diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index a0d296b0d826..d91ff283a966 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3693,6 +3693,7 @@ int btree_readahead_hook(struct extent_buffer *eb, int err);
 #ifdef CONFIG_FS_DAX
 /* dax.c */
 ssize_t btrfs_file_dax_read(struct kiocb *iocb, struct iov_iter *to);
+ssize_t btrfs_file_dax_write(struct kiocb *iocb, struct iov_iter *from);
 #endif /* CONFIG_FS_DAX */
 
 static inline int is_fstree(u64 rootid)
diff --git a/fs/btrfs/dax.c b/fs/btrfs/dax.c
index 5a297674adec..4000259a426c 100644
--- a/fs/btrfs/dax.c
+++ b/fs/btrfs/dax.c
@@ -2,6 +2,7 @@
 #include <linux/uio.h>
 #include "ctree.h"
 #include "btrfs_inode.h"
+#include "extent_io.h"
 
 static ssize_t em_dax_rw(struct inode *inode, struct extent_map *em, u64 pos,
 		u64 len, struct iov_iter *iter)
@@ -71,3 +72,123 @@ ssize_t btrfs_file_dax_read(struct kiocb *iocb, struct iov_iter *to)
         return done ? done : ret;
 }
 
+static int copy_extent_page(struct extent_map *em, void *daddr, u64 pos)
+{
+        struct dax_device *dax_dev;
+	void *saddr;
+	sector_t start;
+	size_t len;
+
+	if (em->block_start == EXTENT_MAP_HOLE) {
+		memset(daddr, 0, PAGE_SIZE);
+	} else {
+		dax_dev = fs_dax_get_by_bdev(em->bdev);
+		start = (get_start_sect(em->bdev) << 9) + (em->block_start + (pos - em->start));
+		len = dax_direct_access(dax_dev, PHYS_PFN(start), 1, &saddr, NULL);
+		memcpy(daddr, saddr, PAGE_SIZE);
+	}
+	free_extent_map(em);
+
+	return 0;
+}
+
+
+ssize_t btrfs_file_dax_write(struct kiocb *iocb, struct iov_iter *from)
+{
+	ssize_t ret, done = 0, count = iov_iter_count(from);
+        struct inode *inode = file_inode(iocb->ki_filp);
+	u64 pos = iocb->ki_pos;
+	u64 start = round_down(pos, PAGE_SIZE);
+	u64 end = round_up(pos + count, PAGE_SIZE);
+	struct extent_state *cached_state = NULL;
+	struct extent_changeset *data_reserved = NULL;
+	struct extent_map *first = NULL, *last = NULL;
+
+	ret = btrfs_delalloc_reserve_space(inode, &data_reserved, start, end - start);
+	if (ret < 0)
+		return ret;
+
+	/* Grab a reference of the first extent to copy data */
+	if (start < pos) {
+		first = btrfs_get_extent(BTRFS_I(inode), NULL, 0, start, end - start, 0);
+		if (IS_ERR(first)) {
+			ret = PTR_ERR(first);
+			goto out2;
+		}
+	}
+
+	/* Grab a reference of the last extent to copy data */
+	if (pos + count < end) {
+		last = btrfs_get_extent(BTRFS_I(inode), NULL, 0, end - PAGE_SIZE, PAGE_SIZE, 0);
+		if (IS_ERR(last)) {
+			ret = PTR_ERR(last);
+			goto out2;
+		}
+	}
+
+	lock_extent_bits(&BTRFS_I(inode)->io_tree, start, end, &cached_state);
+	while (done < count) {
+		struct extent_map *em;
+		struct dax_device *dax_dev;
+		int offset = pos & (PAGE_SIZE - 1);
+		u64 estart = round_down(pos, PAGE_SIZE);
+		u64 elen = end - estart;
+		size_t len = count - done;
+		sector_t dstart;
+		void *daddr;
+		ssize_t maplen;
+
+		/* Read the current extent */
+                em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, estart, elen, 0);
+		if (IS_ERR(em)) {
+			ret = PTR_ERR(em);
+			goto out;
+		}
+
+		/* Get a new extent */
+		ret = btrfs_get_extent_map_write(&em, NULL, inode, estart, elen);
+		if (ret < 0)
+			goto out;
+
+		dax_dev = fs_dax_get_by_bdev(em->bdev);
+		/* Calculate start address start of destination extent */
+		dstart = (get_start_sect(em->bdev) << 9) + em->block_start;
+		maplen = dax_direct_access(dax_dev, PHYS_PFN(dstart),
+				PHYS_PFN(em->len), &daddr, NULL);
+
+		/* Copy front of extent page */
+		if (offset)
+			ret = copy_extent_page(first, daddr, estart);
+
+		/* Copy end of extent page */
+		if ((pos + len > estart + PAGE_SIZE) && (pos + len < em->start + em->len))
+			ret = copy_extent_page(last, daddr + em->len - PAGE_SIZE, em->start + em->len - PAGE_SIZE);
+
+		/* Copy the data from the iter */
+		maplen = PFN_PHYS(maplen);
+		maplen -= offset;
+		ret = dax_copy_from_iter(dax_dev, dstart, daddr + offset, maplen, from);
+		if (ret < 0)
+			goto out;
+		pos += ret;
+		done += ret;
+	}
+out:
+	unlock_extent_cached(&BTRFS_I(inode)->io_tree, start, end, &cached_state);
+	if (done) {
+		btrfs_update_ordered_extent(inode, start,
+				end - start, true);
+		iocb->ki_pos += done;
+		if (iocb->ki_pos > i_size_read(inode))
+			i_size_write(inode, iocb->ki_pos);
+	}
+
+	btrfs_delalloc_release_extents(BTRFS_I(inode), count, false);
+out2:
+	if (count - done > 0)
+		btrfs_delalloc_release_space(inode, data_reserved, pos,
+				count - done, true);
+	extent_changeset_free(data_reserved);
+        return done ? done : ret;
+
+}
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index ef6ed93f44d1..29a3b12e6660 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1964,7 +1964,9 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
 	if (sync)
 		atomic_inc(&BTRFS_I(inode)->sync_writers);
 
-	if (iocb->ki_flags & IOCB_DIRECT) {
+	if (IS_DAX(inode)) {
+		num_written = btrfs_file_dax_write(iocb, from);
+	} else if (iocb->ki_flags & IOCB_DIRECT) {
 		num_written = __btrfs_direct_write(iocb, from);
 	} else {
 		num_written = btrfs_buffered_write(iocb, from);
