Kernel/Storage: Add LUN address to each StorageDevice

LUN address is essentially how people used to address SCSI devices back
in the day we had these devices more in use. However, SCSI was taken as
an abstraction layer for many Unix and Unix-like systems, so it still
common to see LUN addresses in use. In Serenity, we don't really provide
such abstraction layer, and therefore until now, we didn't use LUNs too.
However (again), this changes, as we want to let users to address their
devices under SysFS easily. LUNs make sense in that regard, because they
can be easily adapted to different interfaces besides SCSI.
For example, for legacy ATA hard drive being connected to the first IDE
controller which was enumerated on the PCI bus, and then to the primary
channel as slave device, the LUN address would be 0:0:1.

To make this happen, we add unique ID number to each StorageController,
which increments by 1 for each new instance of StorageController. Then,
we adapt the ATA and NVMe devices to use these numbers and generate LUN
in the construction time.

Kernel/CMakeLists.txt

@@ -116,6 +116,7 @@ set(KERNEL_SOURCES
     Storage/NVMe/NVMeQueue.cpp
     Storage/Ramdisk/Controller.cpp
     Storage/Ramdisk/Device.cpp
+    Storage/StorageController.cpp
     Storage/StorageDevice.cpp
     Storage/StorageManagement.cpp
     DoubleBuffer.cpp

Kernel/Storage/ATA/ATADevice.cpp

@@ -13,8 +13,13 @@
 
 namespace Kernel {
 
+static StorageDevice::LUNAddress convert_ata_address_to_lun_address(ATAController const& controller, ATADevice::Address ata_address)
+{
+    return StorageDevice::LUNAddress { controller.controller_id(), ata_address.port, ata_address.subport };
+}
+
 ATADevice::ATADevice(ATAController const& controller, ATADevice::Address ata_address, MinorNumber minor_number, u16 capabilities, u16 logical_sector_size, u64 max_addressable_block, NonnullOwnPtr<KString> early_storage_name)
-    : StorageDevice(StorageManagement::storage_type_major_number(), minor_number, logical_sector_size, max_addressable_block, move(early_storage_name))
+    : StorageDevice(convert_ata_address_to_lun_address(controller, ata_address), StorageManagement::storage_type_major_number(), minor_number, logical_sector_size, max_addressable_block, move(early_storage_name))
     , m_controller(controller)
     , m_ata_address(ata_address)
     , m_capabilities(capabilities)

Kernel/Storage/NVMe/NVMeController.cpp

@@ -19,13 +19,13 @@
 #include <Kernel/Sections.h>
 
 namespace Kernel {
-Atomic<u8> NVMeController::controller_id {};
+Atomic<u8> NVMeController::s_controller_id {};
 
 UNMAP_AFTER_INIT ErrorOr<NonnullRefPtr<NVMeController>> NVMeController::try_initialize(Kernel::PCI::DeviceIdentifier const& device_identifier, bool is_queue_polled)
 {
     auto controller = TRY(adopt_nonnull_ref_or_enomem(new NVMeController(device_identifier)));
     TRY(controller->initialize(is_queue_polled));
-    NVMeController::controller_id++;
+    NVMeController::s_controller_id++;
     return controller;
 }
 
@@ -207,7 +207,7 @@ UNMAP_AFTER_INIT ErrorOr<void> NVMeController::identify_and_init_namespaces()
 
             dbgln_if(NVME_DEBUG, "NVMe: Block count is {} and Block size is {}", block_counts, block_size);
 
-            m_namespaces.append(TRY(NVMeNameSpace::try_create(m_queues, controller_id.load(), nsid, block_counts, block_size)));
+            m_namespaces.append(TRY(NVMeNameSpace::try_create(*this, m_queues, s_controller_id.load(), nsid, block_counts, block_size)));
             m_device_count++;
             dbgln_if(NVME_DEBUG, "NVMe: Initialized namespace with NSID: {}", nsid);
         }

Kernel/Storage/NVMe/NVMeController.h

@@ -77,6 +77,6 @@ private:
     AK::Time m_ready_timeout;
     u32 m_bar { 0 };
     u8 m_dbl_stride { 0 };
-    static Atomic<u8> controller_id;
+    static Atomic<u8> s_controller_id;
 };
 }

Kernel/Storage/NVMe/NVMeNameSpace.cpp

@@ -7,21 +7,22 @@
 #include "NVMeNameSpace.h"
 #include <AK/NonnullOwnPtr.h>
 #include <Kernel/Devices/DeviceManagement.h>
+#include <Kernel/Storage/NVMe/NVMeController.h>
 #include <Kernel/Storage/StorageManagement.h>
 
 namespace Kernel {
 
-UNMAP_AFTER_INIT ErrorOr<NonnullRefPtr<NVMeNameSpace>> NVMeNameSpace::try_create(NonnullRefPtrVector<NVMeQueue> queues, u8 controller_id, u16 nsid, size_t storage_size, size_t lba_size)
+UNMAP_AFTER_INIT ErrorOr<NonnullRefPtr<NVMeNameSpace>> NVMeNameSpace::try_create(NVMeController const& controller, NonnullRefPtrVector<NVMeQueue> queues, u8 controller_id, u16 nsid, size_t storage_size, size_t lba_size)
 {
     auto minor_number = StorageManagement::generate_storage_minor_number();
     auto major_number = StorageManagement::storage_type_major_number();
     auto device_name_kstring = TRY(KString::formatted("nvme{:d}n{:d}", controller_id, nsid));
-    auto device = TRY(DeviceManagement::try_create_device<NVMeNameSpace>(move(queues), storage_size, lba_size, major_number.value(), minor_number.value(), nsid, move(device_name_kstring)));
+    auto device = TRY(DeviceManagement::try_create_device<NVMeNameSpace>(StorageDevice::LUNAddress { controller.controller_id(), nsid, 0 }, move(queues), storage_size, lba_size, major_number.value(), minor_number.value(), nsid, move(device_name_kstring)));
     return device;
 }
 
-UNMAP_AFTER_INIT NVMeNameSpace::NVMeNameSpace(NonnullRefPtrVector<NVMeQueue> queues, size_t max_addresable_block, size_t lba_size, size_t major_number, size_t minor_number, u16 nsid, NonnullOwnPtr<KString> dev_name)
-    : StorageDevice(major_number, minor_number, lba_size, max_addresable_block, move(dev_name))
+UNMAP_AFTER_INIT NVMeNameSpace::NVMeNameSpace(LUNAddress logical_unit_number_address, NonnullRefPtrVector<NVMeQueue> queues, size_t max_addresable_block, size_t lba_size, size_t major_number, size_t minor_number, u16 nsid, NonnullOwnPtr<KString> dev_name)
+    : StorageDevice(logical_unit_number_address, major_number, minor_number, lba_size, max_addresable_block, move(dev_name))
     , m_nsid(nsid)
     , m_queues(move(queues))
 {

Kernel/Storage/NVMe/NVMeNameSpace.h

@@ -19,17 +19,19 @@
 #include <Kernel/Storage/StorageDevice.h>
 
 namespace Kernel {
+
+class NVMeController;
 class NVMeNameSpace : public StorageDevice {
     friend class DeviceManagement;
 
 public:
-    static ErrorOr<NonnullRefPtr<NVMeNameSpace>> try_create(NonnullRefPtrVector<NVMeQueue> queues, u8 controller_id, u16 nsid, size_t storage_size, size_t lba_size);
+    static ErrorOr<NonnullRefPtr<NVMeNameSpace>> try_create(NVMeController const&, NonnullRefPtrVector<NVMeQueue> queues, u8 controller_id, u16 nsid, size_t storage_size, size_t lba_size);
 
     CommandSet command_set() const override { return CommandSet::NVMe; };
     void start_request(AsyncBlockDeviceRequest& request) override;
 
 private:
-    NVMeNameSpace(NonnullRefPtrVector<NVMeQueue> queues, size_t storage_size, size_t lba_size, size_t major_number, size_t minor_number, u16 nsid, NonnullOwnPtr<KString> early_device_name);
+    NVMeNameSpace(LUNAddress, NonnullRefPtrVector<NVMeQueue> queues, size_t storage_size, size_t lba_size, size_t major_number, size_t minor_number, u16 nsid, NonnullOwnPtr<KString> early_device_name);
 
     virtual InterfaceType interface_type() const override { return InterfaceType::NVMe; }
     u16 m_nsid;

Kernel/Storage/Ramdisk/Device.cpp

@@ -25,8 +25,8 @@ NonnullRefPtr<RamdiskDevice> RamdiskDevice::create(RamdiskController const& cont
     return device_or_error.release_value();
 }
 
-RamdiskDevice::RamdiskDevice(RamdiskController const&, NonnullOwnPtr<Memory::Region>&& region, int major, int minor, NonnullOwnPtr<KString> device_name)
-    : StorageDevice(major, minor, 512, region->size() / 512, move(device_name))
+RamdiskDevice::RamdiskDevice(RamdiskController const& controller, NonnullOwnPtr<Memory::Region>&& region, int major, int minor, NonnullOwnPtr<KString> device_name)
+    : StorageDevice(LUNAddress { controller.controller_id(), 0, 0 }, major, minor, 512, region->size() / 512, move(device_name))
     , m_region(move(region))
 {
     dmesgln("Ramdisk: Device #{} @ {}, Capacity={}", minor, m_region->vaddr(), max_addressable_block() * 512);

Kernel/Storage/StorageController.cpp

@@ -0,0 +1,17 @@
+/*
+ * Copyright (c) 2022, Liav A. <liavalb@hotmail.co.il>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <Kernel/Storage/StorageController.h>
+#include <Kernel/Storage/StorageManagement.h>
+
+namespace Kernel {
+
+StorageController::StorageController()
+    : m_controller_id(StorageManagement::generate_controller_id())
+{
+}
+
+}

Kernel/Storage/StorageController.h

@@ -29,10 +29,17 @@ public:
     virtual RefPtr<StorageDevice> device(u32 index) const = 0;
     virtual size_t devices_count() const = 0;
 
+    u32 controller_id() const { return m_controller_id; }
+
 protected:
     virtual bool reset() = 0;
     virtual bool shutdown() = 0;
 
     virtual void complete_current_request(AsyncDeviceRequest::RequestResult) = 0;
+
+    StorageController();
+
+private:
+    u32 const m_controller_id { 0 };
 };
 }

Kernel/Storage/StorageDevice.cpp

@@ -14,9 +14,10 @@
 
 namespace Kernel {
 
-StorageDevice::StorageDevice(MajorNumber major, MinorNumber minor, size_t sector_size, u64 max_addressable_block, NonnullOwnPtr<KString> device_name)
+StorageDevice::StorageDevice(LUNAddress logical_unit_number_address, MajorNumber major, MinorNumber minor, size_t sector_size, u64 max_addressable_block, NonnullOwnPtr<KString> device_name)
     : BlockDevice(major, minor, sector_size)
     , m_early_storage_device_name(move(device_name))
+    , m_logical_unit_number_address(logical_unit_number_address)
     , m_max_addressable_block(max_addressable_block)
     , m_blocks_per_page(PAGE_SIZE / block_size())
 {

Kernel/Storage/StorageDevice.h

@@ -45,6 +45,20 @@ public:
         NVMe,
     };
 
+    // Note: The most reliable way to address this device from userspace interfaces,
+    // such as SysFS, is to have one way to enumerate everything in the eyes of userspace.
+    // Therefore, SCSI LUN (logical unit number) addressing seem to be the most generic way to do this.
+    // For example, on a legacy ATA instance, one might connect an harddrive to the second IDE controller,
+    // to the Primary channel as a slave device, which translates to LUN 1:0:1.
+    // On NVMe, for example, connecting a second PCIe NVMe storage device as a sole NVMe namespace translates
+    // to LUN 1:0:0.
+    // TODO: LUNs are also useful also when specifying the boot drive on boot. Consider doing that.
+    struct LUNAddress {
+        u32 controller_id;
+        u32 target_id;
+        u32 disk_id;
+    };
+
 public:
     virtual u64 max_addressable_block() const { return m_max_addressable_block; }
 
@@ -62,6 +76,8 @@ public:
 
     void add_partition(NonnullRefPtr<DiskPartition> disk_partition) { MUST(m_partitions.try_append(disk_partition)); }
 
+    LUNAddress const& logical_unit_number_address() const { return m_logical_unit_number_address; }
+
     virtual CommandSet command_set() const = 0;
 
     StringView interface_type_to_string_view() const;
@@ -71,7 +87,7 @@ public:
     virtual ErrorOr<void> ioctl(OpenFileDescription&, unsigned request, Userspace<void*> arg) final;
 
 protected:
-    StorageDevice(MajorNumber, MinorNumber, size_t, u64, NonnullOwnPtr<KString>);
+    StorageDevice(LUNAddress, MajorNumber, MinorNumber, size_t, u64, NonnullOwnPtr<KString>);
     // ^DiskDevice
     virtual StringView class_name() const override;
 
@@ -82,6 +98,7 @@ private:
 
     // FIXME: Remove this method after figuring out another scheme for naming.
     NonnullOwnPtr<KString> m_early_storage_device_name;
+    LUNAddress const m_logical_unit_number_address;
     u64 m_max_addressable_block { 0 };
     size_t m_blocks_per_page { 0 };
 };

Kernel/Storage/StorageManagement.cpp

@@ -30,6 +30,7 @@ namespace Kernel {
 
 static Singleton<StorageManagement> s_the;
 static Atomic<u32> s_device_minor_number;
+static Atomic<u32> s_controller_id;
 
 static constexpr StringView partition_uuid_prefix = "PARTUUID:"sv;
 
@@ -244,6 +245,13 @@ MinorNumber StorageManagement::generate_storage_minor_number()
     return minor_number;
 }
 
+u32 StorageManagement::generate_controller_id()
+{
+    auto controller_id = s_controller_id.load();
+    s_controller_id++;
+    return controller_id;
+}
+
 NonnullRefPtr<FileSystem> StorageManagement::root_filesystem() const
 {
     auto boot_device_description = boot_block_device();

Kernel/Storage/StorageManagement.h

@@ -31,6 +31,8 @@ public:
     static MajorNumber storage_type_major_number();
     static MinorNumber generate_storage_minor_number();
 
+    static u32 generate_controller_id();
+
     void remove_device(StorageDevice&);
 
 private: