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Subject[PATCH 4/7] dax: embed a struct device in dax_dev
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The kref in dax_dev can be made redundant if the final put_device() on
the device associated with the dax_dev frees the dax_dev. This can be
accomplished by embedding a struct device in struct dax_dev, open coding
device_create() and specifying a custom release method.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
drivers/dax/dax.c | 130 ++++++++++++++++++-----------------------------------
1 file changed, 45 insertions(+), 85 deletions(-)

diff --git a/drivers/dax/dax.c b/drivers/dax/dax.c
index 994dfa507dfb..181d2a5a21e4 100644
--- a/drivers/dax/dax.c
+++ b/drivers/dax/dax.c
@@ -49,7 +49,6 @@ struct dax_region {
* struct dax_dev - subdivision of a dax region
* @region - parent region
* @dev - device backing the character device
- * @kref - enable this data to be tracked in filp->private_data
* @alive - !alive + rcu grace period == no new mappings can be established
* @id - child id in the region
* @num_resources - number of physical address extents in this device
@@ -57,8 +56,7 @@ struct dax_region {
*/
struct dax_dev {
struct dax_region *region;
- struct device *dev;
- struct kref kref;
+ struct device dev;
bool alive;
int id;
int num_resources;
@@ -79,20 +77,6 @@ void dax_region_put(struct dax_region *dax_region)
}
EXPORT_SYMBOL_GPL(dax_region_put);

-static void dax_dev_free(struct kref *kref)
-{
- struct dax_dev *dax_dev;
-
- dax_dev = container_of(kref, struct dax_dev, kref);
- dax_region_put(dax_dev->region);
- kfree(dax_dev);
-}
-
-static void dax_dev_put(struct dax_dev *dax_dev)
-{
- kref_put(&dax_dev->kref, dax_dev_free);
-}
-
struct dax_region *alloc_dax_region(struct device *parent, int region_id,
struct resource *res, unsigned int align, void *addr,
unsigned long pfn_flags)
@@ -117,10 +101,15 @@ struct dax_region *alloc_dax_region(struct device *parent, int region_id,
}
EXPORT_SYMBOL_GPL(alloc_dax_region);

+static struct dax_dev *to_dax_dev(struct device *dev)
+{
+ return container_of(dev, struct dax_dev, dev);
+}
+
static ssize_t size_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
- struct dax_dev *dax_dev = dev_get_drvdata(dev);
+ struct dax_dev *dax_dev = to_dax_dev(dev);
unsigned long long size = 0;
int i;

@@ -149,7 +138,7 @@ static int check_vma(struct dax_dev *dax_dev, struct vm_area_struct *vma,
const char *func)
{
struct dax_region *dax_region = dax_dev->region;
- struct device *dev = dax_dev->dev;
+ struct device *dev = &dax_dev->dev;
unsigned long mask;

if (!dax_dev->alive)
@@ -214,7 +203,7 @@ static int __dax_dev_fault(struct dax_dev *dax_dev, struct vm_area_struct *vma,
struct vm_fault *vmf)
{
unsigned long vaddr = (unsigned long) vmf->virtual_address;
- struct device *dev = dax_dev->dev;
+ struct device *dev = &dax_dev->dev;
struct dax_region *dax_region;
int rc = VM_FAULT_SIGBUS;
phys_addr_t phys;
@@ -254,7 +243,7 @@ static int dax_dev_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
struct file *filp = vma->vm_file;
struct dax_dev *dax_dev = filp->private_data;

- dev_dbg(dax_dev->dev, "%s: %s: %s (%#lx - %#lx)\n", __func__,
+ dev_dbg(&dax_dev->dev, "%s: %s: %s (%#lx - %#lx)\n", __func__,
current->comm, (vmf->flags & FAULT_FLAG_WRITE)
? "write" : "read", vma->vm_start, vma->vm_end);
rcu_read_lock();
@@ -269,7 +258,7 @@ static int __dax_dev_pmd_fault(struct dax_dev *dax_dev,
unsigned int flags)
{
unsigned long pmd_addr = addr & PMD_MASK;
- struct device *dev = dax_dev->dev;
+ struct device *dev = &dax_dev->dev;
struct dax_region *dax_region;
phys_addr_t phys;
pgoff_t pgoff;
@@ -311,7 +300,7 @@ static int dax_dev_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
struct file *filp = vma->vm_file;
struct dax_dev *dax_dev = filp->private_data;

- dev_dbg(dax_dev->dev, "%s: %s: %s (%#lx - %#lx)\n", __func__,
+ dev_dbg(&dax_dev->dev, "%s: %s: %s (%#lx - %#lx)\n", __func__,
current->comm, (flags & FAULT_FLAG_WRITE)
? "write" : "read", vma->vm_start, vma->vm_end);

@@ -322,29 +311,9 @@ static int dax_dev_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
return rc;
}

-static void dax_dev_vm_open(struct vm_area_struct *vma)
-{
- struct file *filp = vma->vm_file;
- struct dax_dev *dax_dev = filp->private_data;
-
- dev_dbg(dax_dev->dev, "%s\n", __func__);
- kref_get(&dax_dev->kref);
-}
-
-static void dax_dev_vm_close(struct vm_area_struct *vma)
-{
- struct file *filp = vma->vm_file;
- struct dax_dev *dax_dev = filp->private_data;
-
- dev_dbg(dax_dev->dev, "%s\n", __func__);
- dax_dev_put(dax_dev);
-}
-
static const struct vm_operations_struct dax_dev_vm_ops = {
.fault = dax_dev_fault,
.pmd_fault = dax_dev_pmd_fault,
- .open = dax_dev_vm_open,
- .close = dax_dev_vm_close,
};

static int dax_mmap(struct file *filp, struct vm_area_struct *vma)
@@ -352,13 +321,12 @@ static int dax_mmap(struct file *filp, struct vm_area_struct *vma)
struct dax_dev *dax_dev = filp->private_data;
int rc;

- dev_dbg(dax_dev->dev, "%s\n", __func__);
+ dev_dbg(&dax_dev->dev, "%s\n", __func__);

rc = check_vma(dax_dev, vma, __func__);
if (rc)
return rc;

- kref_get(&dax_dev->kref);
vma->vm_ops = &dax_dev_vm_ops;
vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE;
return 0;
@@ -420,30 +388,20 @@ static int dax_open(struct inode *inode, struct file *filp)
if (!dev)
return -ENXIO;

- device_lock(dev);
- dax_dev = dev_get_drvdata(dev);
- if (dax_dev) {
- dev_dbg(dev, "%s\n", __func__);
- filp->private_data = dax_dev;
- kref_get(&dax_dev->kref);
- inode->i_flags = S_DAX;
- }
- device_unlock(dev);
+ dax_dev = to_dax_dev(dev);
+ dev_dbg(dev, "%s\n", __func__);
+ filp->private_data = dax_dev;
+ inode->i_flags = S_DAX;

- if (!dax_dev) {
- put_device(dev);
- return -ENXIO;
- }
return 0;
}

static int dax_release(struct inode *inode, struct file *filp)
{
struct dax_dev *dax_dev = filp->private_data;
- struct device *dev = dax_dev->dev;
+ struct device *dev = &dax_dev->dev;

- dev_dbg(dax_dev->dev, "%s\n", __func__);
- dax_dev_put(dax_dev);
+ dev_dbg(dev, "%s\n", __func__);
put_device(dev);

return 0;
@@ -458,12 +416,21 @@ static const struct file_operations dax_fops = {
.mmap = dax_mmap,
};

-static void unregister_dax_dev(void *_dev)
+static void dax_dev_release(struct device *dev)
{
- struct device *dev = _dev;
- struct dax_dev *dax_dev = dev_get_drvdata(dev);
+ struct dax_dev *dax_dev = to_dax_dev(dev);
struct dax_region *dax_region = dax_dev->region;

+ ida_simple_remove(&dax_region->ida, dax_dev->id);
+ ida_simple_remove(&dax_minor_ida, MINOR(dev->devt));
+ dax_region_put(dax_region);
+ kfree(dax_dev);
+}
+
+static void unregister_dax_dev(void *dev)
+{
+ struct dax_dev *dax_dev = to_dax_dev(dev);
+
dev_dbg(dev, "%s\n", __func__);

/*
@@ -475,13 +442,7 @@ static void unregister_dax_dev(void *_dev)
*/
dax_dev->alive = false;
synchronize_rcu();
-
- get_device(dev);
device_unregister(dev);
- ida_simple_remove(&dax_region->ida, dax_dev->id);
- ida_simple_remove(&dax_minor_ida, MINOR(dev->devt));
- put_device(dev);
- dax_dev_put(dax_dev);
}

int devm_create_dax_dev(struct dax_region *dax_region, struct resource *res,
@@ -498,7 +459,6 @@ int devm_create_dax_dev(struct dax_region *dax_region, struct resource *res,
return -ENOMEM;
memcpy(dax_dev->res, res, sizeof(*res) * count);
dax_dev->num_resources = count;
- kref_init(&dax_dev->kref);
dax_dev->alive = true;
dax_dev->region = dax_region;
kref_get(&dax_region->kref);
@@ -516,27 +476,27 @@ int devm_create_dax_dev(struct dax_region *dax_region, struct resource *res,
}

dev_t = MKDEV(dax_major, minor);
- dev = device_create_with_groups(dax_class, parent, dev_t, dax_dev,
- dax_attribute_groups, "dax%d.%d", dax_region->id,
- dax_dev->id);
- if (IS_ERR(dev)) {
- rc = PTR_ERR(dev);
- goto err_create;
- }
- dax_dev->dev = dev;

- rc = devm_add_action_or_reset(dax_region->dev, unregister_dax_dev, dev);
- if (rc)
+ dev = &dax_dev->dev;
+ device_initialize(dev);
+ dev->devt = dev_t;
+ dev->class = dax_class;
+ dev->parent = parent;
+ dev->groups = dax_attribute_groups;
+ dev->release = dax_dev_release;
+ dev_set_name(dev, "dax%d.%d", dax_region->id, dax_dev->id);
+ rc = device_add(dev);
+ if (rc) {
+ put_device(dev);
return rc;
+ }

- return 0;
+ return devm_add_action_or_reset(dax_region->dev, unregister_dax_dev, dev);

- err_create:
- ida_simple_remove(&dax_minor_ida, minor);
err_minor:
ida_simple_remove(&dax_region->ida, dax_dev->id);
err_id:
- dax_dev_put(dax_dev);
+ kfree(dax_dev);

return rc;
}
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