From mboxrd@z Thu Jan  1 00:00:00 1970
From: Sage Weil <sage@newdream.net>
Subject: Re: Adding compression support for bluestore.
Date: Thu, 31 Mar 2016 17:56:18 -0400 (EDT)
Message-ID: <alpine.DEB.2.11.1603311746080.4670@cpach.fuggernut.com>
References: <56C1FCF3.4030505@mirantis.com> <CACJqLyb=X1i7tsYeKOEJRdJEEMBGvgW817eY5Bo9YBXDszUDmw@mail.gmail.com> <56C3BAA3.3070804@mirantis.com> <CY1PR0201MB1897E7F1DE04B5E4577B16EDE8A00@CY1PR0201MB1897.namprd02.prod.outlook.com>
 <alpine.DEB.2.11.1602220718380.13988@cpach.fuggernut.com> <56CDF40C.9060405@mirantis.com> <CY1PR0201MB1897BC7052AD6F7FB01DCAB4E8A50@CY1PR0201MB1897.namprd02.prod.outlook.com> <56D08E30.20308@mirantis.com> <alpine.DEB.2.11.1603151243030.32086@cpach.fuggernut.com>
 <56E9A727.1030400@mirantis.com> <alpine.DEB.2.11.1603161515360.14377@cpach.fuggernut.com> <56EACAAD.90002@mirantis.com> <alpine.DEB.2.11.1603171123090.14377@cpach.fuggernut.com> <56EC248E.3060502@mirantis.com> <CY1PR0201MB1897035E6E09FE518ACC2DDCE88D0@CY1PR0201MB1897.namprd02.prod.outlook.com>
 <56F013FB.4040002@mirantis.com> <alpine.DEB.2.11.1603211141560.23875@cpach.fuggernut.com> <56F3E157.2090004@mirantis.com>
Mime-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Return-path: <ceph-devel-owner@vger.kernel.org>
Received: from cobra.newdream.net ([66.33.216.30]:57914 "EHLO
	cobra.newdream.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1752003AbcCaV42 (ORCPT
	<rfc822;ceph-devel@vger.kernel.org>); Thu, 31 Mar 2016 17:56:28 -0400
In-Reply-To: <56F3E157.2090004@mirantis.com>
Sender: ceph-devel-owner@vger.kernel.org
List-ID: <ceph-devel.vger.kernel.org>
To: Igor Fedotov <ifedotov@mirantis.com>
Cc: Allen Samuels <Allen.Samuels@sandisk.com>, ceph-devel <ceph-devel@vger.kernel.org>

How about this:

// in the onode:
map<uint64_t, bluestore_lextent_t> data_map;
map<int, bluestore_blob_t> blob_map;

// in the enode
map<int, bluestore_blob_t> blob_map;

struct bluestore_lextent_t {
  enum {
    FLAG_SHARED = 1,        ///< pextent lives in enode
  };

  uint64_t logical_length;  ///< length of logical bytes we represent
  uint32_t pextent_id;      ///< id of pextent in onode or enode
  uint32_t x_off, x_len;    ///< relative portion of pextent with our data
  uint32_t flags;           ///< FLAG_*
};

struct bluestore_pextent_t {
  uint64_t offset;          ///< offset on disk
  uint64_t length;          ///< length on disk
};

struct bluestore_blob_t {
  enum {
    CSUM_XXHASH32 = 1,
    CSUM_XXHASH64 = 2,
    CSUM_CRC32C = 3,
    CSUM_CRC16 = 4,
  };
  enum {
    FLAG_IMMUTABLE = 1,     ///< no overwrites allowed
    FLAG_COMPRESSED = 2,    ///< extent is compressed; alg is in first byte of data
  };
  enum {
    COMP_ZLIB = 1,
    COMP_SNAPPY = 2,
    COMP_LZO = 3,
  };

  vector<bluestore_pextent_t> extents;  ///< extents on disk
  uint32_t logical_length;              ///< uncompressed length
  uint32_t flags;                       ///< FLAG_*
  uint8_t csum_type;                    ///< CSUM_*
  uint8_t csum_block_order;
  uint16_t num_refs;               ///< reference count (always 1 when in onode)
  vector<char> csum_data;          ///< opaque vector of csum data

  uint32_t get_ondisk_length() const {
    uint32_t len = 0;
    for (auto &p : extentes) {
      len += p.length;
    }
    return len;
  }

  uint32_t get_csum_block_size() const {
    return 1 << csum_block_order;
  }
  size_t get_csum_value_size() const {
    switch (csum_type) {
    case CSUM_XXHASH32: return 4;
    case CSUM_XXHASH64: return 8;
    case CSUM_CRC32C: return 4;
    case CSUM_CRC16: return 2;
    default: return 0;
    }
  }

  // assert (ondisk_length / csum_block_size) * csum_value_size ==
  // csum_data.length()
};