v4.19.13 snapshot.
diff --git a/include/linux/dax.h b/include/linux/dax.h
new file mode 100644
index 0000000..450b28d
--- /dev/null
+++ b/include/linux/dax.h
@@ -0,0 +1,177 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_DAX_H
+#define _LINUX_DAX_H
+
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/radix-tree.h>
+#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 *);
+ /* copy_from_iter: required operation for fs-dax direct-i/o */
+ size_t (*copy_from_iter)(struct dax_device *, pgoff_t, void *, size_t,
+ struct iov_iter *);
+ /* copy_to_iter: required operation for fs-dax direct-i/o */
+ size_t (*copy_to_iter)(struct dax_device *, pgoff_t, void *, size_t,
+ struct iov_iter *);
+};
+
+extern struct attribute_group dax_attribute_group;
+
+#if IS_ENABLED(CONFIG_DAX)
+struct dax_device *dax_get_by_host(const char *host);
+struct dax_device *alloc_dax(void *private, const char *host,
+ const struct dax_operations *ops);
+void put_dax(struct dax_device *dax_dev);
+void kill_dax(struct dax_device *dax_dev);
+void dax_write_cache(struct dax_device *dax_dev, bool wc);
+bool dax_write_cache_enabled(struct dax_device *dax_dev);
+#else
+static inline struct dax_device *dax_get_by_host(const char *host)
+{
+ return NULL;
+}
+static inline struct dax_device *alloc_dax(void *private, const char *host,
+ const struct dax_operations *ops)
+{
+ /*
+ * Callers should check IS_ENABLED(CONFIG_DAX) to know if this
+ * NULL is an error or expected.
+ */
+ return NULL;
+}
+static inline void put_dax(struct dax_device *dax_dev)
+{
+}
+static inline void kill_dax(struct dax_device *dax_dev)
+{
+}
+static inline void dax_write_cache(struct dax_device *dax_dev, bool wc)
+{
+}
+static inline bool dax_write_cache_enabled(struct dax_device *dax_dev)
+{
+ return false;
+}
+#endif
+
+struct writeback_control;
+int bdev_dax_pgoff(struct block_device *, sector_t, size_t, pgoff_t *pgoff);
+#if IS_ENABLED(CONFIG_FS_DAX)
+bool __bdev_dax_supported(struct block_device *bdev, int blocksize);
+static inline bool bdev_dax_supported(struct block_device *bdev, int blocksize)
+{
+ return __bdev_dax_supported(bdev, blocksize);
+}
+
+static inline struct dax_device *fs_dax_get_by_host(const char *host)
+{
+ return dax_get_by_host(host);
+}
+
+static inline void fs_put_dax(struct dax_device *dax_dev)
+{
+ put_dax(dax_dev);
+}
+
+struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev);
+int dax_writeback_mapping_range(struct address_space *mapping,
+ struct block_device *bdev, struct writeback_control *wbc);
+
+struct page *dax_layout_busy_page(struct address_space *mapping);
+bool dax_lock_mapping_entry(struct page *page);
+void dax_unlock_mapping_entry(struct page *page);
+#else
+static inline bool bdev_dax_supported(struct block_device *bdev,
+ int blocksize)
+{
+ return false;
+}
+
+static inline struct dax_device *fs_dax_get_by_host(const char *host)
+{
+ return NULL;
+}
+
+static inline void fs_put_dax(struct dax_device *dax_dev)
+{
+}
+
+static inline struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev)
+{
+ return NULL;
+}
+
+static inline struct page *dax_layout_busy_page(struct address_space *mapping)
+{
+ return NULL;
+}
+
+static inline int dax_writeback_mapping_range(struct address_space *mapping,
+ struct block_device *bdev, struct writeback_control *wbc)
+{
+ return -EOPNOTSUPP;
+}
+
+static inline bool dax_lock_mapping_entry(struct page *page)
+{
+ if (IS_DAX(page->mapping->host))
+ return true;
+ return false;
+}
+
+static inline void dax_unlock_mapping_entry(struct page *page)
+{
+}
+#endif
+
+int dax_read_lock(void);
+void dax_read_unlock(int id);
+bool dax_alive(struct dax_device *dax_dev);
+void *dax_get_private(struct dax_device *dax_dev);
+long dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff, long nr_pages,
+ void **kaddr, pfn_t *pfn);
+size_t dax_copy_from_iter(struct dax_device *dax_dev, pgoff_t pgoff, void *addr,
+ size_t bytes, struct iov_iter *i);
+size_t dax_copy_to_iter(struct dax_device *dax_dev, pgoff_t pgoff, void *addr,
+ size_t bytes, struct iov_iter *i);
+void dax_flush(struct dax_device *dax_dev, void *addr, size_t size);
+
+ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
+ const struct iomap_ops *ops);
+vm_fault_t dax_iomap_fault(struct vm_fault *vmf, enum page_entry_size pe_size,
+ pfn_t *pfnp, int *errp, const struct iomap_ops *ops);
+vm_fault_t dax_finish_sync_fault(struct vm_fault *vmf,
+ enum page_entry_size pe_size, pfn_t pfn);
+int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index);
+int dax_invalidate_mapping_entry_sync(struct address_space *mapping,
+ pgoff_t index);
+
+#ifdef CONFIG_FS_DAX
+int __dax_zero_page_range(struct block_device *bdev,
+ struct dax_device *dax_dev, sector_t sector,
+ unsigned int offset, unsigned int length);
+#else
+static inline int __dax_zero_page_range(struct block_device *bdev,
+ struct dax_device *dax_dev, sector_t sector,
+ unsigned int offset, unsigned int length)
+{
+ return -ENXIO;
+}
+#endif
+
+static inline bool dax_mapping(struct address_space *mapping)
+{
+ return mapping->host && IS_DAX(mapping->host);
+}
+
+#endif