Revert "Kernel/Storage: Remove the ramdisk implementation"

This reverts commit 4e0f85432a as the
ramdisk code is useful for the bring-up of the aarch64 port. Once the
kernel supports better ram-based filesystems, this code will be removed
again.

Kernel/Storage/Ramdisk/Controller.cpp

@@ -0,0 +1,67 @@
+/*
+ * Copyright (c) 2021, the SerenityOS developers.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/OwnPtr.h>
+#include <AK/Types.h>
+#include <Kernel/Library/LockRefPtr.h>
+#include <Kernel/Storage/Ramdisk/Controller.h>
+
+namespace Kernel {
+
+NonnullLockRefPtr<RamdiskController> RamdiskController::initialize()
+{
+    return adopt_lock_ref(*new RamdiskController());
+}
+
+bool RamdiskController::reset()
+{
+    TODO();
+}
+
+bool RamdiskController::shutdown()
+{
+    TODO();
+}
+
+size_t RamdiskController::devices_count() const
+{
+    return m_devices.size();
+}
+
+void RamdiskController::complete_current_request(AsyncDeviceRequest::RequestResult)
+{
+    VERIFY_NOT_REACHED();
+}
+
+RamdiskController::RamdiskController()
+    : StorageController(0)
+{
+    // Populate ramdisk controllers from Multiboot boot modules, if any.
+    size_t count = 0;
+    MM.for_each_used_memory_range([&](auto& used_memory_range) {
+        if (used_memory_range.type == Memory::UsedMemoryRangeType::BootModule) {
+            size_t length = Memory::page_round_up(used_memory_range.end.get()).release_value_but_fixme_should_propagate_errors() - used_memory_range.start.get();
+            auto region_or_error = MM.allocate_kernel_region(used_memory_range.start, length, "Ramdisk"sv, Memory::Region::Access::ReadWrite);
+            if (region_or_error.is_error()) {
+                dmesgln("RamdiskController: Failed to allocate kernel region of size {}", length);
+            } else {
+                m_devices.append(RamdiskDevice::create(*this, region_or_error.release_value(), 6, count));
+            }
+            count++;
+        }
+    });
+}
+
+RamdiskController::~RamdiskController() = default;
+
+LockRefPtr<StorageDevice> RamdiskController::device(u32 index) const
+{
+    if (index >= m_devices.size())
+        return nullptr;
+    return m_devices[index];
+}
+
+}

Kernel/Storage/Ramdisk/Controller.h

@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2021, the SerenityOS developers.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/OwnPtr.h>
+#include <AK/Types.h>
+#include <Kernel/Library/LockRefPtr.h>
+#include <Kernel/Storage/Ramdisk/Device.h>
+#include <Kernel/Storage/StorageController.h>
+#include <Kernel/Storage/StorageDevice.h>
+
+namespace Kernel {
+
+class AsyncBlockDeviceRequest;
+
+class RamdiskController final : public StorageController {
+public:
+    static NonnullLockRefPtr<RamdiskController> initialize();
+    virtual ~RamdiskController() override;
+
+    virtual LockRefPtr<StorageDevice> device(u32 index) const override;
+    virtual bool reset() override;
+    virtual bool shutdown() override;
+    virtual size_t devices_count() const override;
+    virtual void complete_current_request(AsyncDeviceRequest::RequestResult) override;
+
+private:
+    RamdiskController();
+
+    NonnullLockRefPtrVector<RamdiskDevice> m_devices;
+};
+}

Kernel/Storage/Ramdisk/Device.cpp

@@ -0,0 +1,60 @@
+/*
+ * Copyright (c) 2021, the SerenityOS developers.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/Memory.h>
+#include <AK/StringView.h>
+#include <Kernel/Devices/DeviceManagement.h>
+#include <Kernel/FileSystem/OpenFileDescription.h>
+#include <Kernel/Storage/Ramdisk/Controller.h>
+#include <Kernel/Storage/Ramdisk/Device.h>
+
+namespace Kernel {
+
+NonnullLockRefPtr<RamdiskDevice> RamdiskDevice::create(RamdiskController const& controller, NonnullOwnPtr<Memory::Region>&& region, int major, int minor)
+{
+    auto device_or_error = DeviceManagement::try_create_device<RamdiskDevice>(controller, move(region), major, minor);
+    // FIXME: Find a way to propagate errors
+    VERIFY(!device_or_error.is_error());
+    return device_or_error.release_value();
+}
+
+RamdiskDevice::RamdiskDevice(RamdiskController const& controller, NonnullOwnPtr<Memory::Region>&& region, int major, int minor)
+    : StorageDevice({}, LUNAddress { controller.controller_id(), 0, 0 }, 0, major, minor, 512, region->size() / 512)
+    , m_region(move(region))
+{
+    dmesgln("Ramdisk: Device #{} @ {}, Capacity={}", minor, m_region->vaddr(), max_addressable_block() * 512);
+}
+
+RamdiskDevice::~RamdiskDevice() = default;
+
+StringView RamdiskDevice::class_name() const
+{
+    return "RamdiskDevice"sv;
+}
+
+void RamdiskDevice::start_request(AsyncBlockDeviceRequest& request)
+{
+    MutexLocker locker(m_lock);
+
+    u8* base = m_region->vaddr().as_ptr();
+    size_t size = m_region->size();
+    u8* offset = base + request.block_index() * request.block_size();
+    size_t length = request.buffer_size();
+
+    if ((offset + length > base + size) || (offset + length < base)) {
+        request.complete(AsyncDeviceRequest::Failure);
+    } else {
+        ErrorOr<void> result;
+        if (request.request_type() == AsyncBlockDeviceRequest::Read) {
+            result = request.buffer().write(offset, length);
+        } else {
+            result = request.buffer().read(offset, length);
+        }
+        request.complete(!result.is_error() ? AsyncDeviceRequest::Success : AsyncDeviceRequest::MemoryFault);
+    }
+}
+
+}

Kernel/Storage/Ramdisk/Device.h

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2021, the SerenityOS developers.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <Kernel/Locking/Mutex.h>
+#include <Kernel/Storage/StorageDevice.h>
+
+namespace Kernel {
+
+class RamdiskController;
+
+class RamdiskDevice final : public StorageDevice {
+    friend class RamdiskController;
+    friend class DeviceManagement;
+
+public:
+    static NonnullLockRefPtr<RamdiskDevice> create(RamdiskController const&, NonnullOwnPtr<Memory::Region>&& region, int major, int minor);
+    virtual ~RamdiskDevice() override;
+
+    // ^DiskDevice
+    virtual StringView class_name() const override;
+
+private:
+    RamdiskDevice(RamdiskController const&, NonnullOwnPtr<Memory::Region>&&, int major, int minor);
+
+    // ^BlockDevice
+    virtual void start_request(AsyncBlockDeviceRequest&) override;
+
+    // ^StorageDevice
+    virtual CommandSet command_set() const override { return CommandSet::PlainMemory; }
+
+    Mutex m_lock { "RamdiskDevice"sv };
+
+    NonnullOwnPtr<Memory::Region> m_region;
+};
+
+}