sapling/eden/fs/inodes/TreeInode.h

/*
 *  Copyright (c) 2016-present, Facebook, Inc.
 *  All rights reserved.
 *
 *  This source code is licensed under the BSD-style license found in the
 *  LICENSE file in the root directory of this source tree. An additional grant
 *  of patent rights can be found in the PATENTS file in the same directory.
 *
 */
#pragma once
#include <folly/Optional.h>
#include "eden/fs/inodes/InodeBase.h"
#include "eden/fs/model/Hash.h"
#include "eden/utils/PathMap.h"

namespace facebook {
namespace eden {

class EdenMount;
class FileHandle;
class InodeMap;
class ObjectStore;
class Overlay;
class RenameLock;
class Tree;

// Represents a Tree instance in a form that FUSE can consume
class TreeInode : public InodeBase {
 public:
  /** Represents a directory entry.
   * A directory entry holds the combined Tree and Overlay data;
   * if a directory is only partially materialized the entire
   * directory contents be part of this data, but the individual
   * entries will indicate whether they have been materialized or not.
   */
  struct Entry {
    /** The complete st_mode value for this entry */
    mode_t mode;
    /** If !materialized, the blob or tree hash for this entry in
     * the local store */
    folly::Optional<Hash> hash;
    /** true if the entry has been materialized to the overlay.
     * For a directory this means that the directory exists, for
     * a file it means that the file exists */
    bool materialized{false};

    /**
     * A pointer to the child inode, if it is loaded, or null if it is not
     * loaded.
     *
     * Note that we store this as a raw pointer.  Children inodes hold a
     * reference to their parent TreeInode, not the other way around.
     * Children inodes can be destroyed only in one of two ways:
     * - Being unlinked, then having their last reference go away.
     *   In this case they will be removed from our entries list when they are
     *   unlinked.
     * - Being unloaded (after their reference count is already 0).  In this
     *   case the parent TreeInodes responsible for triggering unloading of its
     *   children, so it resets this pointer to null when it unloads the child.
     *
     * TODO: This should perhaps be a folly::Variant with the above data.
     * If the child is loaded, it should be the source of truth about all of
     * the data for the child.
     */
    InodeBase* inode{nullptr};
  };

  /** Represents a directory in the overlay */
  struct Dir {
    /** The direct children of this directory */
    PathMap<std::unique_ptr<Entry>> entries;
    /** If the origin of this dir was a Tree, the hash of that tree */
    folly::Optional<Hash> treeHash;

    /** true if the dir has been materialized to the overlay.
     * If the contents match the original tree, this is false. */
    bool materialized{false};
  };

  /** Holds the results of a create operation.
   *
   * It is important that the file handle creation respect O_EXCL if
   * it set in the flags parameter to TreeInode::create.
   */
  struct CreateResult {
    /// file attributes and cache ttls.
    fusell::Dispatcher::Attr attr;
    /// The newly created inode instance.
    InodePtr inode;
    /// The newly opened file handle.
    std::shared_ptr<FileHandle> file;

    explicit CreateResult(const fusell::MountPoint* mount) : attr(mount) {}
  };

  TreeInode(
      fuse_ino_t ino,
      TreeInodePtr parent,
      PathComponentPiece name,
      Entry* entry,
      std::unique_ptr<Tree>&& tree);

  /// Construct an inode that only has backing in the Overlay area
  TreeInode(
      fuse_ino_t ino,
      TreeInodePtr parent,
      PathComponentPiece name,
      Entry* entry,
      Dir&& dir);

  /// Constructors for the root TreeInode
  TreeInode(EdenMount* mount, std::unique_ptr<Tree>&& tree);
  TreeInode(EdenMount* mount, Dir&& tree);

  ~TreeInode();

  folly::Future<fusell::Dispatcher::Attr> getattr() override;
  fusell::Dispatcher::Attr getAttrLocked(const Dir* contents);

  /** Implements the InodeBase method used by the Dispatcher
   * to create the Inode instance for a given name */
  folly::Future<InodePtr> getChildByName(PathComponentPiece namepiece);

  /**
   * Get the inode object for a child of this directory.
   *
   * The Inode object will be loaded if it is not already loaded.
   */
  folly::Future<InodePtr> getOrLoadChild(PathComponentPiece name);
  folly::Future<TreeInodePtr> getOrLoadChildTree(PathComponentPiece name);

  /**
   * Recursively look up a child inode.
   *
   * The Inode object in question, and all intervening TreeInode objects,
   * will be loaded if they are not already loaded.
   */
  folly::Future<InodePtr> getChildRecursive(RelativePathPiece name);

  fuse_ino_t getChildInodeNumber(PathComponentPiece name);

  folly::Future<std::shared_ptr<fusell::DirHandle>> opendir(
      const struct fuse_file_info& fi);
  folly::Future<folly::Unit> rename(
      PathComponentPiece name,
      TreeInodePtr newParent,
      PathComponentPiece newName);

  std::unique_ptr<InodeBase> renameHelper(
      Dir* sourceContents,
      PathComponentPiece sourceName,
      TreeInodePtr destParent,
      Dir* destContents,
      PathComponentPiece destName,
      const RenameLock& renameLock);

  fuse_ino_t getInode() const;

  const folly::Synchronized<Dir>& getContents() const {
    return contents_;
  }
  folly::Synchronized<Dir>& getContents() {
    return contents_;
  }

  /**
   * Get the InodeMap for this tree's EdenMount.
   *
   * The InodeMap is guaranteed to remain valid for at least the lifetime of
   * the TreeInode object.
   */
  InodeMap* getInodeMap() const;

  /**
   * Get the ObjectStore for this mount point.
   *
   * The ObjectStore is guaranteed to remain valid for at least the lifetime of
   * the TreeInode object.  (The ObjectStore is owned by the EdenMount.)
   */
  ObjectStore* getStore() const;

  const std::shared_ptr<Overlay>& getOverlay() const;
  folly::Future<CreateResult>
  create(PathComponentPiece name, mode_t mode, int flags);
  folly::Future<fuse_entry_param> symlink(
      PathComponentPiece name,
      folly::StringPiece contents);

  TreeInodePtr mkdir(PathComponentPiece name, mode_t mode);
  folly::Future<folly::Unit> unlink(PathComponentPiece name);
  folly::Future<folly::Unit> rmdir(PathComponentPiece name);

  /** Called in a thrift context to switch the active snapshot.
   * Since this is called in a thrift context, RequestData::get() won't
   * return the usual results and the appropriate information must
   * be passed down from the thrift server itself.
   */
  void performCheckout(const Hash& hash);

  /** Ensure that the overlay is tracking metadata for this inode
   * This is required whenever we are about to make a structural change
   * in the tree; renames, creation, deletion. */
  void materializeDirAndParents();

  /**
   * Internal API only for use by InodeMap.
   *
   * InodeMap will call this API when a child inode needs to be loaded.
   * The TreeInode will call InodeMap::inodeLoadComplete() or
   * InodeMap::inodeLoadFailed() when the load finishes.
   */
  void loadChildInode(PathComponentPiece name, fuse_ino_t number);

  /**
   * Unload all unreferenced children under this tree (recursively).
   *
   * This walks the children underneath this tree, unloading any inodes that
   * are unreferenced.
   */
  void unloadChildrenNow();

 private:
  void registerInodeLoadComplete(
      folly::Future<InodePtr>& future,
      PathComponentPiece name,
      fuse_ino_t number);

  folly::Future<InodePtr> startLoadingInodeNoThrow(
      Entry* entry,
      PathComponentPiece name,
      fuse_ino_t number) noexcept;

  folly::Future<InodePtr>
  startLoadingInode(Entry* entry, PathComponentPiece name, fuse_ino_t number);

  /** Translates a Tree object from our store into a Dir object
   * used to track the directory in the inode */
  static Dir buildDirFromTree(const Tree* tree);

  /**
   * Get a TreeInodePtr to ourself.
   *
   * This uses TreeInodePtr::newPtrFromExisting() internally.
   *
   * This should only be called in contexts where we know an external caller
   * already has an existing reference to us.  (Which is most places--a caller
   * has to have a reference to us in order to call any of our APIs.)
   */
  TreeInodePtr inodePtrFromThis() {
    return TreeInodePtr::newPtrFromExisting(this);
  }

  folly::Future<folly::Unit>
  rmdirImpl(PathComponent name, TreeInodePtr child, unsigned int attemptNum);

  folly::Synchronized<Dir> contents_;
  /** Can be nullptr for the root inode only, otherwise will be non-null */
  TreeInode::Entry* entry_{nullptr};
};
}
}