diff --git a/fs/iomap.c b/fs/iomap.c
index 13dd413..93d36fd 100644
--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -24,6 +24,7 @@
 #include <linux/uio.h>
 #include <linux/backing-dev.h>
 #include <linux/buffer_head.h>
+#include <linux/task_io_accounting_ops.h>
 #include <linux/dax.h>
 #include "internal.h"
 
@@ -584,3 +585,375 @@ int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fi,
 	return 0;
 }
 EXPORT_SYMBOL_GPL(iomap_fiemap);
+
+/*
+ * Private flags for iomap_dio, must not overlap with the public ones in
+ * iomap.h:
+ */
+#define IOMAP_DIO_WRITE		(1 << 30)
+#define IOMAP_DIO_DIRTY	(1 << 31)
+
+struct iomap_dio {
+	struct kiocb		*iocb;
+	iomap_dio_end_io_t	*end_io;
+	loff_t			i_size;
+	loff_t			size;
+	atomic_t		ref;
+	unsigned		flags;
+	int			error;
+
+	union {
+		/* used during submission and for synchronous completion: */
+		struct {
+			struct iov_iter		*iter;
+			struct task_struct	*waiter;
+			struct request_queue	*last_queue;
+			blk_qc_t		cookie;
+		} submit;
+
+		/* used for aio completion: */
+		struct {
+			struct work_struct	work;
+		} aio;
+	};
+};
+
+static ssize_t iomap_dio_complete(struct iomap_dio *dio)
+{
+	struct kiocb *iocb = dio->iocb;
+	ssize_t ret;
+
+	if (dio->end_io) {
+		ret = dio->end_io(iocb,
+				dio->error ? dio->error : dio->size,
+				dio->flags);
+	} else {
+		ret = dio->error;
+	}
+
+	if (likely(!ret)) {
+		ret = dio->size;
+		/* check for short read */
+		if (iocb->ki_pos + ret > dio->i_size &&
+		    !(dio->flags & IOMAP_DIO_WRITE))
+			ret = dio->i_size - iocb->ki_pos;
+		iocb->ki_pos += ret;
+	}
+
+	inode_dio_end(file_inode(iocb->ki_filp));
+	kfree(dio);
+
+	return ret;
+}
+
+static void iomap_dio_complete_work(struct work_struct *work)
+{
+	struct iomap_dio *dio = container_of(work, struct iomap_dio, aio.work);
+	struct kiocb *iocb = dio->iocb;
+	bool is_write = (dio->flags & IOMAP_DIO_WRITE);
+	ssize_t ret;
+
+	ret = iomap_dio_complete(dio);
+	if (is_write && ret > 0)
+		ret = generic_write_sync(iocb, ret);
+	iocb->ki_complete(iocb, ret, 0);
+}
+
+/*
+ * Set an error in the dio if none is set yet.  We have to use cmpxchg
+ * as the submission context and the completion context(s) can race to
+ * update the error.
+ */
+static inline void iomap_dio_set_error(struct iomap_dio *dio, int ret)
+{
+	cmpxchg(&dio->error, 0, ret);
+}
+
+static void iomap_dio_bio_end_io(struct bio *bio)
+{
+	struct iomap_dio *dio = bio->bi_private;
+	bool should_dirty = (dio->flags & IOMAP_DIO_DIRTY);
+
+	if (bio->bi_error)
+		iomap_dio_set_error(dio, bio->bi_error);
+
+	if (atomic_dec_and_test(&dio->ref)) {
+		if (is_sync_kiocb(dio->iocb)) {
+			struct task_struct *waiter = dio->submit.waiter;
+
+			WRITE_ONCE(dio->submit.waiter, NULL);
+			wake_up_process(waiter);
+		} else if (dio->flags & IOMAP_DIO_WRITE) {
+			struct inode *inode = file_inode(dio->iocb->ki_filp);
+
+			INIT_WORK(&dio->aio.work, iomap_dio_complete_work);
+			queue_work(inode->i_sb->s_dio_done_wq, &dio->aio.work);
+		} else {
+			iomap_dio_complete_work(&dio->aio.work);
+		}
+	}
+
+	if (should_dirty) {
+		bio_check_pages_dirty(bio);
+	} else {
+		struct bio_vec *bvec;
+		int i;
+
+		bio_for_each_segment_all(bvec, bio, i)
+			put_page(bvec->bv_page);
+		bio_put(bio);
+	}
+}
+
+static blk_qc_t
+iomap_dio_zero(struct iomap_dio *dio, struct iomap *iomap, loff_t pos,
+		unsigned len)
+{
+	struct page *page = ZERO_PAGE(0);
+	struct bio *bio;
+
+	bio = bio_alloc(GFP_KERNEL, 1);
+	bio->bi_bdev = iomap->bdev;
+	bio->bi_iter.bi_sector =
+		iomap->blkno + ((pos - iomap->offset) >> 9);
+	bio->bi_private = dio;
+	bio->bi_end_io = iomap_dio_bio_end_io;
+
+	get_page(page);
+	if (bio_add_page(bio, page, len, 0) != len)
+		BUG();
+	bio_set_op_attrs(bio, REQ_OP_WRITE, WRITE_ODIRECT);
+
+	atomic_inc(&dio->ref);
+	return submit_bio(bio);
+}
+
+static loff_t
+iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
+		void *data, struct iomap *iomap)
+{
+	struct iomap_dio *dio = data;
+	unsigned blkbits = blksize_bits(bdev_logical_block_size(iomap->bdev));
+	unsigned fs_block_size = (1 << inode->i_blkbits), pad;
+	unsigned align = iov_iter_alignment(dio->submit.iter);
+	struct iov_iter iter;
+	struct bio *bio;
+	bool need_zeroout = false;
+	int nr_pages, ret;
+
+	if ((pos | length | align) & ((1 << blkbits) - 1))
+		return -EINVAL;
+
+	switch (iomap->type) {
+	case IOMAP_HOLE:
+		if (WARN_ON_ONCE(dio->flags & IOMAP_DIO_WRITE))
+			return -EIO;
+		/*FALLTHRU*/
+	case IOMAP_UNWRITTEN:
+		if (!(dio->flags & IOMAP_DIO_WRITE)) {
+			iov_iter_zero(length, dio->submit.iter);
+			dio->size += length;
+			return length;
+		}
+		dio->flags |= IOMAP_DIO_UNWRITTEN;
+		need_zeroout = true;
+		break;
+	case IOMAP_MAPPED:
+		if (iomap->flags & IOMAP_F_SHARED)
+			dio->flags |= IOMAP_DIO_COW;
+		if (iomap->flags & IOMAP_F_NEW)
+			need_zeroout = true;
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		return -EIO;
+	}
+
+	/*
+	 * Operate on a partial iter trimmed to the extent we were called for.
+	 * We'll update the iter in the dio once we're done with this extent.
+	 */
+	iter = *dio->submit.iter;
+	iov_iter_truncate(&iter, length);
+
+	nr_pages = iov_iter_npages(&iter, BIO_MAX_PAGES);
+	if (nr_pages <= 0)
+		return nr_pages;
+
+	if (need_zeroout) {
+		/* zero out from the start of the block to the write offset */
+		pad = pos & (fs_block_size - 1);
+		if (pad)
+			iomap_dio_zero(dio, iomap, pos - pad, pad);
+	}
+
+	do {
+		if (dio->error)
+			return 0;
+
+		bio = bio_alloc(GFP_KERNEL, nr_pages);
+		bio->bi_bdev = iomap->bdev;
+		bio->bi_iter.bi_sector =
+			iomap->blkno + ((pos - iomap->offset) >> 9);
+		bio->bi_private = dio;
+		bio->bi_end_io = iomap_dio_bio_end_io;
+
+		ret = bio_iov_iter_get_pages(bio, &iter);
+		if (unlikely(ret)) {
+			bio_put(bio);
+			return ret;
+		}
+
+		if (dio->flags & IOMAP_DIO_WRITE) {
+			bio_set_op_attrs(bio, REQ_OP_WRITE, WRITE_ODIRECT);
+			task_io_account_write(bio->bi_iter.bi_size);
+		} else {
+			bio_set_op_attrs(bio, REQ_OP_READ, 0);
+			if (dio->flags & IOMAP_DIO_DIRTY)
+				bio_set_pages_dirty(bio);
+		}
+
+		dio->size += bio->bi_iter.bi_size;
+		pos += bio->bi_iter.bi_size;
+
+		nr_pages = iov_iter_npages(&iter, BIO_MAX_PAGES);
+
+		atomic_inc(&dio->ref);
+
+		dio->submit.last_queue = bdev_get_queue(iomap->bdev);
+		dio->submit.cookie = submit_bio(bio);
+	} while (nr_pages);
+
+	if (need_zeroout) {
+		/* zero out from the end of the write to the end of the block */
+		pad = pos & (fs_block_size - 1);
+		if (pad)
+			iomap_dio_zero(dio, iomap, pos, fs_block_size - pad);
+	}
+
+	iov_iter_advance(dio->submit.iter, length);
+	return length;
+}
+
+ssize_t
+iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter, struct iomap_ops *ops,
+		iomap_dio_end_io_t end_io)
+{
+	struct address_space *mapping = iocb->ki_filp->f_mapping;
+	struct inode *inode = file_inode(iocb->ki_filp);
+	size_t count = iov_iter_count(iter);
+	loff_t pos = iocb->ki_pos, end = iocb->ki_pos + count - 1, ret = 0;
+	unsigned int flags = IOMAP_DIRECT;
+	struct blk_plug plug;
+	struct iomap_dio *dio;
+
+	lockdep_assert_held(&inode->i_rwsem);
+
+	if (!count)
+		return 0;
+
+	dio = kmalloc(sizeof(*dio), GFP_KERNEL);
+	if (!dio)
+		return -ENOMEM;
+
+	dio->iocb = iocb;
+	atomic_set(&dio->ref, 1);
+	dio->size = 0;
+	dio->i_size = i_size_read(inode);
+	dio->end_io = end_io;
+	dio->error = 0;
+	dio->flags = 0;
+
+	dio->submit.iter = iter;
+	if (is_sync_kiocb(iocb)) {
+		dio->submit.waiter = current;
+		dio->submit.cookie = BLK_QC_T_NONE;
+		dio->submit.last_queue = NULL;
+	}
+
+	if (iov_iter_rw(iter) == READ) {
+		if (pos >= dio->i_size)
+			goto out_free_dio;
+
+		if (iter->type == ITER_IOVEC)
+			dio->flags |= IOMAP_DIO_DIRTY;
+	} else {
+		dio->flags |= IOMAP_DIO_WRITE;
+		flags |= IOMAP_WRITE;
+	}
+
+	if (mapping->nrpages) {
+		ret = filemap_write_and_wait_range(mapping, iocb->ki_pos, end);
+		if (ret)
+			goto out_free_dio;
+
+		ret = invalidate_inode_pages2_range(mapping,
+				iocb->ki_pos >> PAGE_SHIFT, end >> PAGE_SHIFT);
+		WARN_ON_ONCE(ret);
+		ret = 0;
+	}
+
+	inode_dio_begin(inode);
+
+	blk_start_plug(&plug);
+	do {
+		ret = iomap_apply(inode, pos, count, flags, ops, dio,
+				iomap_dio_actor);
+		if (ret <= 0) {
+			/* magic error code to fall back to buffered I/O */
+			if (ret == -ENOTBLK)
+				ret = 0;
+			break;
+		}
+		pos += ret;
+	} while ((count = iov_iter_count(iter)) > 0);
+	blk_finish_plug(&plug);
+
+	if (ret < 0)
+		iomap_dio_set_error(dio, ret);
+
+	if (ret >= 0 && iov_iter_rw(iter) == WRITE && !is_sync_kiocb(iocb) &&
+			!inode->i_sb->s_dio_done_wq) {
+		ret = sb_init_dio_done_wq(inode->i_sb);
+		if (ret < 0)
+			iomap_dio_set_error(dio, ret);
+	}
+
+	if (!atomic_dec_and_test(&dio->ref)) {
+		if (!is_sync_kiocb(iocb))
+			return -EIOCBQUEUED;
+
+		for (;;) {
+			set_current_state(TASK_UNINTERRUPTIBLE);
+			if (!READ_ONCE(dio->submit.waiter))
+				break;
+
+			if (!(iocb->ki_flags & IOCB_HIPRI) ||
+			    !dio->submit.last_queue ||
+			    !blk_poll(dio->submit.last_queue,
+					dio->submit.cookie))
+				io_schedule();
+		}
+		__set_current_state(TASK_RUNNING);
+	}
+
+	/*
+	 * Try again to invalidate clean pages which might have been cached by
+	 * non-direct readahead, or faulted in by get_user_pages() if the source
+	 * of the write was an mmap'ed region of the file we're writing.  Either
+	 * one is a pretty crazy thing to do, so we don't support it 100%.  If
+	 * this invalidation fails, tough, the write still worked...
+	 */
+	if (iov_iter_rw(iter) == WRITE && mapping->nrpages) {
+		ret = invalidate_inode_pages2_range(mapping,
+				iocb->ki_pos >> PAGE_SHIFT, end >> PAGE_SHIFT);
+		WARN_ON_ONCE(ret);
+	}
+
+	return iomap_dio_complete(dio);
+
+out_free_dio:
+	kfree(dio);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(iomap_dio_rw);
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index f185156..a4c94b8 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -50,6 +50,7 @@ struct iomap {
 #define IOMAP_ZERO		(1 << 1) /* zeroing operation, may skip holes */
 #define IOMAP_REPORT		(1 << 2) /* report extent status, e.g. FIEMAP */
 #define IOMAP_FAULT		(1 << 3) /* mapping for page fault */
+#define IOMAP_DIRECT		(1 << 4) /* direct I/O */
 
 struct iomap_ops {
 	/*
@@ -83,4 +84,14 @@ int iomap_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
 int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 		loff_t start, loff_t len, struct iomap_ops *ops);
 
+/*
+ * Flags for direct I/O ->end_io:
+ */
+#define IOMAP_DIO_UNWRITTEN	(1 << 0)	/* covers unwritten extent(s) */
+#define IOMAP_DIO_COW		(1 << 1)	/* covers COW extent(s) */
+typedef int (iomap_dio_end_io_t)(struct kiocb *iocb, ssize_t ret,
+		unsigned flags);
+ssize_t iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
+		struct iomap_ops *ops, iomap_dio_end_io_t end_io);
+
 #endif /* LINUX_IOMAP_H */
