ceph/src/mds/StrayManager.h

   1 // vim: ts=8 sw=2 smarttab
   2 /*
   3  * Ceph - scalable distributed file system
   4  *
   5  * Copyright (C) 2015 Red Hat
   6  *
   7  * This is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License version 2.1, as published by the Free Software
  10  * Foundation.  See file COPYING.
  11  *
  12  */
  13
  14 #ifndef STRAY_MANAGER_H
  15 #define STRAY_MANAGER_H
  16
  17 #include "include/common_fwd.h"
  18 #include "include/elist.h"
  19 #include <list>
  20 #include "mds/PurgeQueue.h"
  21
  22 class MDSRank;
  23 class CInode;
  24 class CDentry;
  25
  26 class StrayManager
  27 {
  28   // My public interface is for consumption by MDCache
  29 public:
  30   explicit StrayManager(MDSRank *mds, PurgeQueue &purge_queue_);
  31   void set_logger(PerfCounters *l) {logger = l;}
  32   void activate();
  33
  34   bool eval_stray(CDentry *dn);
  35
  36   void set_num_strays(uint64_t num);
  37   uint64_t get_num_strays() const { return num_strays; }
  38
  39   /**
  40    * Queue dentry for later evaluation. (evaluate it while not in the
  41    * middle of another metadata operation)
  42    */
  43   void queue_delayed(CDentry *dn);
  44
  45   /**
  46    * Eval strays in the delayed_eval_stray list
  47    */
  48   void advance_delayed();
  49
  50   /**
  51    * Remote dentry potentially points to a stray. When it is touched,
  52    * call in here to evaluate it for migration (move a stray residing
  53    * on another MDS to this MDS) or reintegration (move a stray dentry's
  54    * inode into a non-stray hardlink dentry and clean up the stray).
  55    *
  56    * @param stray_dn a stray dentry whose inode has been referenced
  57    *                 by a remote dentry
  58    * @param remote_dn (optional) which remote dentry was touched
  59    *                  in an operation that led us here: this is used
  60    *                  as a hint for which remote to reintegrate into
  61    *                  if there are multiple remotes.
  62    */
  63   void eval_remote(CDentry *remote_dn);
  64
  65   /**
  66    * Given a dentry within one of my stray directories,
  67    * send it off to a stray directory in another MDS.
  68    *
  69    * This is for use:
  70    *  * Case A: when shutting down a rank, we migrate strays
  71    *    away from ourselves rather than waiting for purge
  72    *  * Case B: when a client request has a trace that refers to
  73    *    a stray inode on another MDS, we migrate that inode from
  74    *    there to here, in order that we can later re-integrate it
  75    *    here.
  76    *
  77    * In case B, the receiver should be calling into eval_stray
  78    * on completion of mv (i.e. inode put), resulting in a subsequent
  79    * reintegration.
  80    */
  81   void migrate_stray(CDentry *dn, mds_rank_t dest);
  82
  83   /**
  84    * Update stats to reflect a newly created stray dentry. Needed
  85    * because stats on strays live here, but creation happens
  86    * in Server or MDCache. For our purposes "creation" includes
  87    * loading a stray from a dirfrag and migrating a stray from
  88    * another MDS, in addition to creations per-se.
  89    */
  90   void notify_stray_created();
  91
  92   /**
  93    * Update stats to reflect a removed stray dentry. Needed because
  94    * stats on strays live here, but removal happens in Server or
  95    * MDCache. Also includes migration (rename) of strays from
  96    * this MDS to another MDS.
  97    */
  98   void notify_stray_removed();
  99
 100 protected:
 101   friend class StrayManagerIOContext;
 102   friend class StrayManagerLogContext;
 103   friend class StrayManagerContext;
 104
 105   friend class C_StraysFetched;
 106   friend class C_OpenSnapParents;
 107   friend class C_PurgeStrayLogged;
 108   friend class C_TruncateStrayLogged;
 109   friend class C_IO_PurgeStrayPurged;
 110
 111   void truncate(CDentry *dn);
 112
 113   /**
 114    * Purge a dentry from a stray directory. This function
 115    * is called once eval_stray is satisfied and StrayManager
 116    * throttling is also satisfied. There is no going back
 117    * at this stage!
 118    */
 119   void purge(CDentry *dn);
 120
 121   /**
 122    * Completion handler for a Filer::purge on a stray inode.
 123    */
 124   void _purge_stray_purged(CDentry *dn, bool only_head);
 125
 126   void _purge_stray_logged(CDentry *dn, version_t pdv, LogSegment *ls);
 127
 128   /**
 129    * Callback: we have logged the update to an inode's metadata
 130    * reflecting it's newly-zeroed length.
 131    */
 132   void _truncate_stray_logged(CDentry *dn, LogSegment *ls);
 133   /**
 134    * Call this on a dentry that has been identified as
 135    * eligible for purging. It will be passed on to PurgeQueue.
 136    */
 137   void enqueue(CDentry *dn, bool trunc);
 138   /**
 139    * Final part of enqueue() which we may have to retry
 140    * after opening snap parents.
 141    */
 142   void _enqueue(CDentry *dn, bool trunc);
 143
 144   /**
 145    * When hard links exist to an inode whose primary dentry
 146    * is unlinked, the inode gets a stray primary dentry.
 147    *
 148    * We may later "reintegrate" the inode into a remaining
 149    * non-stray dentry (one of what was previously a remote
 150    * dentry) by issuing a rename from the stray to the other
 151    * dentry.
 152    */
 153   void reintegrate_stray(CDentry *dn, CDentry *rlink);
 154
 155   /**
 156    * Evaluate a stray dentry for purging or reintegration.
 157    *
 158    * purging: If the inode has no linkage, and no more references, then
 159    *          we may decide to purge it.
 160    *
 161    * reintegration: If the inode still has linkage, then it means someone else
 162    *                (a hard link) is still referring to it, and we should
 163    *                think about reintegrating that inode into the remote dentry.
 164    *
 165    * @returns true if the dentry will be purged (caller should never
 166    *          take more refs after this happens), else false.
 167    */
 168   bool _eval_stray(CDentry *dn);
 169
 170   void _eval_stray_remote(CDentry *stray_dn, CDentry *remote_dn);
 171
 172   // Has passed through eval_stray and still has refs
 173   elist<CDentry*> delayed_eval_stray;
 174
 175   // strays that have been trimmed from cache
 176   std::set<std::string> trimmed_strays;
 177
 178   // Global references for doing I/O
 179   MDSRank *mds;
 180   PerfCounters *logger = nullptr;
 181
 182   bool started = false;
 183
 184   // Stray dentries for this rank (including those not in cache)
 185   uint64_t num_strays = 0;
 186
 187   // Stray dentries
 188   uint64_t num_strays_delayed = 0;
 189   /**
 190    * Entries that have entered enqueue() but not been persistently
 191    * recorded by PurgeQueue yet
 192    */
 193   uint64_t num_strays_enqueuing = 0;
 194
 195   PurgeQueue &purge_queue;
 196 };
 197 #endif  // STRAY_MANAGER_H