = (dax_region)->res.child; res; res = res->sibling)
    +
    +static unsigned long long dax_region_avail_size(struct dax_region *dax_region)
    +{
    + resource_size_t size = resource_size(&dax_region->res);
    + struct resource *res;
    +
    + device_lock_assert(dax_region->dev);
    +
    + for_each_dax_region_resource(dax_region, res)
    + size -= resource_size(res);
    + return size;
    +}
    +
    +static ssize_t available_size_show(struct device *dev,
    + struct device_attribute *attr, char *buf)
    +{
    + struct dax_region *dax_region = dev_get_drvdata(dev);
    + unsigned long long size;
    +
    + device_lock(dev);
    + size = dax_region_avail_size(dax_region);
    + device_unlock(dev);
    +
    + return sprintf(buf, "%llu\n", size);
    +}
    +static DEVICE_ATTR_RO(available_size);
    +
    +static umode_t dax_region_visible(struct kobject *kobj, struct attribute *a,
    + int n)
    +{
    + struct device *dev = container_of(kobj, struct device, kobj);
    + struct dax_region *dax_region = dev_get_drvdata(dev);
    +
    + if (is_static(dax_region) && a == &dev_attr_available_size.attr)
    + return 0;
    + return a->mode;
    +}
    +
    static struct attribute *dax_region_attributes[] = {
    + &dev_attr_available_size.attr,
    &dev_attr_region_size.attr,
    &dev_attr_align.attr,
    &dev_attr_id.attr,
    @@ -195,6 +241,7 @@ static struct attribute *dax_region_attributes[] = {
    static const struct attribute_group dax_region_attribute_group = {
    .name = "dax_region",
    .attrs = dax_region_attributes,
    + .is_visible = dax_region_visible,
    };

    static const struct attribute_group *dax_region_attribute_groups[] = {
    @@ -226,7 +273,8 @@ static void dax_region_unregister(void *region)
    }

    struct dax_region *alloc_dax_region(struct device *parent, int region_id,
    - struct resource *res, int target_node, unsigned int align)
    + struct resource *res, int target_node, unsigned int align,
    + unsigned long flags)
    {
    struct dax_region *dax_region;

    @@ -249,12 +297,17 @@ struct dax_region *alloc_dax_region(struct device *parent, int region_id,
    return NULL;

    dev_set_drvdata(parent, dax_region);
    - memcpy(&dax_region->res, res, sizeof(*res));
    kref_init(&dax_region->kref);
    dax_region->id = region_id;
    dax_region->align = align;
    dax_region->dev = parent;
    dax_region->target_node = target_node;
    + dax_region->res = (struct resource) {
    + .start = res->start,
    + .end = res->end,
    + .flags = IORESOURCE_MEM | flags,
    + };
    +
    if (sysfs_create_groups(&parent->kobj, dax_region_attribute_groups)) {
    kfree(dax_region);
    return NULL;
    @@ -267,6 +320,32 @@ struct dax_region *alloc_dax_region(struct device *parent, int region_id,
    }
    EXPORT_SYMBOL_GPL(alloc_dax_region);

    +static int alloc_dev_dax_range(struct dev_dax *dev_dax, resource_size_t size)
    +{
    + struct dax_region *dax_region = dev_dax->region;
    + struct resource *res = &dax_region->res;
    + struct device *dev = &dev_dax->dev;
    + struct resource *alloc;
    +
    + device_lock_assert(dax_region->dev);
    +
    + /* TODO: handle multiple allocations per region */
    + if (res->child)
    + return -ENOMEM;
    +
    + alloc = __request_region(res, res->start, size, dev_name(dev), 0);
    +
    + if (!alloc)
    + return -ENOMEM;
    +
    + dev_dax->range = (struct range) {
    + .start = alloc->start,
    + .end = alloc->end,
    + };
    +
    + return 0;
    +}
    +
    static ssize_t size_show(struct device *dev,
    struct device_attribute *attr, char *buf)
    {
    @@ -361,6 +440,15 @@ void kill_dev_dax(struct dev_dax *dev_dax)
    }
    EXPORT_SYMBOL_GPL(kill_dev_dax);

    +static void free_dev_dax_range(struct dev_dax *dev_dax)
    +{
    + struct dax_region *dax_region = dev_dax->region;
    + struct range *range = &dev_dax->range;
    +
    + device_lock_assert(dax_region->dev);
    + __release_region(&dax_region->res, range->start, range_len(range));
    +}
    +
    static void dev_dax_release(struct device *dev)
    {
    struct dev_dax *dev_dax = to_dev_dax(dev);
    @@ -385,6 +473,7 @@ static void unregister_dev_dax(void *dev)
    dev_dbg(dev, "%s\n", __func__);

    kill_dev_dax(dev_dax);
    + free_dev_dax_range(dev_dax);
    device_del(dev);
    put_device(dev);
    }
    @@ -397,7 +486,7 @@ struct dev_dax *devm_create_dev_dax(struct dev_dax_data *data)
    struct dev_dax *dev_dax;
    struct inode *inode;
    struct device *dev;
    - int rc = -ENOMEM;
    + int rc;

    if (data->id < 0)
    return ERR_PTR(-EINVAL);
    @@ -406,11 +495,25 @@ struct dev_dax *devm_create_dev_dax(struct dev_dax_data *data)
    if (!dev_dax)
    return ERR_PTR(-ENOMEM);

    + dev_dax->region = dax_region;
    + dev = &dev_dax->dev;
    + device_initialize(dev);
    + dev_set_name(dev, "dax%d.%d", dax_region->id, data->id);
    +
    + rc = alloc_dev_dax_range(dev_dax, data->size);
    + if (rc)
    + goto err_range;
    +
    if (data->pgmap) {
    + dev_WARN_ONCE(parent, !is_static(dax_region),
    + "custom dev_pagemap requires a static dax_region\n");
    +
    dev_dax->pgmap = kmemdup(data->pgmap,
    sizeof(struct dev_pagemap), GFP_KERNEL);
    - if (!dev_dax->pgmap)
    + if (!dev_dax->pgmap) {
    + rc = -ENOMEM;
    goto err_pgmap;
    + }
    }

    /*
    @@ -427,12 +530,7 @@ struct dev_dax *devm_create_dev_dax(struct dev_dax_data *data)
    kill_dax(dax_dev);

    /* from here on we're committed to teardown via dev_dax_release() */
    - dev = &dev_dax->dev;
    - device_initialize(dev);
    -
    dev_dax->dax_dev = dax_dev;
    - dev_dax->region = dax_region;
    - dev_dax->range = data->range;
    dev_dax->target_node = dax_region->target_node;
    kref_get(&dax_region->kref);

    @@ -444,7 +542,6 @@ struct dev_dax *devm_create_dev_dax(struct dev_dax_data *data)
    dev->class = dax_class;
    dev->parent = parent;
    dev->type = &dev_dax_type;
    - dev_set_name(dev, "dax%d.%d", dax_region->id, data->id);

    rc = device_add(dev);
    if (rc) {
    @@ -458,9 +555,12 @@ struct dev_dax *devm_create_dev_dax(struct dev_dax_data *data)
    return ERR_PTR(rc);

    return dev_dax;
    +
    err_alloc_dax:
    kfree(dev_dax->pgmap);
    err_pgmap:
    + free_dev_dax_range(dev_dax);
    +err_range:
    kfree(dev_dax);

    return ERR_PTR(rc);
    diff --git a/drivers/dax/bus.h b/drivers/dax/bus.h
    index 4aeb36da83a4..44592a8cac0f 100644
    --- a/drivers/dax/bus.h
    +++ b/drivers/dax/bus.h
    @@ -10,8 +10,11 @@ struct resource;
    struct dax_device;
    struct dax_region;
    void dax_region_put(struct dax_region *dax_region);
    +
    +#define IORESOURCE_DAX_STATIC (1UL << 0)
    struct dax_region *alloc_dax_region(struct device *parent, int region_id,
    - struct resource *res, int target_node, unsigned int align);
    + struct resource *res, int target_node, unsigned int align,
    + unsigned long flags);

    enum dev_dax_subsys {
    DEV_DAX_BUS = 0, /* zeroed dev_dax_data picks this by default */
    @@ -22,7 +25,7 @@ struct dev_dax_data {
    struct dax_region *dax_region;
    struct dev_pagemap *pgmap;
    enum dev_dax_subsys subsys;
    - struct range range;
    + resource_size_t size;
    int id;
    };

    diff --git a/drivers/dax/dax-private.h b/drivers/dax/dax-private.h
    index 12a2dbc43b40..99b1273bb232 100644
    --- a/drivers/dax/dax-private.h
    +++ b/drivers/dax/dax-private.h
    @@ -22,7 +22,7 @@ void dax_bus_exit(void);
    * @kref: to pin while other agents have a need to do lookups
    * @dev: parent device backing this region
    * @align: allocation and mapping alignment for child dax devices
    - * @res: physical address range of the region
    + * @res: resource tree to track instance allocations
    */
    struct dax_region {
    int id;
    diff --git a/drivers/dax/hmem/hmem.c b/drivers/dax/hmem/hmem.c
    index af82d6ba820a..e7b64539e23e 100644
    --- a/drivers/dax/hmem/hmem.c
    +++ b/drivers/dax/hmem/hmem.c
    @@ -20,17 +20,14 @@ static int dax_hmem_probe(struct platform_device *pdev)

    mri = dev->platform_data;
    dax_region = alloc_dax_region(dev, pdev->id, res, mri->target_node,
    - PMD_SIZE);
    + PMD_SIZE, 0);
    if (!dax_region)
    return -ENOMEM;

    data = (struct dev_dax_data) {
    .dax_region = dax_region,
    .id = 0,
    - .range = {
    - .start = res->start,
    - .end = res->end,
    - },
    + .size = resource_size(res),
    };
    dev_dax = devm_create_dev_dax(&data);
    if (IS_ERR(dev_dax))
    diff --git a/drivers/dax/pmem/core.c b/drivers/dax/pmem/core.c
    index 4fa81d3d2f65..4fe700884338 100644
    --- a/drivers/dax/pmem/core.c
    +++ b/drivers/dax/pmem/core.c
    @@ -54,7 +54,8 @@ struct dev_dax *__dax_pmem_probe(struct device *dev, enum dev_dax_subsys subsys)
    memcpy(&res, &pgmap.res, sizeof(res));
    res.start += offset;
    dax_region = alloc_dax_region(dev, region_id, &res,
    - nd_region->target_node, le32_to_cpu(pfn_sb->align));
    + nd_region->target_node, le32_to_cpu(pfn_sb->align),
    + IORESOURCE_DAX_STATIC);
    if (!dax_region)
    return ERR_PTR(-ENOMEM);

    @@ -63,10 +64,7 @@ struct dev_dax *__dax_pmem_probe(struct device *dev, enum dev_dax_subsys subsys)
    .id = id,
    .pgmap = &pgmap,
    .subsys = subsys,
    - .range = {
    - .start = res.start,
    - .end = res.end,
    - },
    + .size = resource_size(&res),
    };
    dev_dax = devm_create_dev_dax(&data);

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