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https://github.com/RGBCube/serenity
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df66c28479
These APIs were clearly modeled after Ext2FS internals, and make perfect sense
in Ext2FS context. The new APIs are more generic, and map better to the
semantics exported to the userspace, where inode identifiers only appear in
stat() and readdir() output, but never in any input.
This will also hopefully reduce the potential for races (see commit c44b4d61f3).
Lastly, this makes it way more viable to implement a filesystem that only
synthesizes its inodes lazily when queried, and destroys them when they are no
longer in use. With inode identifiers being used to reference inodes, the only
choice for such a filesystem is to persist any inode it has given out the
identifier for, because it might be queried at any later time. With direct
references to inodes, the filesystem will know when the last reference is
dropped and the inode can be safely destroyed.
121 lines
3.7 KiB
C++
121 lines
3.7 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include <AK/RefCounted.h>
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#include <AK/RefPtr.h>
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#include <AK/String.h>
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#include <Kernel/FileSystem/InodeIdentifier.h>
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#include <Kernel/KResult.h>
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#include <Kernel/Lock.h>
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#include <Kernel/UnixTypes.h>
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namespace Kernel {
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static const u32 mepoch = 476763780;
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class Inode;
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class FileDescription;
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class LocalSocket;
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class VMObject;
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class FS : public RefCounted<FS> {
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friend class Inode;
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public:
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virtual ~FS();
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unsigned fsid() const { return m_fsid; }
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static FS* from_fsid(u32);
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static void sync();
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static void lock_all();
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virtual bool initialize() = 0;
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virtual const char* class_name() const = 0;
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virtual NonnullRefPtr<Inode> root_inode() const = 0;
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virtual bool supports_watchers() const { return false; }
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bool is_readonly() const { return m_readonly; }
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virtual unsigned total_block_count() const { return 0; }
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virtual unsigned free_block_count() const { return 0; }
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virtual unsigned total_inode_count() const { return 0; }
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virtual unsigned free_inode_count() const { return 0; }
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virtual KResult prepare_to_unmount() const { return KSuccess; }
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// FIXME: This data structure is very clunky and unpleasant. Replace it with something nicer.
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struct DirectoryEntry {
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DirectoryEntry(const char* name, InodeIdentifier, u8 file_type);
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DirectoryEntry(const char* name, size_t name_length, InodeIdentifier, u8 file_type);
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char name[256];
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size_t name_length { 0 };
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InodeIdentifier inode;
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u8 file_type { 0 };
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};
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virtual RefPtr<Inode> get_inode(InodeIdentifier) const = 0;
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virtual void flush_writes() { }
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size_t block_size() const { return m_block_size; }
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virtual bool is_file_backed() const { return false; }
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protected:
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FS();
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void set_block_size(size_t);
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mutable Lock m_lock { "FS" };
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private:
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unsigned m_fsid { 0 };
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size_t m_block_size { 0 };
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bool m_readonly { false };
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};
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inline FS* InodeIdentifier::fs()
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{
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return FS::from_fsid(m_fsid);
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}
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inline const FS* InodeIdentifier::fs() const
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{
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return FS::from_fsid(m_fsid);
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}
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}
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namespace AK {
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template<>
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struct Traits<Kernel::InodeIdentifier> : public GenericTraits<Kernel::InodeIdentifier> {
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static unsigned hash(const Kernel::InodeIdentifier& inode) { return pair_int_hash(inode.fsid(), inode.index()); }
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};
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}
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