sapling/eden/fuse/FileInode.h
Wez Furlong 174d0b9b0a eden: assign our own file handle numbers and track all file handles
Summary:
Previously we would simply report the raw pointer address to the kernel and
rely on it to return that same number to us as the file handle, and make sure
that it told us to shut down the handle when it was closed.

This meant that we had no real idea about which files were still open.

For our future live upgrade plans we need to be able to know this so that we
can transfer the appropriate information to our replacement process.

To facilitate this this diff implements a FileHandleMap class that will assign
file handle numbers and keep track of the instances.  The number assignment
strategy is the same as it used to be in the common case: we take the address
of the newly created instance and use that 64-bit number as the file handle
number.  However, in the future when we transfer the mapping to a new process,
we may experience a collision when subsequently opening a file handle.  To deal
with that, we have a bounded number of attempts to assign a random file handle
number.

We don't yet offer a means to iterate the map, but it would be trivial to
expose such an accessor when we're ready to use it.

Since we now keep track of these things via shared_ptr this changes the
appropriate portions of the fuse interface from unique_ptr to shared_ptr.

Reviewed By: simpkins

Differential Revision: D3602364

fbshipit-source-id: dd996339c2838225a2caeee9da16ef99a06c1e2b
2016-07-26 10:00:11 -07:00

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/*
* Copyright (c) 2016, 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 "InodeBase.h"
namespace facebook {
namespace eden {
namespace fusell {
class FileInode : public InodeBase {
public:
explicit FileInode(fuse_ino_t ino);
// See Dispatcher::readlink
virtual folly::Future<std::string> readlink();
virtual folly::Future<std::shared_ptr<FileHandle>> open(
const struct fuse_file_info& fi);
virtual folly::Future<uint64_t> bmap(size_t blocksize, uint64_t idx);
};
}
}
}