f2fs: avoid memory allocation failure due to a long length

static int __exchange_data_block(struct inode *src_inode,

			struct inode *dst_inode, pgoff_t src, pgoff_t dst,

			int len, bool full)

			pgoff_t len, bool full)

{

	block_t *src_blkaddr;

	int *do_replace;

	pgoff_t olen;

	int ret;

	src_blkaddr = f2fs_kvzalloc(sizeof(block_t) * len, GFP_KERNEL);

	while (len) {

		olen = min((pgoff_t)4 * ADDRS_PER_BLOCK, len);

		src_blkaddr = f2fs_kvzalloc(sizeof(block_t) * olen, GFP_KERNEL);

		if (!src_blkaddr)

			return -ENOMEM;

	do_replace = f2fs_kvzalloc(sizeof(int) * len, GFP_KERNEL);

		do_replace = f2fs_kvzalloc(sizeof(int) * olen, GFP_KERNEL);

		if (!do_replace) {

			kvfree(src_blkaddr);

			return -ENOMEM;

		}

	ret = __read_out_blkaddrs(src_inode, src_blkaddr, do_replace, src, len);

		ret = __read_out_blkaddrs(src_inode, src_blkaddr,

					do_replace, src, olen);

		if (ret)

			goto roll_back;

		ret = __clone_blkaddrs(src_inode, dst_inode, src_blkaddr,

					do_replace, src, dst, len, full);

					do_replace, src, dst, olen, full);

		if (ret)

			goto roll_back;

		src += olen;

		dst += olen;

		len -= olen;

		kvfree(src_blkaddr);

		kvfree(do_replace);

	}

	return 0;

roll_back: