ceph/src/os/filestore/FDCache.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 CEPH_FDCACHE_H
  16 #define CEPH_FDCACHE_H
  17
  18 #include <memory>
  19 #include <errno.h>
  20 #include <cstdio>
  21 #include "common/config_obs.h"
  22 #include "common/hobject.h"
  23 #include "common/shared_cache.hpp"
  24 #include "include/compat.h"
  25 #include "include/intarith.h"
  26
  27 /**
  28  * FD Cache
  29  */
  30 class FDCache : public md_config_obs_t {
  31 public:
  32   /**
  33    * FD
  34    *
  35    * Wrapper for an fd.  Destructor closes the fd.
  36    */
  37   class FD {
  38   public:
  39     const int fd;
  40     explicit FD(int _fd) : fd(_fd) {
  41       ceph_assert(_fd >= 0);
  42     }
  43     int operator*() const {
  44       return fd;
  45     }
  46     ~FD() {
  47       VOID_TEMP_FAILURE_RETRY(::close(fd));
  48     }
  49   };
  50
  51 private:
  52   CephContext *cct;
  53   const int registry_shards;
  54   SharedLRU<ghobject_t, FD> *registry;
  55
  56 public:
  57   explicit FDCache(CephContext *cct) : cct(cct),
  58   registry_shards(std::max<int64_t>(cct->_conf->filestore_fd_cache_shards, 1)) {
  59     ceph_assert(cct);
  60     cct->_conf.add_observer(this);
  61     registry = new SharedLRU<ghobject_t, FD>[registry_shards];
  62     for (int i = 0; i < registry_shards; ++i) {
  63       registry[i].set_cct(cct);
  64       registry[i].set_size(
  65           std::max<int64_t>((cct->_conf->filestore_fd_cache_size / registry_shards), 1));
  66     }
  67   }
  68   ~FDCache() override {
  69     cct->_conf.remove_observer(this);
  70     delete[] registry;
  71   }
  72   typedef std::shared_ptr<FD> FDRef;
  73
  74   FDRef lookup(const ghobject_t &hoid) {
  75     int registry_id = hoid.hobj.get_hash() % registry_shards;
  76     return registry[registry_id].lookup(hoid);
  77   }
  78
  79   FDRef add(const ghobject_t &hoid, int fd, bool *existed) {
  80     int registry_id = hoid.hobj.get_hash() % registry_shards;
  81     return registry[registry_id].add(hoid, new FD(fd), existed);
  82   }
  83
  84   /// clear cached fd for hoid, subsequent lookups will get an empty FD
  85   void clear(const ghobject_t &hoid) {
  86     int registry_id = hoid.hobj.get_hash() % registry_shards;
  87     registry[registry_id].purge(hoid);
  88   }
  89
  90   /// md_config_obs_t
  91   const char** get_tracked_conf_keys() const override {
  92     static const char* KEYS[] = {
  93       "filestore_fd_cache_size",
  94       NULL
  95     };
  96     return KEYS;
  97   }
  98   void handle_conf_change(const ConfigProxy& conf,
  99                           const std::set<std::string> &changed) override {
 100     if (changed.count("filestore_fd_cache_size")) {
 101       for (int i = 0; i < registry_shards; ++i)
 102         registry[i].set_size(
 103               std::max<int64_t>((conf->filestore_fd_cache_size / registry_shards), 1));
 104     }
 105   }
 106
 107 };
 108 typedef FDCache::FDRef FDRef;
 109
 110 #endif