Re: [REVIEW] Re: Compression of full-page-writes

I had a look at code. I have few minor points,

+           bkpb.fork_flags |= BKPBLOCK_HAS_IMAGE;

+

+           if (is_compressed)

            {

-               rdt_datas_last->data = page;

-               rdt_datas_last->len = BLCKSZ;

+               /* compressed block information */

+               bimg.length = compress_len;

+               bimg.extra_data = hole_offset;

+               bimg.extra_data |= XLR_BLCK_COMPRESSED_MASK;

For consistency with the existing code , how about renaming the macro XLR_BLCK_COMPRESSED_MASK as BKPBLOCK_HAS_COMPRESSED_IMAGE on the lines of BKPBLOCK_HAS_IMAGE.

+               blk->hole_offset = extra_data & ~XLR_BLCK_COMPRESSED_MASK;

Here , I think that having the mask as BKPBLOCK_HOLE_OFFSET_MASK will be more indicative of the fact that lower 15 bits of extra_data field comprises of hole_offset value. This suggestion is also just to achieve consistency with the existing BKPBLOCK_FORK_MASK for fork_flags field.

And comment typo

+            * First try to compress block, filling in the page hole with zeros

+            * to improve the compression of the whole. If the block is considered

+            * as incompressible, complete the block header information as if

+            * nothing happened.

As hole is no longer being compressed, this needs to be changed.