Revert "fs: remove dio_end_io()"

This reverts commit b75b7ca7.

The patch restores a helper that was not necessary after direct IO port
to iomap infrastructure, which gets reverted.
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/direct-io.c

@@ -386,6 +386,25 @@ static void dio_bio_end_io(struct bio *bio)
 	spin_unlock_irqrestore(&dio->bio_lock, flags);
 }
 
+/**
+ * dio_end_io - handle the end io action for the given bio
+ * @bio: The direct io bio thats being completed
+ *
+ * This is meant to be called by any filesystem that uses their own dio_submit_t
+ * so that the DIO specific endio actions are dealt with after the filesystem
+ * has done it's completion work.
+ */
+void dio_end_io(struct bio *bio)
+{
+	struct dio *dio = bio->bi_private;
+
+	if (dio->is_async)
+		dio_bio_end_aio(bio);
+	else
+		dio_bio_end_io(bio);
+}
+EXPORT_SYMBOL_GPL(dio_end_io);
+
 static inline void
 dio_bio_alloc(struct dio *dio, struct dio_submit *sdio,
 	      struct block_device *bdev,

include/linux/fs.h

@@ -3187,6 +3187,8 @@ enum {
 	DIO_SKIP_HOLES	= 0x02,
 };
 
+void dio_end_io(struct bio *bio);
+
 ssize_t __blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
 			     struct block_device *bdev, struct iov_iter *iter,
 			     get_block_t get_block,