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// vim: ts=8 sw=2 smarttab
/*
* Ceph - scalable distributed file system
*
* Copyright (C) 2015 Red Hat
*
* This is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License version 2.1, as published by the Free Software
* Foundation. See file COPYING.
*
*/
#ifndef STRAY_MANAGER_H
#define STRAY_MANAGER_H
#include "include/common_fwd.h"
#include "include/elist.h"
#include <list>
#include "Mutation.h"
#include "PurgeQueue.h"
class MDSRank;
class CInode;
class CDentry;
class StrayManager
{
// My public interface is for consumption by MDCache
public:
explicit StrayManager(MDSRank *mds, PurgeQueue &purge_queue_);
void set_logger(PerfCounters *l) {logger = l;}
void activate();
bool eval_stray(CDentry *dn);
void set_num_strays(uint64_t num);
uint64_t get_num_strays() const { return num_strays; }
/**
* Queue dentry for later evaluation. (evaluate it while not in the
* middle of another metadata operation)
*/
void queue_delayed(CDentry *dn);
/**
* Eval strays in the delayed_eval_stray list
*/
void advance_delayed();
/**
* Remote dentry potentially points to a stray. When it is touched,
* call in here to evaluate it for migration (move a stray residing
* on another MDS to this MDS) or reintegration (move a stray dentry's
* inode into a non-stray hardlink dentry and clean up the stray).
*
* @param stray_dn a stray dentry whose inode has been referenced
* by a remote dentry
* @param remote_dn (optional) which remote dentry was touched
* in an operation that led us here: this is used
* as a hint for which remote to reintegrate into
* if there are multiple remotes.
*/
void eval_remote(CDentry *remote_dn);
/**
* Given a dentry within one of my stray directories,
* send it off to a stray directory in another MDS.
*
* This is for use:
* * Case A: when shutting down a rank, we migrate strays
* away from ourselves rather than waiting for purge
* * Case B: when a client request has a trace that refers to
* a stray inode on another MDS, we migrate that inode from
* there to here, in order that we can later re-integrate it
* here.
*
* In case B, the receiver should be calling into eval_stray
* on completion of mv (i.e. inode put), resulting in a subsequent
* reintegration.
*/
void migrate_stray(CDentry *dn, mds_rank_t dest);
/**
* Update stats to reflect a newly created stray dentry. Needed
* because stats on strays live here, but creation happens
* in Server or MDCache. For our purposes "creation" includes
* loading a stray from a dirfrag and migrating a stray from
* another MDS, in addition to creations per-se.
*/
void notify_stray_created();
/**
* Update stats to reflect a removed stray dentry. Needed because
* stats on strays live here, but removal happens in Server or
* MDCache. Also includes migration (rename) of strays from
* this MDS to another MDS.
*/
void notify_stray_removed();
protected:
friend class StrayManagerIOContext;
friend class StrayManagerLogContext;
friend class StrayManagerContext;
friend class C_StraysFetched;
friend class C_RetryEnqueue;
friend class C_PurgeStrayLogged;
friend class C_TruncateStrayLogged;
friend class C_IO_PurgeStrayPurged;
void truncate(CDentry *dn);
/**
* Purge a dentry from a stray directory. This function
* is called once eval_stray is satisfied and StrayManager
* throttling is also satisfied. There is no going back
* at this stage!
*/
void purge(CDentry *dn);
/**
* Completion handler for a Filer::purge on a stray inode.
*/
void _purge_stray_purged(CDentry *dn, bool only_head);
void _purge_stray_logged(CDentry *dn, version_t pdv, MutationRef& mut);
/**
* Callback: we have logged the update to an inode's metadata
* reflecting it's newly-zeroed length.
*/
void _truncate_stray_logged(CDentry *dn, MutationRef &mut);
/**
* Call this on a dentry that has been identified as
* eligible for purging. It will be passed on to PurgeQueue.
*/
void enqueue(CDentry *dn, bool trunc);
/**
* Final part of enqueue() which we may have to retry
* after opening snap parents.
*/
void _enqueue(CDentry *dn, bool trunc);
/**
* When hard links exist to an inode whose primary dentry
* is unlinked, the inode gets a stray primary dentry.
*
* We may later "reintegrate" the inode into a remaining
* non-stray dentry (one of what was previously a remote
* dentry) by issuing a rename from the stray to the other
* dentry.
*/
void reintegrate_stray(CDentry *dn, CDentry *rlink);
/**
* Evaluate a stray dentry for purging or reintegration.
*
* purging: If the inode has no linkage, and no more references, then
* we may decide to purge it.
*
* reintegration: If the inode still has linkage, then it means someone else
* (a hard link) is still referring to it, and we should
* think about reintegrating that inode into the remote dentry.
*
* @returns true if the dentry will be purged (caller should never
* take more refs after this happens), else false.
*/
bool _eval_stray(CDentry *dn);
void _eval_stray_remote(CDentry *stray_dn, CDentry *remote_dn);
// Has passed through eval_stray and still has refs
elist<CDentry*> delayed_eval_stray;
// strays that have been trimmed from cache
std::set<std::string> trimmed_strays;
// Global references for doing I/O
MDSRank *mds;
PerfCounters *logger = nullptr;
bool started = false;
// Stray dentries for this rank (including those not in cache)
uint64_t num_strays = 0;
// Stray dentries
uint64_t num_strays_delayed = 0;
/**
* Entries that have entered enqueue() but not been persistently
* recorded by PurgeQueue yet
*/
uint64_t num_strays_enqueuing = 0;
PurgeQueue &purge_queue;
};
#endif // STRAY_MANAGER_H
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