fs: add vfs_iter_{read,write} helpers

Simple helpers that pass an arbitrary iov_iter to filesystems.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 46 insertions, 0 deletions

diff --git a/fs/read_write.c b/fs/read_write.c
index c0805c93b6fa..ab4f26a7d5cb 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -333,6 +333,52 @@ out_putf:
 }
 #endif
 
+ssize_t vfs_iter_read(struct file *file, struct iov_iter *iter, loff_t *ppos)
+{
+	struct kiocb kiocb;
+	ssize_t ret;
+
+	if (!file->f_op->read_iter)
+		return -EINVAL;
+
+	init_sync_kiocb(&kiocb, file);
+	kiocb.ki_pos = *ppos;
+	kiocb.ki_nbytes = iov_iter_count(iter);
+
+	iter->type |= READ;
+	ret = file->f_op->read_iter(&kiocb, iter);
+	if (ret == -EIOCBQUEUED)
+		ret = wait_on_sync_kiocb(&kiocb);
+
+	if (ret > 0)
+		*ppos = kiocb.ki_pos;
+	return ret;
+}
+EXPORT_SYMBOL(vfs_iter_read);
+
+ssize_t vfs_iter_write(struct file *file, struct iov_iter *iter, loff_t *ppos)
+{
+	struct kiocb kiocb;
+	ssize_t ret;
+
+	if (!file->f_op->write_iter)
+		return -EINVAL;
+
+	init_sync_kiocb(&kiocb, file);
+	kiocb.ki_pos = *ppos;
+	kiocb.ki_nbytes = iov_iter_count(iter);
+
+	iter->type |= WRITE;
+	ret = file->f_op->write_iter(&kiocb, iter);
+	if (ret == -EIOCBQUEUED)
+		ret = wait_on_sync_kiocb(&kiocb);
+
+	if (ret > 0)
+		*ppos = kiocb.ki_pos;
+	return ret;
+}
+EXPORT_SYMBOL(vfs_iter_write);
+
 /*
  * rw_verify_area doesn't like huge counts. We limit
  * them to something that fits in "int" so that others