btrfs: use predefined limits for calculating maximum number of pages for compression

	unsigned long nr_pages;

	unsigned long total_compressed = 0;

	unsigned long total_in = 0;

	unsigned long max_compressed = SZ_128K;

	unsigned long max_uncompressed = SZ_128K;

	int i;

	int will_compress;

	int compress_type = fs_info->compress_type;

again:

	will_compress = 0;

	nr_pages = (end >> PAGE_SHIFT) - (start >> PAGE_SHIFT) + 1;

	nr_pages = min_t(unsigned long, nr_pages, SZ_128K / PAGE_SIZE);

	BUILD_BUG_ON((BTRFS_MAX_COMPRESSED % PAGE_SIZE) != 0);

	nr_pages = min_t(unsigned long, nr_pages,

			BTRFS_MAX_COMPRESSED / PAGE_SIZE);

	/*

	 * we don't want to send crud past the end of i_size through

	   (start > 0 || end + 1 < BTRFS_I(inode)->disk_i_size))

		goto cleanup_and_bail_uncompressed;

	total_compressed = min(total_compressed, max_uncompressed);

	total_compressed = min_t(unsigned long, total_compressed,

			BTRFS_MAX_UNCOMPRESSED);

	num_bytes = ALIGN(end - start + 1, blocksize);

	num_bytes = max(blocksize,  num_bytes);

	total_in = 0;

					   &nr_pages,

					   &total_in,

					   &total_compressed,

					   max_compressed);

					   BTRFS_MAX_COMPRESSED);

		if (!ret) {

			unsigned long offset = total_compressed &