dax: introduce dax_operations
Track a set of dax_operations per dax_device that can be set at
alloc_dax() time. These operations will be used to stop the abuse of
block_device_operations for communicating dax capabilities to
filesystems. It will also be used to replace the "pmem api" and move
pmem-specific cache maintenance, and other dax-driver-specific
filesystem-dax operations, to dax device methods. In particular this
allows us to stop abusing __copy_user_nocache(), via memcpy_to_pmem(),
with a driver specific replacement.
This is a standalone introduction of the operations. Follow on patches
convert each dax-driver and teach fs/dax.c to use ->direct_access() from
dax_operations instead of block_device_operations.
Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
diff --git a/drivers/dax/dax.h b/drivers/dax/dax.h
index 246a24d..617bbc2 100644
--- a/drivers/dax/dax.h
+++ b/drivers/dax/dax.h
@@ -13,7 +13,9 @@
#ifndef __DAX_H__
#define __DAX_H__
struct dax_device;
-struct dax_device *alloc_dax(void *private, const char *host);
+struct dax_operations;
+struct dax_device *alloc_dax(void *private, const char *host,
+ const struct dax_operations *ops);
void put_dax(struct dax_device *dax_dev);
bool dax_alive(struct dax_device *dax_dev);
void kill_dax(struct dax_device *dax_dev);
diff --git a/drivers/dax/device.c b/drivers/dax/device.c
index db68f4f..a0db055 100644
--- a/drivers/dax/device.c
+++ b/drivers/dax/device.c
@@ -645,7 +645,11 @@
goto err_id;
}
- dax_dev = alloc_dax(dev_dax, NULL);
+ /*
+ * No 'host' or dax_operations since there is no access to this
+ * device outside of mmap of the resulting character device.
+ */
+ dax_dev = alloc_dax(dev_dax, NULL, NULL);
if (!dax_dev)
goto err_dax;
diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index 8d44667..1a58542 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -17,6 +17,7 @@
#include <linux/cdev.h>
#include <linux/hash.h>
#include <linux/slab.h>
+#include <linux/dax.h>
#include <linux/fs.h>
static int nr_dax = CONFIG_NR_DEV_DAX;
@@ -61,6 +62,7 @@
const char *host;
void *private;
bool alive;
+ const struct dax_operations *ops;
};
bool dax_alive(struct dax_device *dax_dev)
@@ -208,7 +210,8 @@
spin_unlock(&dax_host_lock);
}
-struct dax_device *alloc_dax(void *private, const char *__host)
+struct dax_device *alloc_dax(void *private, const char *__host,
+ const struct dax_operations *ops)
{
struct dax_device *dax_dev;
const char *host;
@@ -229,6 +232,7 @@
goto err_dev;
dax_add_host(dax_dev, host);
+ dax_dev->ops = ops;
dax_dev->private = private;
return dax_dev;
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 9b2d5ba..74ebb92 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -7,6 +7,16 @@
#include <asm/pgtable.h>
struct iomap_ops;
+struct dax_device;
+struct dax_operations {
+ /*
+ * direct_access: translate a device-relative
+ * logical-page-offset into an absolute physical pfn. Return the
+ * number of pages available for DAX at that pfn.
+ */
+ long (*direct_access)(struct dax_device *, pgoff_t, long,
+ void **, pfn_t *);
+};
int dax_read_lock(void);
void dax_read_unlock(int id);