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e0d0c0fae0
Summary:
In preparation for `LMDBFileContentStore`, this diff extends the OverlayFile class to hold either a `folly::File` or an `InodeNumber`.
`FsFileContentStore` returns a `folly::File` which wraps an open `fd` to the raw file on disk. This allows for direct manipulation of the data without a trip through the `FsFileContentStore`. It also acts as a way to refcount any open IO requests to the underlying overlay storage (see: D17973664)
`LMDBFileContentStore` doesn't have the ability to return a file descriptor for direct manipulation, so instead it will return its key and operations to the `OverlayFile` will query `LMDBFileContentStore` on demand using the given `InodeNumber`.
In theory, `LMDBFileContentStore` doesn't need the concept of an `OverlayFile` since it doesn't need to refcount open file handles, but adapting the class to work with the `LMDBFileContentStore` model is cleaner than working around `OverlayFile`/`OverlayFileAccess` class.
The following images depict the two different architectures
{F1075774500}
{F1075774523}
Reviewed By: kmancini
Differential Revision: D48569910
fbshipit-source-id: 2f171ede0c4ac168ca01bb1c65dc9d401edc4681
71 lines
2.1 KiB
C++
71 lines
2.1 KiB
C++
/*
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* Copyright (c) Meta Platforms, Inc. and affiliates.
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*
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* This software may be used and distributed according to the terms of the
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* GNU General Public License version 2.
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*/
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#pragma once
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#include <folly/Expected.h>
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#include <folly/File.h>
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#include <folly/portability/SysUio.h>
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#include <variant>
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#include "eden/common/utils/FileOffset.h"
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#include "eden/fs/inodes/InodeNumber.h"
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namespace folly {
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class File;
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}
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namespace facebook::eden {
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class Overlay;
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/**
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* Class to manage IO reference counting for an Overlay to support closing the
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* Overlay class even if it is still in use.
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*
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* If an OverlayFile was created from a folly::File, this class will manage
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* reference counting for the underlying on-disk Overlay storage.
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*/
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class OverlayFile {
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public:
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OverlayFile() = default;
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explicit OverlayFile(folly::File file, std::weak_ptr<Overlay> overlay);
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explicit OverlayFile(InodeNumber ino, std::weak_ptr<Overlay> overlay);
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explicit OverlayFile(
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std::variant<folly::File, InodeNumber> data,
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std::weak_ptr<Overlay> overlay);
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OverlayFile(OverlayFile&&) = default;
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OverlayFile& operator=(OverlayFile&&) = default;
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folly::Expected<struct stat, int> fstat() const;
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folly::Expected<ssize_t, int>
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preadNoInt(void* buf, size_t n, FileOffset offset) const;
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folly::Expected<FileOffset, int> lseek(FileOffset offset, int whence) const;
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folly::Expected<ssize_t, int>
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pwritev(const iovec* iov, int iovcnt, FileOffset offset) const;
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folly::Expected<int, int> ftruncate(FileOffset length) const;
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folly::Expected<int, int> fsync() const;
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folly::Expected<int, int> fallocate(FileOffset offset, FileOffset length)
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const;
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folly::Expected<int, int> fdatasync() const;
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folly::Expected<std::string, int> readFile() const;
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private:
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OverlayFile(const OverlayFile&) = delete;
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OverlayFile& operator=(const OverlayFile&) = delete;
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/**
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* This will contain a folly::File if created from an Overlay with type
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* InodeCatalogType::Legacy or an InodeNumber if created from an Overlay with
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* type InodeCatalogType::LMDB
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*/
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std::variant<folly::File, InodeNumber> data_;
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std::weak_ptr<Overlay> overlay_;
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};
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} // namespace facebook::eden
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