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Subject[PATCH 7/8] dax: add / remove dax devices after provisioning
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Date
Create a new device-dax seed when incrementing the size of the existing
seed from zero.

Destroy a device-dax instance when its size changes from non-zero to
zero.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
drivers/dax/dax.c | 195 +++++++++++++++++++++++++++++++++++------------------
1 file changed, 128 insertions(+), 67 deletions(-)

diff --git a/drivers/dax/dax.c b/drivers/dax/dax.c
index 9b641c079e52..b130eff91b83 100644
--- a/drivers/dax/dax.c
+++ b/drivers/dax/dax.c
@@ -15,6 +15,7 @@
#include <linux/device.h>
#include <linux/mount.h>
#include <linux/pfn_t.h>
+#include <linux/async.h>
#include <linux/hash.h>
#include <linux/cdev.h>
#include <linux/slab.h>
@@ -32,6 +33,7 @@ static struct vfsmount *dax_mnt;
static struct kmem_cache *dax_cache __read_mostly;
static struct super_block *dax_superblock __read_mostly;
MODULE_PARM_DESC(nr_dax, "max number of device-dax instances");
+static ASYNC_DOMAIN_EXCLUSIVE(dax_dev_async);

/**
* struct dax_region - mapping infrastructure for dax devices
@@ -329,6 +331,7 @@ static void dax_region_free(struct kref *kref)
"%s: child count not zero\n",
dev_name(dax_region->dev));
kfree(dax_region);
+ module_put(THIS_MODULE);
}

void dax_region_put(struct dax_region *dax_region)
@@ -377,15 +380,22 @@ struct dax_region *alloc_dax_region(struct device *parent, int region_id,
dax_region->align = align;
dax_region->dev = parent;
dax_region->base = addr;
- if (sysfs_create_groups(&parent->kobj, dax_region_attribute_groups)) {
- kfree(dax_region);
- return NULL;;
- }
+ if (!try_module_get(THIS_MODULE))
+ goto err_module;
+
+ if (sysfs_create_groups(&parent->kobj, dax_region_attribute_groups))
+ goto err_groups;

kref_get(&dax_region->kref);
if (devm_add_action_or_reset(parent, dax_region_unregister, dax_region))
return NULL;
return dax_region;
+
+err_groups:
+ module_put(THIS_MODULE);
+err_module:
+ kfree(dax_region);
+ return NULL;
}
EXPORT_SYMBOL_GPL(alloc_dax_region);

@@ -402,6 +412,9 @@ static unsigned long long dax_dev_size(struct dax_dev *dax_dev)

WARN_ON_ONCE(!mutex_is_locked(&dax_region->lock));

+ if (!dax_dev->alive)
+ return 0;
+
for (i = 0; i < dax_dev->num_resources; i++)
size += resource_size(dax_dev->res[i]);

@@ -415,6 +428,9 @@ static ssize_t size_show(struct device *dev,
struct dax_dev *dax_dev = to_dax_dev(dev);
struct dax_region *dax_region = dax_dev->region;

+ /* flush previous size operations */
+ async_synchronize_full_domain(&dax_dev_async);
+
mutex_lock(&dax_region->lock);
size = dax_dev_size(dax_dev);
mutex_unlock(&dax_region->lock);
@@ -494,6 +510,89 @@ static int dax_dev_adjust_resource(struct dax_dev *dax_dev,
return rc;
}

+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 unregister_dax_dev(void *dev)
+{
+ struct dax_dev *dax_dev = to_dax_dev(dev);
+ struct dax_region *dax_region = dax_dev->region;
+ struct cdev *cdev = &dax_dev->cdev;
+ int i;
+
+ dev_dbg(dev, "%s\n", __func__);
+
+ /*
+ * Note, rcu is not protecting the liveness of dax_dev, rcu is
+ * ensuring that any fault handlers that might have seen
+ * dax_dev->alive == true, have completed. Any fault handlers
+ * that start after synchronize_rcu() has started will abort
+ * upon seeing dax_dev->alive == false.
+ */
+ dax_dev->alive = false;
+ synchronize_rcu();
+ 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]));
+ if (dax_region->seed == dev)
+ dax_region->seed = NULL;
+ mutex_unlock(&dax_region->lock);
+ atomic_dec(&dax_region->child_count);
+
+ cdev_del(cdev);
+ device_unregister(dev);
+}
+
+static void dax_dev_async_unregister(void *d, async_cookie_t cookie)
+{
+ struct device *dev = d;
+ struct dax_dev *dax_dev = to_dax_dev(dev);
+ struct dax_region *dax_region = dax_dev->region;
+
+ /*
+ * Check that we still have an enabled region, if not then this
+ * device was unregistered when the region was disabled.
+ */
+ device_lock(dax_region->dev);
+ if (dev_get_drvdata(dax_region->dev)) {
+ devm_remove_action(dax_region->dev, unregister_dax_dev, dev);
+ unregister_dax_dev(dev);
+ }
+ device_unlock(dax_region->dev);
+
+ put_device(dev);
+}
+
static int dax_dev_shrink(struct dax_region *dax_region,
struct dax_dev *dax_dev, unsigned long long size)
{
@@ -552,6 +651,14 @@ static int dax_dev_shrink(struct dax_region *dax_region,
*/
unmap_mapping_range(mapping, size, dev_size - size, 1);

+ if (size == 0 && &dax_dev->dev != dax_region->seed) {
+ get_device(&dax_dev->dev);
+ dax_dev->alive = false;
+ synchronize_rcu();
+ async_schedule_domain(dax_dev_async_unregister, &dax_dev->dev,
+ &dax_dev_async);
+ }
+
return rc;
}

@@ -607,6 +714,9 @@ static ssize_t dax_dev_resize(struct dax_region *dax_region,
resource_size_t region_end;
int i, rc;

+ if (!dax_dev->alive)
+ return -ENXIO;
+
if (size == dev_size)
return 0;
if (size > dev_size && size - dev_size > avail)
@@ -686,6 +796,20 @@ static ssize_t dax_dev_resize(struct dax_region *dax_region,
}
}

+ device_lock(dax_region->dev);
+ if (dev_get_drvdata(dax_region->dev) && dev_size == 0
+ && &dax_dev->dev == dax_region->seed) {
+ struct dax_dev *seed;
+
+ seed = devm_create_dax_dev(dax_region, NULL, 0);
+ if (IS_ERR(seed))
+ dev_warn(dax_region->dev,
+ "failed to create new region seed\n");
+ else
+ dax_region->seed = &seed->dev;
+ }
+ device_unlock(dax_region->dev);
+
return 0;
}

@@ -1001,35 +1125,6 @@ static const struct file_operations dax_fops = {
.mmap = dax_mmap,
};

-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);
@@ -1043,40 +1138,6 @@ static void dax_dev_release(struct device *dev)
kfree(dax_dev);
}

-static void unregister_dax_dev(void *dev)
-{
- struct dax_dev *dax_dev = to_dax_dev(dev);
- struct dax_region *dax_region = dax_dev->region;
- struct cdev *cdev = &dax_dev->cdev;
- int i;
-
- dev_dbg(dev, "%s\n", __func__);
-
- /*
- * Note, rcu is not protecting the liveness of dax_dev, rcu is
- * ensuring that any fault handlers that might have seen
- * dax_dev->alive == true, have completed. Any fault handlers
- * that start after synchronize_rcu() has started will abort
- * upon seeing dax_dev->alive == false.
- */
- dax_dev->alive = false;
- synchronize_rcu();
- 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]));
- if (dax_region->seed == dev)
- dax_region->seed = NULL;
- mutex_unlock(&dax_region->lock);
- atomic_dec(&dax_region->child_count);
-
- cdev_del(cdev);
- device_unregister(dev);
-}
-
struct dax_dev *devm_create_dax_dev(struct dax_region *dax_region,
struct resource *res, int count)
{
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