[PATCH 22/22] block_dev: add support for read_iter, write_iter

[Dave Kleikamp <dave.kleikamp@oracle.com>]

From: Asias He <asias@redhat.com>

Use generic_file_read_iter for read_iter. Add blkdev_write_iter which is
based on blkdev_aio_write for write_iter.

Signed-off-by: Asias He <asias@redhat.com>
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
---
 fs/block_dev.c | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index ba3ed89..1a3aef9 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1593,6 +1593,21 @@ static long block_ioctl(struct file *file, unsigned cmd, unsigned long arg)
 	return blkdev_ioctl(bdev, mode, cmd, arg);
 }
 
+static ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *iter,
+				loff_t pos)
+{
+	ssize_t ret;
+	struct block_device *bdev = I_BDEV(iocb->ki_filp->f_mapping->host);
+
+	percpu_down_read(&bdev->bd_block_size_semaphore);
+
+	ret = generic_file_read_iter(iocb, iter, pos);
+
+	percpu_up_read(&bdev->bd_block_size_semaphore);
+
+	return ret;
+}
+
 ssize_t blkdev_aio_read(struct kiocb *iocb, const struct iovec *iov,
 			unsigned long nr_segs, loff_t pos)
 {
@@ -1609,6 +1624,25 @@ ssize_t blkdev_aio_read(struct kiocb *iocb, const struct iovec *iov,
 }
 EXPORT_SYMBOL_GPL(blkdev_aio_read);
 
+ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *iter, loff_t pos)
+{
+	struct file *file = iocb->ki_filp;
+	ssize_t ret;
+
+	BUG_ON(iocb->ki_pos != pos);
+
+	ret = __generic_file_write_iter(iocb, iter, &pos);
+	if (ret > 0 || ret == -EIOCBQUEUED) {
+		ssize_t err;
+
+		err = generic_write_sync(file, pos, ret);
+		if (err < 0 && ret > 0)
+			ret = err;
+	}
+	return ret;
+}
+EXPORT_SYMBOL_GPL(blkdev_write_iter);
+
 /*
  * Write data to the block device.  Only intended for the block device itself
  * and the raw driver which basically is a fake block device.
@@ -1693,6 +1727,8 @@ const struct file_operations def_blk_fops = {
 	.write		= do_sync_write,
   	.aio_read	= blkdev_aio_read,
 	.aio_write	= blkdev_aio_write,
+	.read_iter	= blkdev_read_iter,
+	.write_iter	= blkdev_write_iter,
 	.mmap		= blkdev_mmap,
 	.fsync		= blkdev_fsync,
 	.unlocked_ioctl	= block_ioctl,
-- 
1.7.12.3