ceph/src/osd/SnapMapper.h

   1 // -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
   2 // vim: ts=8 sw=2 smarttab
   3 /*
   4  * Ceph - scalable distributed file system
   5  *
   6  * Copyright (C) 2013 Inktank Storage, Inc.
   7  *
   8  * This is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License version 2.1, as published by the Free Software
  11  * Foundation.  See file COPYING.
  12  *
  13  */
  14
  15 #ifndef SNAPMAPPER_H
  16 #define SNAPMAPPER_H
  17
  18 #include <string>
  19 #include <set>
  20 #include <utility>
  21 #include <string.h>
  22
  23 #include "common/map_cacher.hpp"
  24 #include "common/hobject.h"
  25 #include "include/buffer.h"
  26 #include "include/encoding.h"
  27 #include "include/object.h"
  28 #include "os/ObjectStore.h"
  29
  30 class OSDriver : public MapCacher::StoreDriver<std::string, bufferlist> {
  31   ObjectStore *os;
  32   coll_t cid;
  33   ghobject_t hoid;
  34
  35 public:
  36   class OSTransaction : public MapCacher::Transaction<std::string, bufferlist> {
  37     friend class OSDriver;
  38     coll_t cid;
  39     ghobject_t hoid;
  40     ObjectStore::Transaction *t;
  41     OSTransaction(
  42       coll_t cid,
  43       const ghobject_t &hoid,
  44       ObjectStore::Transaction *t)
  45       : cid(cid), hoid(hoid), t(t) {}
  46   public:
  47     void set_keys(
  48       const std::map<std::string, bufferlist> &to_set) override {
  49       t->omap_setkeys(cid, hoid, to_set);
  50     }
  51     void remove_keys(
  52       const std::set<std::string> &to_remove) override {
  53       t->omap_rmkeys(cid, hoid, to_remove);
  54     }
  55     void add_callback(
  56       Context *c) override {
  57       t->register_on_applied(c);
  58     }
  59   };
  60
  61   OSTransaction get_transaction(
  62     ObjectStore::Transaction *t) {
  63     return OSTransaction(cid, hoid, t);
  64   }
  65
  66   OSDriver(ObjectStore *os, coll_t cid, const ghobject_t &hoid) :
  67     os(os), cid(cid), hoid(hoid) {}
  68   int get_keys(
  69     const std::set<std::string> &keys,
  70     std::map<std::string, bufferlist> *out) override;
  71   int get_next(
  72     const std::string &key,
  73     pair<std::string, bufferlist> *next) override;
  74 };
  75
  76 /**
  77  * SnapMapper
  78  *
  79  * Manages two mappings:
  80  *  1) hobject_t -> {snapid}
  81  *  2) snapid -> {hobject_t}
  82  *
  83  * We accomplish this using two sets of keys:
  84  *  1) OBJECT_PREFIX + obj.str() -> encoding of object_snaps
  85  *  2) MAPPING_PREFIX + snapid_t + obj.str() -> encoding of pair<snapid_t, obj>
  86  *
  87  * The on disk strings and encodings are implemented in to_raw, to_raw_key,
  88  * from_raw, to_object_key.
  89  *
  90  * The object -> {snapid} mapping is primarily included so that the
  91  * SnapMapper state can be verified against the external PG state during
  92  * scrub etc.
  93  *
  94  * The 2) mapping is arranged such that all objects in a particular
  95  * snap will sort together, and so that all objects in a pg for a
  96  * particular snap will group under up to 8 prefixes.
  97  */
  98 class SnapMapper {
  99 public:
 100   CephContext* cct;
 101   struct object_snaps {
 102     hobject_t oid;
 103     std::set<snapid_t> snaps;
 104     object_snaps(hobject_t oid, const std::set<snapid_t> &snaps)
 105       : oid(oid), snaps(snaps) {}
 106     object_snaps() {}
 107     void encode(bufferlist &bl) const;
 108     void decode(bufferlist::iterator &bp);
 109   };
 110
 111 private:
 112   MapCacher::MapCacher<std::string, bufferlist> backend;
 113
 114   static const std::string MAPPING_PREFIX;
 115   static const std::string OBJECT_PREFIX;
 116
 117   static std::string get_prefix(snapid_t snap);
 118
 119   std::string to_raw_key(
 120     const std::pair<snapid_t, hobject_t> &to_map);
 121
 122   std::pair<std::string, bufferlist> to_raw(
 123     const std::pair<snapid_t, hobject_t> &to_map);
 124
 125   static bool is_mapping(const std::string &to_test);
 126
 127   std::pair<snapid_t, hobject_t> from_raw(
 128     const std::pair<std::string, bufferlist> &image);
 129
 130   std::string to_object_key(const hobject_t &hoid);
 131
 132   int get_snaps(const hobject_t &oid, object_snaps *out);
 133
 134   void set_snaps(
 135     const hobject_t &oid,
 136     const object_snaps &out,
 137     MapCacher::Transaction<std::string, bufferlist> *t);
 138
 139   void clear_snaps(
 140     const hobject_t &oid,
 141     MapCacher::Transaction<std::string, bufferlist> *t);
 142
 143   // True if hoid belongs in this mapping based on mask_bits and match
 144   bool check(const hobject_t &hoid) const {
 145     return hoid.match(mask_bits, match);
 146   }
 147
 148   int _remove_oid(
 149     const hobject_t &oid,    ///< [in] oid to remove
 150     MapCacher::Transaction<std::string, bufferlist> *t ///< [out] transaction
 151     );
 152
 153 public:
 154   static string make_shard_prefix(shard_id_t shard) {
 155     if (shard == shard_id_t::NO_SHARD)
 156       return string();
 157     char buf[20];
 158     int r = snprintf(buf, sizeof(buf), ".%x", (int)shard);
 159     assert(r < (int)sizeof(buf));
 160     return string(buf, r) + '_';
 161   }
 162   uint32_t mask_bits;
 163   const uint32_t match;
 164   string last_key_checked;
 165   const int64_t pool;
 166   const shard_id_t shard;
 167   const string shard_prefix;
 168   SnapMapper(
 169     CephContext* cct,
 170     MapCacher::StoreDriver<std::string, bufferlist> *driver,
 171     uint32_t match,  ///< [in] pgid
 172     uint32_t bits,   ///< [in] current split bits
 173     int64_t pool,    ///< [in] pool
 174     shard_id_t shard ///< [in] shard
 175     )
 176     : cct(cct), backend(driver), mask_bits(bits), match(match), pool(pool),
 177       shard(shard), shard_prefix(make_shard_prefix(shard)) {
 178     update_bits(mask_bits);
 179   }
 180
 181   set<string> prefixes;
 182   /// Update bits in case of pg split
 183   void update_bits(
 184     uint32_t new_bits  ///< [in] new split bits
 185     ) {
 186     assert(new_bits >= mask_bits);
 187     mask_bits = new_bits;
 188     set<string> _prefixes = hobject_t::get_prefixes(
 189       mask_bits,
 190       match,
 191       pool);
 192     prefixes.clear();
 193     for (set<string>::iterator i = _prefixes.begin();
 194          i != _prefixes.end();
 195          ++i) {
 196       prefixes.insert(shard_prefix + *i);
 197     }
 198   }
 199
 200   /// Update snaps for oid, empty new_snaps removes the mapping
 201   int update_snaps(
 202     const hobject_t &oid,       ///< [in] oid to update
 203     const std::set<snapid_t> &new_snaps, ///< [in] new snap set
 204     const std::set<snapid_t> *old_snaps, ///< [in] old snaps (for debugging)
 205     MapCacher::Transaction<std::string, bufferlist> *t ///< [out] transaction
 206     ); ///@ return error, 0 on success
 207
 208   /// Add mapping for oid, must not already be mapped
 209   void add_oid(
 210     const hobject_t &oid,       ///< [in] oid to add
 211     const std::set<snapid_t>& new_snaps, ///< [in] snaps
 212     MapCacher::Transaction<std::string, bufferlist> *t ///< [out] transaction
 213     );
 214
 215   /// Returns first object with snap as a snap
 216   int get_next_objects_to_trim(
 217     snapid_t snap,              ///< [in] snap to check
 218     unsigned max,               ///< [in] max to get
 219     vector<hobject_t> *out      ///< [out] next objects to trim (must be empty)
 220     );  ///< @return error, -ENOENT if no more objects
 221
 222   /// Remove mapping for oid
 223   int remove_oid(
 224     const hobject_t &oid,    ///< [in] oid to remove
 225     MapCacher::Transaction<std::string, bufferlist> *t ///< [out] transaction
 226     ); ///< @return error, -ENOENT if the object is not mapped
 227
 228   /// Get snaps for oid
 229   int get_snaps(
 230     const hobject_t &oid,     ///< [in] oid to get snaps for
 231     std::set<snapid_t> *snaps ///< [out] snaps
 232     ); ///< @return error, -ENOENT if oid is not recorded
 233 };
 234 WRITE_CLASS_ENCODER(SnapMapper::object_snaps)
 235
 236 #endif