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