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Subject[PATCH 4/8] dax: use multi-order radix for resource lookup
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Before we add support for multiple discontiguous extents in a device-dax
region, convert the file-offset to physical-address lookup to use the
multi-order radix tree.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
drivers/dax/Kconfig | 1
drivers/dax/dax.c | 120 ++++++++++++++++++++++++++++++++++++++++++++-------
2 files changed, 104 insertions(+), 17 deletions(-)

diff --git a/drivers/dax/Kconfig b/drivers/dax/Kconfig
index 3e2ab3b14eea..f01d1b353b8e 100644
--- a/drivers/dax/Kconfig
+++ b/drivers/dax/Kconfig
@@ -2,6 +2,7 @@ menuconfig DEV_DAX
tristate "DAX: direct access to differentiated memory"
default m if NVDIMM_DAX
depends on TRANSPARENT_HUGEPAGE
+ select RADIX_TREE_MULTIORDER
help
Support raw access to differentiated (persistence, bandwidth,
latency...) memory via an mmap(2) capable character
diff --git a/drivers/dax/dax.c b/drivers/dax/dax.c
index c9ba011e333b..d878a56cf3e3 100644
--- a/drivers/dax/dax.c
+++ b/drivers/dax/dax.c
@@ -458,28 +458,34 @@ static int check_vma(struct dax_dev *dax_dev, struct vm_area_struct *vma,
return 0;
}

+/*
+ * Reuse the unused ->desc attribute of a dax_dev resource to store the
+ * relative pgoff of the resource within the device.
+ */
+static unsigned long to_dev_pgoff(struct resource *res)
+{
+ return res->desc;
+}
+
+static void set_dev_pgoff(struct resource *res, unsigned long dev_pgoff)
+{
+ res->desc = dev_pgoff;
+}
+
static phys_addr_t pgoff_to_phys(struct dax_dev *dax_dev, pgoff_t pgoff,
unsigned long size)
{
+ struct address_space *mapping = dax_dev->inode->i_mapping;
+ phys_addr_t res_offset;
struct resource *res;
- phys_addr_t phys;
- int i;
-
- for (i = 0; i < dax_dev->num_resources; i++) {
- res = dax_dev->res[i];
- phys = pgoff * PAGE_SIZE + res->start;
- if (phys >= res->start && phys <= res->end)
- break;
- pgoff -= PHYS_PFN(resource_size(res));
- }
-
- if (i < dax_dev->num_resources) {
- res = dax_dev->res[i];
- if (phys + size - 1 <= res->end)
- return phys;
- }

- return -1;
+ res = radix_tree_lookup(&mapping->page_tree, pgoff);
+ if (!res)
+ return -1;
+ res_offset = PFN_PHYS(pgoff - to_dev_pgoff(res));
+ if (res_offset + size >= resource_size(res))
+ return -1;
+ return res->start + res_offset;
}

static int __dax_dev_fault(struct dax_dev *dax_dev, struct vm_area_struct *vma,
@@ -682,6 +688,58 @@ static const struct file_operations dax_fops = {
.mmap = dax_mmap,
};

+static unsigned order_at(struct resource *res, unsigned long pgoff)
+{
+ unsigned long dev_pgoff = to_dev_pgoff(res) + pgoff;
+ unsigned long nr_pages = PHYS_PFN(resource_size(res));
+ unsigned order_max, order_pgoff;
+
+ if (nr_pages == pgoff)
+ return UINT_MAX;
+
+ /*
+ * What is the largest power-of-2 range available from this
+ * resource pgoff to the end of the resource range, considering
+ * the alignment of the current dev_pgoff?
+ */
+ order_pgoff = ilog2(nr_pages | dev_pgoff);
+ order_max = ilog2(nr_pages - pgoff);
+ return min(order_max, order_pgoff);
+}
+
+#define foreach_order_pgoff(res, order, pgoff) \
+ for (pgoff = 0, order = order_at((res), pgoff); order < UINT_MAX; \
+ pgoff += 1UL << order, order = order_at(res, pgoff))
+
+static void clear_dax_dev_radix(struct dax_dev *dax_dev)
+{
+ struct address_space *mapping = dax_dev->inode->i_mapping;
+ struct radix_tree_iter iter;
+ void **slot;
+
+ rcu_read_lock();
+ radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, 0) {
+ struct resource *res;
+ unsigned long pgoff;
+ unsigned order;
+
+ res = radix_tree_deref_slot(slot);
+ if (unlikely(!res))
+ continue;
+ if (radix_tree_deref_retry(res)) {
+ slot = radix_tree_iter_retry(&iter);
+ continue;
+ }
+
+ foreach_order_pgoff(res, order, pgoff)
+ radix_tree_delete(&mapping->page_tree,
+ to_dev_pgoff(res) + pgoff);
+ }
+ rcu_read_unlock();
+
+ synchronize_rcu();
+}
+
static void dax_dev_release(struct device *dev)
{
struct dax_dev *dax_dev = to_dax_dev(dev);
@@ -716,6 +774,7 @@ static void unregister_dax_dev(void *dev)
unmap_mapping_range(dax_dev->inode->i_mapping, 0, 0, 1);

mutex_lock(&dax_region->lock);
+ clear_dax_dev_radix(dax_dev);
for (i = 0; i < dax_dev->num_resources; i++)
__release_region(&dax_region->res, dax_dev->res[i]->start,
resource_size(dax_dev->res[i]));
@@ -734,6 +793,7 @@ struct dax_dev *devm_create_dax_dev(struct dax_region *dax_region,
struct device *parent = dax_region->dev;
struct dax_dev *dax_dev;
int rc = 0, minor, i;
+ unsigned long pgoff;
struct device *dev;
struct cdev *cdev;
dev_t dev_t;
@@ -790,6 +850,28 @@ struct dax_dev *devm_create_dax_dev(struct dax_region *dax_region,
goto err_inode;
}

+ for (i = 0, pgoff = 0; i < count; i++) {
+ struct address_space *mapping = dax_dev->inode->i_mapping;
+ struct resource *dax_res;
+ int order;
+
+ dax_res = dax_dev->res[i];
+ set_dev_pgoff(dax_res, pgoff);
+ mutex_lock(&dax_region->lock);
+ foreach_order_pgoff(dax_res, order, pgoff) {
+ rc = __radix_tree_insert(&mapping->page_tree,
+ to_dev_pgoff(dax_res) + pgoff, order,
+ dax_res);
+ if (rc)
+ break;
+ }
+ mutex_unlock(&dax_region->lock);
+ pgoff = to_dev_pgoff(dax_res) + PHYS_PFN(resource_size(dax_res));
+
+ if (rc)
+ goto err_radix_insert;
+ }
+
/* device_initialize() so cdev can reference kobj parent */
device_initialize(dev);

@@ -840,6 +922,10 @@ struct dax_dev *devm_create_dax_dev(struct dax_region *dax_region,
return dax_dev;

err_cdev:
+ mutex_lock(&dax_region->lock);
+ clear_dax_dev_radix(dax_dev);
+ mutex_unlock(&dax_region->lock);
+ err_radix_insert:
iput(dax_dev->inode);
err_inode:
ida_simple_remove(&dax_minor_ida, minor);
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