[PATCH v8 7/9] dax: add dax holder helper for filesystems

[Shiyang Ruan]

Add these helper functions, and export them for filesystem use.

Signed-off-by: Shiyang Ruan <ruansy.f...@fujitsu.com>
---
 drivers/dax/super.c | 19 +++++++++++++++++++
 include/linux/dax.h | 15 +++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index a19fcc0a54f3..acbe7078ce4c 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -114,6 +114,25 @@ struct dax_device *fs_dax_get_by_bdev(struct block_device 
*bdev, u64 *start_off)
        return dax_dev;
 }
 EXPORT_SYMBOL_GPL(fs_dax_get_by_bdev);
+
+void fs_dax_register_holder(struct dax_device *dax_dev, void *holder,
+               const struct dax_holder_operations *ops)
+{
+       dax_set_holder(dax_dev, holder, ops);
+}
+EXPORT_SYMBOL_GPL(fs_dax_register_holder);
+
+void fs_dax_unregister_holder(struct dax_device *dax_dev)
+{
+       dax_set_holder(dax_dev, NULL, NULL);
+}
+EXPORT_SYMBOL_GPL(fs_dax_unregister_holder);
+
+void *fs_dax_get_holder(struct dax_device *dax_dev)
+{
+       return dax_get_holder(dax_dev);
+}
+EXPORT_SYMBOL_GPL(fs_dax_get_holder);
 #endif /* CONFIG_BLOCK && CONFIG_FS_DAX */
 
 enum dax_device_flags {
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 500d048d444e..15a0ad4c248d 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -140,6 +140,10 @@ static inline void fs_put_dax(struct dax_device *dax_dev)
 {
        put_dax(dax_dev);
 }
+void fs_dax_register_holder(struct dax_device *dax_dev, void *holder,
+               const struct dax_holder_operations *ops);
+void fs_dax_unregister_holder(struct dax_device *dax_dev);
+void *fs_dax_get_holder(struct dax_device *dax_dev);
 #else
 static inline int dax_add_host(struct dax_device *dax_dev, struct gendisk 
*disk)
 {
@@ -156,6 +160,17 @@ static inline struct dax_device *fs_dax_get_by_bdev(struct 
block_device *bdev,
 static inline void fs_put_dax(struct dax_device *dax_dev)
 {
 }
+static inline void fs_dax_register_holder(struct dax_device *dax_dev,
+               void *holder, const struct dax_holder_operations *ops)
+{
+}
+static inline void fs_dax_unregister_holder(struct dax_device *dax_dev)
+{
+}
+static inline void *fs_dax_get_holder(struct dax_device *dax_dev)
+{
+       return NULL;
+}
 #endif /* CONFIG_BLOCK && CONFIG_FS_DAX */
 
 #if IS_ENABLED(CONFIG_FS_DAX)
-- 
2.34.0