xfs_file_buffered_aio_write(): switch to generic_perform_write()

	const struct iovec	*iovp,

	unsigned long		nr_segs,

	loff_t			pos,

	size_t			ocount)

	size_t			count)

{

	struct file		*file = iocb->ki_filp;

	struct address_space	*mapping = file->f_mapping;

	ssize_t			ret;

	int			enospc = 0;

	int			iolock = XFS_IOLOCK_EXCL;

	size_t			count = ocount;

	struct iov_iter		from;

	xfs_rw_ilock(ip, iolock);

	if (ret)

		goto out;

	iov_iter_init(&from, iovp, nr_segs, count, 0);

	/* We can write back this queue in page reclaim */

	current->backing_dev_info = mapping->backing_dev_info;

write_retry:

	trace_xfs_file_buffered_write(ip, count, iocb->ki_pos, 0);

	ret = generic_file_buffered_write(iocb, iovp, nr_segs,

			pos, count, 0);

	ret = generic_perform_write(file, &from, pos);

	if (likely(ret >= 0))

		iocb->ki_pos = pos + ret;

	/*

	 * If we just got an ENOSPC, try to write back all dirty inodes to

	 * convert delalloc space to free up some of the excess reserved