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diff --git a/src/mds/ScrubStack.h b/src/mds/ScrubStack.h
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+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+/*
+ * Ceph - scalable distributed file system
+ *
+ * Copyright (C) 2014 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 SCRUBSTACK_H_
+#define SCRUBSTACK_H_
+
+#include "CDir.h"
+#include "CDentry.h"
+#include "CInode.h"
+#include "MDSContext.h"
+#include "ScrubHeader.h"
+
+#include "common/LogClient.h"
+#include "include/elist.h"
+#include "messages/MMDSScrub.h"
+#include "messages/MMDSScrubStats.h"
+
+class MDCache;
+class Finisher;
+
+class ScrubStack {
+public:
+  ScrubStack(MDCache *mdc, LogChannelRef &clog, Finisher *finisher_) :
+    mdcache(mdc),
+    clog(clog),
+    finisher(finisher_),
+    scrub_stack(member_offset(MDSCacheObject, item_scrub)),
+    scrub_waiting(member_offset(MDSCacheObject, item_scrub)) {}
+  ~ScrubStack() {
+    ceph_assert(scrub_stack.empty());
+    ceph_assert(!scrubs_in_progress);
+  }
+  /**
+   * Put the inode at either the top or bottom of the stack, with the
+   * given scrub params, and kick off more scrubbing.
+   * @param in The inode to scrub
+   * @param header The ScrubHeader propagated from wherever this scrub
+   */
+  int enqueue(CInode *in, ScrubHeaderRef& header, bool top);
+  /**
+   * Abort an ongoing scrub operation. The abort operation could be
+   * delayed if there are in-progress scrub operations on going. The
+   * caller should provide a context which is completed after all
+   * in-progress scrub operations are completed and pending inodes
+   * are removed from the scrub stack (with the context callbacks for
+   * inodes completed with -CEPHFS_ECANCELED).
+   * @param on_finish Context callback to invoke after abort
+   */
+  void scrub_abort(Context *on_finish);
+
+  /**
+   * Pause scrub operations. Similar to abort, pause is delayed if
+   * there are in-progress scrub operations on going. The caller
+   * should provide a context which is completed after all in-progress
+   * scrub operations are completed. Subsequent scrub operations are
+   * queued until scrub is resumed.
+   * @param on_finish Context callback to invoke after pause
+   */
+  void scrub_pause(Context *on_finish);
+
+  /**
+   * Resume a paused scrub. Unlike abort or pause, this is instantaneous.
+   * Pending pause operations are cancelled (context callbacks are
+   * invoked with -CEPHFS_ECANCELED).
+   * @returns 0 (success) if resumed, -CEPHFS_EINVAL if an abort is in-progress.
+   */
+  bool scrub_resume();
+
+  /**
+   * Get the current scrub status as human readable string. Some basic
+   * information is returned such as number of inodes pending abort/pause.
+   */
+  void scrub_status(Formatter *f);
+
+  /**
+   * Get a high level scrub status summary such as current scrub state
+   * and scrub paths.
+   */
+  std::string_view scrub_summary();
+
+  static bool is_idle(std::string_view state_str) {
+    return state_str == "idle";
+  }
+
+  bool is_scrubbing() const { return !scrub_stack.empty(); }
+
+  void advance_scrub_status();
+
+  void handle_mds_failure(mds_rank_t mds);
+
+  void dispatch(const cref_t<Message> &m);
+
+  MDCache *mdcache;
+
+protected:
+
+  // reference to global cluster log client
+  LogChannelRef &clog;
+
+  /// A finisher needed so that we don't re-enter kick_off_scrubs
+  Finisher *finisher;
+
+  /// The stack of inodes we want to scrub
+  elist<MDSCacheObject*> scrub_stack;
+  elist<MDSCacheObject*> scrub_waiting;
+  /// current number of dentries we're actually scrubbing
+  int scrubs_in_progress = 0;
+  int stack_size = 0;
+
+  struct scrub_remote_t {
+    std::string tag;
+    std::set<mds_rank_t> gather_set;
+  };
+  std::map<CInode*, scrub_remote_t> remote_scrubs;
+
+  unsigned scrub_epoch = 2;
+  unsigned scrub_epoch_fully_acked = 0;
+  unsigned scrub_epoch_last_abort = 2;
+  // check if any mds is aborting scrub after mds.0 starts
+  bool scrub_any_peer_aborting = true;
+
+  struct scrub_stat_t {
+    unsigned epoch_acked = 0;
+    std::set<std::string> scrubbing_tags;
+    bool aborting = false;
+  };
+  std::vector<scrub_stat_t> mds_scrub_stats;
+
+  std::map<std::string, ScrubHeaderRef> scrubbing_map;
+
+  friend class C_RetryScrub;
+private:
+  // scrub abort is _not_ a state, rather it's an operation that's
+  // performed after in-progress scrubs are finished.
+  enum State {
+    STATE_RUNNING = 0,
+    STATE_IDLE,
+    STATE_PAUSING,
+    STATE_PAUSED,
+  };
+  friend std::ostream &operator<<(std::ostream &os, const State &state);
+
+  friend class C_InodeValidated;
+
+  int _enqueue(MDSCacheObject *obj, ScrubHeaderRef& header, bool top);
+  /**
+   * Remove the inode/dirfrag from the stack.
+   */
+  inline void dequeue(MDSCacheObject *obj);
+
+  /**
+   * Kick off as many scrubs as are appropriate, based on the current
+   * state of the stack.
+   */
+  void kick_off_scrubs();
+
+  /**
+   * Move the inode/dirfrag that can't be scrubbed immediately
+   * from scrub queue to waiting list.
+   */
+  void add_to_waiting(MDSCacheObject *obj);
+  /**
+   * Move the inode/dirfrag back to scrub queue.
+   */
+  void remove_from_waiting(MDSCacheObject *obj, bool kick=true);
+  /**
+   * Validate authority of the inode. If current mds is not auth of the inode,
+   * forword scrub to auth mds.
+   */
+  bool validate_inode_auth(CInode *in);
+
+  /**
+   * Scrub a file inode.
+   * @param in The inode to scrub
+   */
+  void scrub_file_inode(CInode *in);
+
+  /**
+   * Callback from completion of CInode::validate_disk_state
+   * @param in The inode we were validating
+   * @param r The return status from validate_disk_state
+   * @param result Populated results from validate_disk_state
+   */
+  void _validate_inode_done(CInode *in, int r,
+			    const CInode::validated_data &result);
+
+  /**
+   * Scrub a directory inode. It queues child dirfrags, then does
+   * final scrub of the inode.
+   *
+   * @param in The directory indoe to scrub
+   * @param added_children set to true if we pushed some of our children
+   * @param done set to true if we started to do final scrub
+   */
+  void scrub_dir_inode(CInode *in, bool *added_children, bool *done);
+  /**
+   * Scrub a dirfrag. It queues child dentries, then does final
+   * scrub of the dirfrag.
+   *
+   * @param dir The dirfrag to scrub (must be auth)
+   * @param done set to true if we started to do final scrub
+   */
+  void scrub_dirfrag(CDir *dir, bool *done);
+  /**
+   * Scrub a directory-representing dentry.
+   *
+   * @param in The directory inode we're doing final scrub on.
+   */
+  void scrub_dir_inode_final(CInode *in);
+  /**
+   * Set scrub state
+   * @param next_state State to move the scrub to.
+   */
+  void set_state(State next_state);
+
+  /**
+   * Is scrub in one of transition states (running, pausing)
+   */
+  bool scrub_in_transition_state();
+
+  /**
+   * complete queued up contexts
+   * @param r return value to complete contexts.
+   */
+  void complete_control_contexts(int r);
+
+  /**
+   * ask peer mds (rank > 0) to abort/pause/resume scrubs
+   */
+  void send_state_message(int op);
+
+  /**
+   * Abort pending scrubs for inodes waiting in the inode stack.
+   * Completion context is complete with -CEPHFS_ECANCELED.
+   */
+  void abort_pending_scrubs();
+
+  /**
+   * Return path for a given inode.
+   * @param in inode to make path entry.
+   */
+  std::string scrub_inode_path(CInode *in) {
+    std::string path;
+    in->make_path_string(path, true);
+    return (path.empty() ? "/" : path.c_str());
+  }
+
+  /**
+   * Send scrub information (queued/finished scrub path and summary)
+   * to cluster log.
+   * @param in inode for which scrub has been queued or finished.
+   */
+  void clog_scrub_summary(CInode *in=nullptr);
+
+  void handle_scrub(const cref_t<MMDSScrub> &m);
+  void handle_scrub_stats(const cref_t<MMDSScrubStats> &m);
+
+  State state = STATE_IDLE;
+  bool clear_stack = false;
+
+  // list of pending context completions for asynchronous scrub
+  // control operations.
+  std::vector<Context *> control_ctxs;
+};
+
+#endif /* SCRUBSTACK_H_ */