--- /dev/null
+// 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/elist.h"
+#include <list>
+#include "mds/PurgeQueue.h"
+
+class MDSRank;
+class PerfCounters;
+class CInode;
+class CDentry;
+
+class StrayManager
+{
+ protected:
+ // 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;
+
+ bool started;
+
+ // Stray dentries for this rank (including those not in cache)
+ uint64_t num_strays;
+
+ // Stray dentries
+ uint64_t num_strays_delayed;
+
+ // Entries that have entered enqueue() but not been persistently
+ // recorded by PurgeQueue yet
+ uint64_t num_strays_enqueuing;
+
+ PurgeQueue &purge_queue;
+
+ 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, LogSegment *ls);
+
+ /**
+ * Callback: we have logged the update to an inode's metadata
+ * reflecting it's newly-zeroed length.
+ */
+ void _truncate_stray_logged(CDentry *dn, LogSegment *ls);
+
+ friend class StrayManagerIOContext;
+ friend class StrayManagerLogContext;
+ friend class StrayManagerContext;
+
+ friend class C_StraysFetched;
+ friend class C_OpenSnapParents;
+ friend class C_PurgeStrayLogged;
+ friend class C_TruncateStrayLogged;
+ friend class C_IO_PurgeStrayPurged;
+
+
+ // Call this on a dentry that has been identified as
+ // elegible 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, bool delay=false);
+
+ void _eval_stray_remote(CDentry *stray_dn, CDentry *remote_dn);
+
+ // 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, bool delay=false);
+
+ void set_num_strays(uint64_t num);
+ uint64_t get_num_strays() const { return num_strays; }
+
+ /**
+ * Where eval_stray was previously invoked with delay=true, call
+ * eval_stray again for any dentries that were put on the
+ * delayed_eval_stray list as a result of the original call.
+ *
+ * Used so that various places can call eval_stray(delay=true) during
+ * an operation to identify dentries of interest, and then call
+ * this function later during trim in order to do the final
+ * evaluation (and resulting actions) while not in the middle of another
+ * metadata operation.
+ */
+ 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();
+};
+
+#endif // STRAY_MANAGER_H
Code Review / stor4nfv.git / blobdiff