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https://github.com/RGBCube/serenity
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This is a preparation before we can create a usable mechanism to use filesystem-specific mount flags. To keep some compatibility with userland code, LibC and LibCore mount functions are kept being usable, but now instead of doing an "atomic" syscall, they do multiple syscalls to perform the complete procedure of mounting a filesystem. The FileBackedFileSystem IntrusiveList in the VFS code is now changed to be protected by a Mutex, because when we mount a new filesystem, we need to check if a filesystem is already created for a given source_fd so we do a scan for that OpenFileDescription in that list. If we fail to find an already-created filesystem we create a new one and register it in the list if we successfully mounted it. We use a Mutex because we might need to initiate disk access during the filesystem creation, which will take other mutexes in other parts of the kernel, therefore making it not possible to take a spinlock while doing this.
145 lines
4.2 KiB
C++
145 lines
4.2 KiB
C++
/*
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* Copyright (c) 2020, Sergey Bugaev <bugaevc@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <AK/Atomic.h>
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#include <Kernel/FileSystem/FileBackedFileSystem.h>
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#include <Kernel/FileSystem/Inode.h>
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#include <Kernel/FileSystem/Plan9FS/Definitions.h>
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#include <Kernel/FileSystem/Plan9FS/Message.h>
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#include <Kernel/Library/KBufferBuilder.h>
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namespace Kernel {
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class Plan9FSInode;
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class Plan9FS final : public FileBackedFileSystem {
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friend class Plan9FSInode;
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public:
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virtual ~Plan9FS() override;
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static ErrorOr<NonnullRefPtr<FileSystem>> try_create(OpenFileDescription&, ReadonlyBytes);
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virtual bool supports_watchers() const override { return false; }
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virtual Inode& root_inode() override;
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u16 allocate_tag() { return m_next_tag++; }
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u32 allocate_fid() { return m_next_fid++; }
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enum class ProtocolVersion {
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v9P2000,
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v9P2000u,
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v9P2000L
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};
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private:
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Plan9FS(OpenFileDescription&);
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virtual ErrorOr<void> prepare_to_clear_last_mount() override;
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virtual bool is_initialized_while_locked() override;
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virtual ErrorOr<void> initialize_while_locked() override;
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class Blocker;
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class Plan9FSBlockerSet final : public Thread::BlockerSet {
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public:
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Plan9FSBlockerSet(Plan9FS& fs)
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: m_fs(fs)
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{
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}
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void unblock_completed(u16);
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void unblock_all();
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void try_unblock(Blocker&);
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protected:
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virtual bool should_add_blocker(Thread::Blocker&, void*) override;
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private:
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Plan9FS& m_fs;
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mutable Spinlock<LockRank::None> m_lock {};
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};
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struct ReceiveCompletion final : public AtomicRefCounted<ReceiveCompletion> {
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mutable Spinlock<LockRank::None> lock {};
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bool completed { false };
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const u16 tag;
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OwnPtr<Plan9FSMessage> message;
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ErrorOr<void> result;
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ReceiveCompletion(u16 tag);
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~ReceiveCompletion();
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};
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class Blocker final : public Thread::Blocker {
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public:
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Blocker(Plan9FS& fs, Plan9FSMessage& message, NonnullLockRefPtr<ReceiveCompletion> completion)
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: m_fs(fs)
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, m_message(message)
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, m_completion(move(completion))
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{
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}
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virtual bool setup_blocker() override;
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virtual StringView state_string() const override { return "Waiting"sv; }
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virtual Type blocker_type() const override { return Type::Plan9FS; }
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virtual void will_unblock_immediately_without_blocking(UnblockImmediatelyReason) override;
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NonnullLockRefPtr<ReceiveCompletion> const& completion() const { return m_completion; }
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u16 tag() const { return m_completion->tag; }
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bool is_completed() const;
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bool unblock()
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{
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unblock_from_blocker();
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return true;
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}
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bool unblock(u16 tag);
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private:
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Plan9FS& m_fs;
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Plan9FSMessage& m_message;
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NonnullLockRefPtr<ReceiveCompletion> m_completion;
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bool m_did_unblock { false };
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};
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friend class Blocker;
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virtual StringView class_name() const override { return "Plan9FS"sv; }
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bool is_complete(ReceiveCompletion const&);
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ErrorOr<void> post_message(Plan9FSMessage&, LockRefPtr<ReceiveCompletion>);
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ErrorOr<void> do_read(u8* buffer, size_t);
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ErrorOr<void> read_and_dispatch_one_message();
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ErrorOr<void> post_message_and_wait_for_a_reply(Plan9FSMessage&);
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ErrorOr<void> post_message_and_explicitly_ignore_reply(Plan9FSMessage&);
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ProtocolVersion parse_protocol_version(StringView) const;
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size_t adjust_buffer_size(size_t size) const;
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void thread_main();
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void ensure_thread();
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RefPtr<Plan9FSInode> m_root_inode;
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Atomic<u16> m_next_tag { (u16)-1 };
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Atomic<u32> m_next_fid { 1 };
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ProtocolVersion m_remote_protocol_version { ProtocolVersion::v9P2000 };
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size_t m_max_message_size { 4 * KiB };
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Mutex m_send_lock { "Plan9FS send"sv };
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Plan9FSBlockerSet m_completion_blocker;
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HashMap<u16, NonnullLockRefPtr<ReceiveCompletion>> m_completions;
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Spinlock<LockRank::None> m_thread_lock {};
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RefPtr<Thread> m_thread;
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Atomic<bool> m_thread_running { false };
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Atomic<bool, AK::MemoryOrder::memory_order_relaxed> m_thread_shutdown { false };
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};
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}
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