When an extent is accepted/released, the CXL driver must notify
the DAX driver to coordinate the management of resources. Define
the .notify callback to the cxl_dax region driver to enable
the coordination.

Define struct dax_resource, a sub-resource of a DC dax_region
representing the capacity of one dc_extent.

When the cxl side onlines a tag group during a DC Add event,
notify the DAX region to register a struct dax_resource for each
extent under the dax_region's resource tree.

The dax_resource model:

  * struct dax_resource (dax-private.h) — per-extent sub-resource of
    a DC dax_region: pointer back to its region, the kernel struct
    resource, the tag uuid, the per-allocation seq_num, and a use_cnt
    that lets a later commit refuse release of an in-use extent.
  * struct dev_dax_range gains a dax_resource back-pointer so a
    carved range remembers which extent it lives in.

For now, dax_resources live under the dax_region and remain inaccessible
to DAX devices. A later commit adds the support to specify a tag
when creating a DAX device, which then allows dax_resources to be
claimed by tag.

Release is handled in the following commit.

Based on an original patch by Navneet Singh.

Signed-off-by: Ira Weiny <[email protected]>
Signed-off-by: Anisa Su <[email protected]>

---
Changes:
[anisa:restructured from the original "Create resources on sparse DAX
 regions" commit】
---
 drivers/cxl/core/core.h   |  10 ++++
 drivers/cxl/core/extent.c |  33 ++++++++++-
 drivers/cxl/core/mbox.c   |  17 +++++-
 drivers/cxl/cxl.h         |   6 ++
 drivers/dax/bus.c         | 118 ++++++++++++++++++++++++++++++++++----
 drivers/dax/bus.h         |   3 +-
 drivers/dax/cxl.c         |  88 +++++++++++++++++++++++++++-
 drivers/dax/dax-private.h |  49 ++++++++++++++++
 drivers/dax/hmem/hmem.c   |   2 +-
 drivers/dax/pmem.c        |   2 +-
 10 files changed, 306 insertions(+), 22 deletions(-)

diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h
index 02b36728c22d..c28e357c5817 100644
--- a/drivers/cxl/core/core.h
+++ b/drivers/cxl/core/core.h
@@ -72,6 +72,9 @@ int cxl_add_extent(struct cxl_memdev_state *mds, struct 
cxl_extent *extent,
 bool cxl_tag_already_committed(const uuid_t *tag);
 int cxl_rm_extent(struct cxl_memdev_state *mds, struct cxl_extent *extent);
 int online_tag_group(struct cxl_dc_tag_group *group);
+void rm_tag_group(struct cxl_dc_tag_group *group);
+int cxlr_notify_extent(struct cxl_region *cxlr, enum dc_event event,
+                      struct cxl_dc_tag_group *group);
 #else
 static inline u64 cxl_dpa_to_hpa(struct cxl_region *cxlr,
                                 const struct cxl_memdev *cxlmd, u64 dpa)
@@ -96,6 +99,13 @@ static inline bool cxl_tag_already_committed(const uuid_t 
*tag)
 {
        return false;
 }
+static inline void rm_tag_group(struct cxl_dc_tag_group *group) { }
+static inline int cxlr_notify_extent(struct cxl_region *cxlr,
+                                    enum dc_event event,
+                                    struct cxl_dc_tag_group *group)
+{
+       return 0;
+}
 static inline
 struct cxl_region *cxl_dpa_to_region(const struct cxl_memdev *cxlmd, u64 dpa,
                                     struct cxl_endpoint_decoder **cxled)
diff --git a/drivers/cxl/core/extent.c b/drivers/cxl/core/extent.c
index 34babfe032d1..3fc4b7292664 100644
--- a/drivers/cxl/core/extent.c
+++ b/drivers/cxl/core/extent.c
@@ -63,7 +63,6 @@ static const struct attribute_group dc_extent_attribute_group 
= {
 
 __ATTRIBUTE_GROUPS(dc_extent_attribute);
 
-
 static void cxled_release_extent(struct cxl_endpoint_decoder *cxled,
                                 struct dc_extent *dc_extent)
 {
@@ -359,6 +358,36 @@ dc_extent_build(struct cxl_endpoint_decoder *cxled,
        return dc_extent;
 }
 
+int cxlr_notify_extent(struct cxl_region *cxlr, enum dc_event event,
+                      struct cxl_dc_tag_group *group)
+{
+       struct device *dev = &cxlr->cxlr_dax->dev;
+       struct cxl_notify_data notify_data;
+       struct cxl_driver *driver;
+
+       dev_dbg(dev, "Trying notify: type %d tag %pUb\n", event, &group->uuid);
+
+       guard(device)(dev);
+
+       /*
+        * The lack of a driver indicates a notification has failed.  No user
+        * space coordination was possible.
+        */
+       if (!dev->driver)
+               return 0;
+       driver = to_cxl_drv(dev->driver);
+       if (!driver->notify)
+               return 0;
+
+       notify_data = (struct cxl_notify_data) {
+               .event = event,
+               .group = group,
+       };
+
+       dev_dbg(dev, "Notify: type %d tag %pUb\n", event, &group->uuid);
+       return driver->notify(dev, &notify_data);
+}
+
 /*
  * Stage 4: insert @dc_extent into the pending tag group.  All extents in
  * one More-chain group share a UUID — enforced here as the group is
@@ -462,7 +491,7 @@ static void dc_extent_unregister(void *ext)
        device_unregister(&dc_extent->dev);
 }
 
-static void rm_tag_group(struct cxl_dc_tag_group *group)
+void rm_tag_group(struct cxl_dc_tag_group *group)
 {
        struct device *region_dev = &group->cxlr_dax->dev;
        struct dc_extent *dc_extent;
diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
index 85959dee35ea..8071c1ed1b36 100644
--- a/drivers/cxl/core/mbox.c
+++ b/drivers/cxl/core/mbox.c
@@ -1558,8 +1558,21 @@ static int cxl_add_pending(struct cxl_memdev_state *mds)
                        list_for_each_entry_safe(pos, tmp, &group, list)
                                delete_extent_node(pos);
                } else {
-                       list_splice_tail_init(&group, &accepted);
-                       total_accepted += group_cnt;
+                       rc = cxlr_notify_extent(tag_group->cxlr_dax->cxlr,
+                                               DCD_ADD_CAPACITY, tag_group);
+                       if (rc) {
+                               /*
+                                * The dax-side notification failed; tear down 
the
+                                * tag group and drop the extents so we do not
+                                * mis-report acceptance to the device.
+                                */
+                               rm_tag_group(tag_group);
+                               list_for_each_entry_safe(pos, tmp, &group, list)
+                                       delete_extent_node(pos);
+                       } else {
+                               list_splice_tail_init(&group, &accepted);
+                               total_accepted += group_cnt;
+                       }
                }
 
                mds->add_ctx.group = NULL;
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index a28e7b12a4a8..27e3046654e9 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -892,6 +892,11 @@ bool is_cxl_region(struct device *dev);
 
 extern const struct bus_type cxl_bus_type;
 
+struct cxl_notify_data {
+       enum dc_event event;
+       struct cxl_dc_tag_group *group;
+};
+
 /*
  * Note, add_dport() is expressly for the cxl_port driver. TODO: investigate a
  * type-safe driver model where probe()/remove() take the type of object 
implied
@@ -904,6 +909,7 @@ struct cxl_driver {
        void (*remove)(struct device *dev);
        struct cxl_dport *(*add_dport)(struct cxl_port *port,
                                       struct device *dport_dev);
+       int (*notify)(struct device *dev, struct cxl_notify_data *notify_data);
        struct device_driver drv;
        int id;
 };
diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index b0c2162b5e37..a6ee59f2d8a1 100644
--- a/drivers/dax/bus.c
+++ b/drivers/dax/bus.c
@@ -186,6 +186,73 @@ static bool is_dynamic(struct dax_region *dax_region)
        return (dax_region->res.flags & IORESOURCE_DAX_DCD) != 0;
 }
 
+static void __dax_release_resource(struct dax_resource *dax_resource)
+{
+       struct dax_region *dax_region = dax_resource->region;
+
+       lockdep_assert_held_write(&dax_region_rwsem);
+       dev_dbg(dax_region->dev, "Extent release resource %pr\n",
+               dax_resource->res);
+       if (dax_resource->res)
+               __release_region(&dax_region->res, dax_resource->res->start,
+                                resource_size(dax_resource->res));
+       dax_resource->res = NULL;
+}
+
+static void dax_release_resource(void *res)
+{
+       struct dax_resource *dax_resource = res;
+
+       guard(rwsem_write)(&dax_region_rwsem);
+       __dax_release_resource(dax_resource);
+       kfree(dax_resource);
+}
+
+int dax_region_add_resource(struct dax_region *dax_region,
+                           struct device *device,
+                           resource_size_t start, resource_size_t length,
+                           const uuid_t *tag, u16 seq_num)
+{
+       struct resource *new_resource;
+       int rc;
+
+       struct dax_resource *dax_resource __free(kfree) =
+                               kzalloc(sizeof(*dax_resource), GFP_KERNEL);
+       if (!dax_resource)
+               return -ENOMEM;
+
+       guard(rwsem_write)(&dax_region_rwsem);
+
+       dev_dbg(dax_region->dev, "DAX region resource %pr\n", &dax_region->res);
+       new_resource = __request_region(&dax_region->res, start, length, 
"extent", 0);
+       if (!new_resource) {
+               dev_err(dax_region->dev, "Failed to add region s:%pa l:%pa\n",
+                       &start, &length);
+               return -ENOSPC;
+       }
+
+       dev_dbg(dax_region->dev, "add resource %pr\n", new_resource);
+       dax_resource->region = dax_region;
+       dax_resource->res = new_resource;
+       dax_resource->seq_num = seq_num;
+       if (tag)
+               uuid_copy(&dax_resource->uuid, tag);
+
+       /*
+        * open code devm_add_action_or_reset() to avoid recursive write lock
+        * of dax_region_rwsem in the error case.
+        */
+       rc = devm_add_action(device, dax_release_resource, dax_resource);
+       if (rc) {
+               __dax_release_resource(dax_resource);
+               return rc;
+       }
+
+       dev_set_drvdata(device, no_free_ptr(dax_resource));
+       return 0;
+}
+EXPORT_SYMBOL_GPL(dax_region_add_resource);
+
 bool static_dev_dax(struct dev_dax *dev_dax)
 {
        return is_static(dev_dax->region);
@@ -304,14 +371,25 @@ static struct device_attribute dev_attr_region_align =
 
 static unsigned long long dax_region_avail_size(struct dax_region *dax_region)
 {
-       resource_size_t size = resource_size(&dax_region->res);
+       resource_size_t size;
        struct resource *res;
 
        lockdep_assert_held(&dax_region_rwsem);
 
-       if (is_dynamic(dax_region))
-               return 0;
+       if (is_dynamic(dax_region)) {
+               /*
+                * Children of a dynamic region are extents, claimed
+                * all-or-nothing: an extent's resource is either unclaimed (no
+                * child) or fully consumed by exactly one dax device.
+                */
+               size = 0;
+               for_each_dax_region_resource(dax_region, res)
+                       if (!res->child)
+                               size += resource_size(res);
+               return size;
+       }
 
+       size = resource_size(&dax_region->res);
        for_each_dax_region_resource(dax_region, res)
                size -= resource_size(res);
        return size;
@@ -452,15 +530,26 @@ EXPORT_SYMBOL_GPL(kill_dev_dax);
 static void trim_dev_dax_range(struct dev_dax *dev_dax)
 {
        int i = dev_dax->nr_range - 1;
-       struct range *range = &dev_dax->ranges[i].range;
+       struct dev_dax_range *dev_range = &dev_dax->ranges[i];
+       struct range *range = &dev_range->range;
        struct dax_region *dax_region = dev_dax->region;
+       struct resource *res = &dax_region->res;
 
        lockdep_assert_held_write(&dax_region_rwsem);
        dev_dbg(&dev_dax->dev, "delete range[%d]: %#llx:%#llx\n", i,
                (unsigned long long)range->start,
                (unsigned long long)range->end);
 
-       __release_region(&dax_region->res, range->start, range_len(range));
+       if (dev_range->dax_resource) {
+               res = dev_range->dax_resource->res;
+               dev_dbg(&dev_dax->dev, "Trim dc extent %pr\n", res);
+       }
+
+       __release_region(res, range->start, range_len(range));
+
+       if (dev_range->dax_resource)
+               dev_range->dax_resource->use_cnt--;
+
        if (--dev_dax->nr_range == 0) {
                kfree(dev_dax->ranges);
                dev_dax->ranges = NULL;
@@ -644,11 +733,14 @@ static void dax_region_unregister(void *region)
 
 struct dax_region *alloc_dax_region(struct device *parent, int region_id,
                struct range *range, int target_node, unsigned int align,
-               unsigned long flags)
+               unsigned long flags, struct dax_dc_ops *dc_ops)
 {
        struct dax_region *dax_region;
        int rc;
 
+       if (!dc_ops && (flags & IORESOURCE_DAX_DCD))
+               return NULL;
+
        /*
         * The DAX core assumes that it can store its private data in
         * parent->driver_data. This WARN is a reminder / safeguard for
@@ -673,6 +765,7 @@ struct dax_region *alloc_dax_region(struct device *parent, 
int region_id,
        dax_region->align = align;
        dax_region->dev = parent;
        dax_region->target_node = target_node;
+       dax_region->dc_ops = dc_ops;
        ida_init(&dax_region->ida);
        dax_region->res = (struct resource) {
                .start = range->start,
@@ -861,7 +954,7 @@ static int devm_register_dax_mapping(struct dev_dax 
*dev_dax, int range_id)
 }
 
 static int alloc_dev_dax_range(struct dev_dax *dev_dax, u64 start,
-               resource_size_t size)
+               resource_size_t size, struct dax_resource *dax_resource)
 {
        struct dax_region *dax_region = dev_dax->region;
        struct resource *res = &dax_region->res;
@@ -902,6 +995,7 @@ static int alloc_dev_dax_range(struct dev_dax *dev_dax, u64 
start,
                        .start = alloc->start,
                        .end = alloc->end,
                },
+               .dax_resource = dax_resource,
        };
 
        dev_dbg(dev, "alloc range[%d]: %pa:%pa\n", dev_dax->nr_range - 1,
@@ -1075,7 +1169,7 @@ static ssize_t dev_dax_resize(struct dax_region 
*dax_region,
 retry:
        first = region_res->child;
        if (!first)
-               return alloc_dev_dax_range(dev_dax, dax_region->res.start, 
to_alloc);
+               return alloc_dev_dax_range(dev_dax, dax_region->res.start, 
to_alloc, NULL);
 
        rc = -ENOSPC;
        for (res = first; res; res = res->sibling) {
@@ -1084,7 +1178,7 @@ static ssize_t dev_dax_resize(struct dax_region 
*dax_region,
                /* space at the beginning of the region */
                if (res == first && res->start > dax_region->res.start) {
                        alloc = min(res->start - dax_region->res.start, 
to_alloc);
-                       rc = alloc_dev_dax_range(dev_dax, 
dax_region->res.start, alloc);
+                       rc = alloc_dev_dax_range(dev_dax, 
dax_region->res.start, alloc, NULL);
                        break;
                }
 
@@ -1104,7 +1198,7 @@ static ssize_t dev_dax_resize(struct dax_region 
*dax_region,
                        rc = adjust_dev_dax_range(dev_dax, res, 
resource_size(res) + alloc);
                        break;
                }
-               rc = alloc_dev_dax_range(dev_dax, res->end + 1, alloc);
+               rc = alloc_dev_dax_range(dev_dax, res->end + 1, alloc, NULL);
                break;
        }
        if (rc)
@@ -1214,7 +1308,7 @@ static ssize_t mapping_store(struct device *dev, struct 
device_attribute *attr,
 
        to_alloc = range_len(&r);
        if (alloc_is_aligned(dev_dax, to_alloc))
-               rc = alloc_dev_dax_range(dev_dax, r.start, to_alloc);
+               rc = alloc_dev_dax_range(dev_dax, r.start, to_alloc, NULL);
        up_write(&dax_dev_rwsem);
        up_write(&dax_region_rwsem);
 
@@ -1506,7 +1600,7 @@ static struct dev_dax *__devm_create_dev_dax(struct 
dev_dax_data *data)
        device_initialize(dev);
        dev_set_name(dev, "dax%d.%d", dax_region->id, dev_dax->id);
 
-       rc = alloc_dev_dax_range(dev_dax, dax_region->res.start, data->size);
+       rc = alloc_dev_dax_range(dev_dax, dax_region->res.start, data->size, 
NULL);
        if (rc)
                goto err_range;
 
diff --git a/drivers/dax/bus.h b/drivers/dax/bus.h
index 6e739bfab932..7a115893a102 100644
--- a/drivers/dax/bus.h
+++ b/drivers/dax/bus.h
@@ -11,6 +11,7 @@ struct dev_dax;
 struct resource;
 struct dax_device;
 struct dax_region;
+struct dax_dc_ops;
 
 /* dax bus specific ioresource flags */
 #define IORESOURCE_DAX_STATIC BIT(0)
@@ -19,7 +20,7 @@ struct dax_region;
 
 struct dax_region *alloc_dax_region(struct device *parent, int region_id,
                struct range *range, int target_node, unsigned int align,
-               unsigned long flags);
+               unsigned long flags, struct dax_dc_ops *dc_ops);
 
 struct dev_dax_data {
        struct dax_region *dax_region;
diff --git a/drivers/dax/cxl.c b/drivers/dax/cxl.c
index f58fe992aa8d..690cf625e052 100644
--- a/drivers/dax/cxl.c
+++ b/drivers/dax/cxl.c
@@ -5,6 +5,84 @@
 
 #include "../cxl/cxl.h"
 #include "bus.h"
+#include "dax-private.h"
+
+static int __cxl_dax_add_resource(struct dax_region *dax_region,
+                                 struct dc_extent *dc_extent)
+{
+       struct device *dev = &dc_extent->dev;
+       resource_size_t start, length;
+
+       start = dax_region->res.start + dc_extent->hpa_range.start;
+       length = range_len(&dc_extent->hpa_range);
+       return dax_region_add_resource(dax_region, dev, start, length,
+                                      &dc_extent->group->uuid,
+                                      dc_extent->seq_num);
+}
+
+static int cxl_dax_add_resource(struct device *dev, void *data)
+{
+       struct dax_region *dax_region = data;
+       struct dc_extent *dc_extent;
+
+       dc_extent = to_dc_extent(dev);
+       if (!dc_extent)
+               return 0;
+
+       dev_dbg(dax_region->dev, "Adding resource HPA %pra (%pUb)\n",
+               &dc_extent->hpa_range, &dc_extent->group->uuid);
+
+       return __cxl_dax_add_resource(dax_region, dc_extent);
+}
+
+static int cxl_dax_group_add(struct dax_region *dax_region,
+                            struct cxl_dc_tag_group *group)
+{
+       struct dc_extent *dc_extent;
+       unsigned long index;
+       int rc;
+
+       xa_for_each(&group->dc_extents, index, dc_extent) {
+               rc = __cxl_dax_add_resource(dax_region, dc_extent);
+               if (rc)
+                       return rc;
+       }
+       return 0;
+}
+
+/*
+ * RELEASE is still a stub here — the atomic dax_region_rm_resources API
+ * and its wire-up land in the next commit.  An incoming RELEASE returns
+ * success and the cxl side proceeds to rm_tag_group(), which device-
+ * unregisters each dc_extent; the devm action armed by
+ * dax_region_add_resource() then tears down each dax_resource.
+ */
+static int cxl_dax_region_notify(struct device *dev,
+                                struct cxl_notify_data *notify_data)
+{
+       struct cxl_dax_region *cxlr_dax = to_cxl_dax_region(dev);
+       struct dax_region *dax_region = dev_get_drvdata(dev);
+       struct cxl_dc_tag_group *group = notify_data->group;
+
+       switch (notify_data->event) {
+       case DCD_ADD_CAPACITY:
+               return cxl_dax_group_add(dax_region, group);
+       case DCD_RELEASE_CAPACITY:
+               dev_dbg(&cxlr_dax->dev,
+                       "DCD RELEASE notify (tag %pUb): no-op (stub)\n",
+                       &group->uuid);
+               return 0;
+       case DCD_FORCED_CAPACITY_RELEASE:
+       default:
+               dev_err(&cxlr_dax->dev, "Unknown DC event %d\n",
+                       notify_data->event);
+               return -ENXIO;
+       }
+}
+
+static struct dax_dc_ops dc_ops = {
+       .is_extent = is_dc_extent,
+};
 
 static int cxl_dax_region_probe(struct device *dev)
 {
@@ -25,15 +103,18 @@ static int cxl_dax_region_probe(struct device *dev)
                flags = IORESOURCE_DAX_KMEM;
 
        dax_region = alloc_dax_region(dev, cxlr->id, &cxlr_dax->hpa_range, nid,
-                                     PMD_SIZE, flags);
+                                     PMD_SIZE, flags, &dc_ops);
        if (!dax_region)
                return -ENOMEM;
 
-       if (cxlr->mode == CXL_PARTMODE_DYNAMIC_RAM_A)
+       if (cxlr->mode == CXL_PARTMODE_DYNAMIC_RAM_A) {
+               device_for_each_child(&cxlr_dax->dev, dax_region,
+                                     cxl_dax_add_resource);
                /* Add empty seed dax device */
                dev_size = 0;
-       else
+       } else {
                dev_size = range_len(&cxlr_dax->hpa_range);
+       }
 
        data = (struct dev_dax_data) {
                .dax_region = dax_region,
@@ -48,6 +129,7 @@ static int cxl_dax_region_probe(struct device *dev)
 static struct cxl_driver cxl_dax_region_driver = {
        .name = "cxl_dax_region",
        .probe = cxl_dax_region_probe,
+       .notify = cxl_dax_region_notify,
        .id = CXL_DEVICE_DAX_REGION,
        .drv = {
                .suppress_bind_attrs = true,
diff --git a/drivers/dax/dax-private.h b/drivers/dax/dax-private.h
index ee8f3af8387f..f2ae5918f94d 100644
--- a/drivers/dax/dax-private.h
+++ b/drivers/dax/dax-private.h
@@ -8,6 +8,7 @@
 #include <linux/device.h>
 #include <linux/cdev.h>
 #include <linux/idr.h>
+#include <linux/uuid.h>
 
 /* private routines between core files */
 struct dax_device;
@@ -16,6 +17,14 @@ struct inode *dax_inode(struct dax_device *dax_dev);
 int dax_bus_init(void);
 void dax_bus_exit(void);
 
+/**
+ * struct dax_dc_ops - Operations for dc-backed regions
+ * @is_extent: return if the device is an extent
+ */
+struct dax_dc_ops {
+       bool (*is_extent)(struct device *dev);
+};
+
 /**
  * struct dax_region - mapping infrastructure for dax devices
  * @id: kernel-wide unique region for a memory range
@@ -27,6 +36,7 @@ void dax_bus_exit(void);
  * @res: resource tree to track instance allocations
  * @seed: allow userspace to find the first unbound seed device
  * @youngest: allow userspace to find the most recently created device
+ * @dc_ops: operations required for DC-backed regions
  */
 struct dax_region {
        int id;
@@ -38,6 +48,7 @@ struct dax_region {
        struct resource res;
        struct device *seed;
        struct device *youngest;
+       struct dax_dc_ops *dc_ops;
 };
 
 /**
@@ -57,11 +68,13 @@ struct dax_mapping {
  * @pgoff: page offset
  * @range: resource-span
  * @mapping: reference to the dax_mapping for this range
+ * @dax_resource: if not NULL; dax DC resource containing this range
  */
 struct dev_dax_range {
        unsigned long pgoff;
        struct range range;
        struct dax_mapping *mapping;
+       struct dax_resource *dax_resource;
 };
 
 /**
@@ -105,6 +118,42 @@ struct dev_dax {
  */
 void run_dax(struct dax_device *dax_dev);
 
+/**
+ * struct dax_resource - For DC DAX regions; an active resource
+ * @region: dax_region this resources is in
+ * @res: resource
+ * @uuid: tag identifying the backing extent; zero uuid means untagged
+ * @seq_num: 1..n assembly-order index within the tag group; 0 for the
+ *          untagged pool (uuid == 0).  For extents from a sharable
+ *          CXL DC partition this is the device-stamped shared_extn_seq
+ *          (CXL 3.1 Table 8-51).  For extents from a non-sharable
+ *          partition the cxl layer fills it in event arrival order, so
+ *          the dax layer can rely on a single 1..n dense invariant when
+ *          it claims a tagged group in uuid_store().
+ * @use_cnt: count the number of uses of this resource
+ *
+ * Changes to the dax_region and the dax_resources within it are protected by
+ * dax_region_rwsem
+ *
+ * dax_resource's are not intended to be used outside the dax layer.
+ */
+struct dax_resource {
+       struct dax_region *region;
+       struct resource *res;
+       uuid_t uuid;
+       u16 seq_num;
+       unsigned int use_cnt;
+};
+
+/*
+ * Similar to run_dax() dax_region_add_resource() is exported but is not
+ * intended to be a generic operation outside the dax subsystem.  It is only
+ * generic between the dax layer and the dax drivers.
+ */
+int dax_region_add_resource(struct dax_region *dax_region, struct device *dev,
+                           resource_size_t start, resource_size_t length,
+                           const uuid_t *tag, u16 seq_num);
+
 static inline struct dev_dax *to_dev_dax(struct device *dev)
 {
        return container_of(dev, struct dev_dax, dev);
diff --git a/drivers/dax/hmem/hmem.c b/drivers/dax/hmem/hmem.c
index af21f66bf872..be938c2a73f8 100644
--- a/drivers/dax/hmem/hmem.c
+++ b/drivers/dax/hmem/hmem.c
@@ -28,7 +28,7 @@ static int dax_hmem_probe(struct platform_device *pdev)
 
        mri = dev->platform_data;
        dax_region = alloc_dax_region(dev, pdev->id, &mri->range,
-                                     mri->target_node, PMD_SIZE, flags);
+                                     mri->target_node, PMD_SIZE, flags, NULL);
        if (!dax_region)
                return -ENOMEM;
 
diff --git a/drivers/dax/pmem.c b/drivers/dax/pmem.c
index bee93066a849..5b5be86768f3 100644
--- a/drivers/dax/pmem.c
+++ b/drivers/dax/pmem.c
@@ -53,7 +53,7 @@ static struct dev_dax *__dax_pmem_probe(struct device *dev)
        range.start += offset;
        dax_region = alloc_dax_region(dev, region_id, &range,
                        nd_region->target_node, le32_to_cpu(pfn_sb->align),
-                       IORESOURCE_DAX_STATIC);
+                       IORESOURCE_DAX_STATIC, NULL);
        if (!dax_region)
                return ERR_PTR(-ENOMEM);
 
-- 
2.43.0


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