@samitouri / QOSAMI-WSL-1 / commits / 0f8ad5b3

virtiofs: Use aggregate share feature in WSLC (#41151)

* initial work * bump nuget * Address old and new feedback * Use dedicated message for wslc virtiofs mount child * formatting * Last format change --------- Co-authored-by: Daman Mulye <damanmulye@microsoft.com>

Daman Mulye committed Jul 24, 2026 at 18:28 UTC 0f8ad5b3a92450fb9ae88a4ace419772752438a7

16 files changed +247 -146

packages.config

+1 -1

@@ -19,7 +19,7 @@

19 <package id="Microsoft.WSL.bsdtar" version="0.0.2-2" />

20 <package id="Microsoft.WSL.Dependencies.amd64fre" version="10.0.27820.1000-250318-1700.rs-base2-hyp" targetFramework="native" />

21 <package id="Microsoft.WSL.Dependencies.arm64fre" version="10.0.27820.1000-250318-1700.rs-base2-hyp" targetFramework="native" />

22 - <package id="Microsoft.WSL.DeviceHost" version="1.2.53-0" />

22 + <package id="Microsoft.WSL.DeviceHost" version="1.2.54-0" />

23 <package id="Microsoft.WSL.Kernel" version="6.18.35.2-1" targetFramework="native" />

24 <package id="Microsoft.WSL.LinuxSdk" version="1.23.0" targetFramework="native" />

25 <package id="Microsoft.WSL.TestData" version="0.5.0" />

src/linux/init/WSLCInit.cpp

+30 -6

@@ -13,6 +13,7 @@ Abstract:

13 --*/

15 #include "util.h"

16 +#include "drvfs.h"

17 #include "SocketChannel.h"

18 #include "message.h"

19 #include "localhost.h"

@@ -668,8 +669,9 @@ void HandleMessageImpl(

669 Transaction.Send(Response);

670 }

671

671 -void HandleMessageImpl(

672 - wsl::shared::SocketChannel& Channel, wsl::shared::Transaction& Transaction, const WSLC_MOUNT& Message, const gsl::span<gsl::byte>& Buffer)

672 +template <typename TMessage>

673 +void HandleMountMessage(

674 + wsl::shared::SocketChannel& Channel, wsl::shared::Transaction& Transaction, const TMessage& Message, const gsl::span<gsl::byte>& Buffer)

675 {

676 WSLC_MOUNT_RESULT response{};

677 response.Header.MessageType = WSLC_MOUNT_RESULT::Type;

@@ -686,10 +688,11 @@ void HandleMessageImpl(

688 return "";

689 };

690

689 - mountutil::ParsedOptions options;

691 + const char* mountOptions = readField(Message.OptionsIndex);

692 + mountutil::ParsedOptions options{};

693 if (Message.OptionsIndex > 0)

694 {

692 - options = mountutil::MountParseFlags(wsl::shared::string::FromSpan(Buffer, Message.OptionsIndex));

695 + options = mountutil::MountParseFlags(mountOptions);

696 }

697

698 const char* source = readField(Message.SourceIndex);

@@ -716,7 +719,16 @@ void HandleMessageImpl(

719 THROW_ERRNO_IF(EINVAL, WI_IsFlagSet(Message.Flags, WSLC_MOUNT::Chroot) && !WI_IsFlagSet(Message.Flags, WSLC_MOUNT::OverlayFs));

720

721 auto type = readField(Message.TypeIndex);

719 - THROW_LAST_ERROR_IF(UtilMount(source, target, type, options.MountFlags, options.StringOptions.c_str(), c_defaultRetryTimeout) < 0);

722 + if constexpr (std::is_same_v<TMessage, WSLC_MOUNT_VIRTIOFS>)

723 + {

724 + const char* childName = readField(Message.ChildNameIndex);

725 + THROW_ERRNO_IF(EINVAL, !wsl::shared::string::IsEqual(type, VIRTIO_FS_TYPE));

726 + THROW_LAST_ERROR_IF(MountVirtioFsChild(source, childName, target, mountOptions) < 0);

727 + }

728 + else

729 + {

730 + THROW_LAST_ERROR_IF(UtilMount(source, target, type, options.MountFlags, options.StringOptions.c_str(), c_defaultRetryTimeout) < 0);

731 + }

732

733 // Workaround for a Linux bug where virtiofs permissions aren't properly propagated when an overlay is mounted on top of a virtiofs share before the permissions have been fetched.

734 // TODO: Remove once fixed upstream.

@@ -818,6 +830,18 @@ void HandleMessageImpl(

830 Transaction.Send<WSLC_MOUNT_RESULT>(response);

831 }

832

833 +void HandleMessageImpl(

834 + wsl::shared::SocketChannel& Channel, wsl::shared::Transaction& Transaction, const WSLC_MOUNT& Message, const gsl::span<gsl::byte>& Buffer)

835 +{

836 + HandleMountMessage(Channel, Transaction, Message, Buffer);

837 +}

838 +

839 +void HandleMessageImpl(

840 + wsl::shared::SocketChannel& Channel, wsl::shared::Transaction& Transaction, const WSLC_MOUNT_VIRTIOFS& Message, const gsl::span<gsl::byte>& Buffer)

841 +{

842 + HandleMountMessage(Channel, Transaction, Message, Buffer);

843 +}

844 +

845 void HandleMessageImpl(

846 wsl::shared::SocketChannel& Channel, wsl::shared::Transaction& Transaction, const WSLC_EXEC& Message, const gsl::span<gsl::byte>& Buffer)

847 {

@@ -1021,7 +1045,7 @@ void ProcessMessage(wsl::shared::SocketChannel& Channel, wsl::shared::Transactio

1045 {

1046 try

1047 {

1024 - HandleMessage<WSLC_GET_DISK, WSLC_MOUNT, WSLC_EXEC, WSLC_FORK, WSLC_CONNECT, WSLC_SIGNAL, WSLC_TTY_RELAY, WSLC_PORT_RELAY, WSLC_UNMOUNT, WSLC_DETACH, WSLC_ACCEPT, WSLC_WATCH_PROCESSES, WSLC_UNIX_CONNECT, WSLC_GET_GUEST_CAPABILITIES, WSLC_LISTDIR>(

1048 + HandleMessage<WSLC_GET_DISK, WSLC_MOUNT, WSLC_MOUNT_VIRTIOFS, WSLC_EXEC, WSLC_FORK, WSLC_CONNECT, WSLC_SIGNAL, WSLC_TTY_RELAY, WSLC_PORT_RELAY, WSLC_UNMOUNT, WSLC_DETACH, WSLC_ACCEPT, WSLC_WATCH_PROCESSES, WSLC_UNIX_CONNECT, WSLC_GET_GUEST_CAPABILITIES, WSLC_LISTDIR>(

1049 Channel, Transaction, Type, Buffer);

1050 }

1051 catch (...)

src/linux/init/drvfs.cpp

+1 -11

@@ -88,13 +88,7 @@ bool IsMountPoint(const std::string& Path)

88 }

89 } // namespace

91 -int MountVirtioFsChild(

92 - const char* Tag,

93 - const char* ChildName,

94 - const char* Target,

95 - const char* Options,

96 - int* ExitCode = nullptr,

97 - std::string_view SubPath = "/")

91 +int MountVirtioFsChild(const char* Tag, const char* ChildName, const char* Target, const char* Options, int* ExitCode, std::string_view SubPath)

92 {

93 if ((strcmp(Tag, LX_INIT_DRVFS_VIRTIO_TAG) != 0 && strcmp(Tag, LX_INIT_DRVFS_ADMIN_VIRTIO_TAG) != 0) ||

94 !wsl::shared::string::ToGuid(ChildName) || SubPath.empty() || SubPath.front() != '/')

@@ -902,10 +896,6 @@ try

896 return {};

897 }

898

905 - //

906 - // Validate the tag is a GUID.

907 - //

908 -

899 std::string mappingName{Tag};

900 if (Root != nullptr)

901 {

src/linux/init/drvfs.h

@@ -30,6 +30,14 @@ struct VirtioFsMountRoot

31 std::optional<VirtioFsMountRoot> ParseAggregateVirtioFsMountRoot(std::string_view Tag, std::string_view Root);

33 +int MountVirtioFsChild(

34 + const char* Tag,

35 + const char* ChildName,

36 + const char* Target,

37 + const char* Options,

38 + int* ExitCode = nullptr,

39 + std::string_view SubPath = "/");

40 +

41 int MountDrvfs(const char* Source, const char* Target, const char* Options, std::optional<bool> Admin, const wsl::linux::WslDistributionConfig& Config, int* ExitCode = nullptr);

43 int MountDrvfsEntry(int Argc, char* Argv[]);

src/linux/init/util.cpp

+6 -6

@@ -878,16 +878,16 @@ try

878 while (MountEnum.Next())

879 {

880 //

881 - // Skip internal virtiofs device mounts. The aggregate virtiofs root and

882 - // its per-share child binds live under VIRTIOFS_MOUNT_DIR and carry the

883 - // same Windows source as the user-facing /mnt/<drive> bind mounts. If

884 - // they were considered, reverse (Windows->Linux) translation could

885 - // return an internal plumbing path (for example

881 + // When translating Windows paths to Linux, skip internal virtiofs

882 + // device mounts. The aggregate virtiofs root and its per-share child

883 + // binds live under VIRTIOFS_MOUNT_DIR and carry the same Windows source

884 + // as the user-facing /mnt/<drive> bind mounts. If they were considered,

885 + // translation could return an internal plumbing path (for example

886 // /run/wsl/virtiofs-mounts/drvfsa/<guid>) instead of the real mount

887 // point such as /mnt/c.

888 //

889

890 - if (UtilIsPathPrefix(MountEnum.Current().MountPoint, VIRTIOFS_MOUNT_DIR, false) > 0)

890 + if (WinPath && UtilIsPathPrefix(MountEnum.Current().MountPoint, VIRTIOFS_MOUNT_DIR, false) > 0)

891 {

892 continue;

893 }

src/shared/inc/defs.h

-5

@@ -52,11 +52,6 @@ inline constexpr std::uint32_t VersionMinor = WSL_PACKAGE_VERSION_MINOR;

52 inline constexpr std::uint32_t VersionRevision = WSL_PACKAGE_VERSION_REVISION;

53 inline constexpr std::tuple<uint32_t, uint32_t, uint32_t> PackageVersion{VersionMajor, VersionMinor, VersionRevision};

55 -// Maximum number of virtiofs shares that can be mounted (with different paths) over the lifetime of a VM.

56 -// This limit is there to avoid a hang when too many virtiofs shares are mounted.

57 -// TODO: Remove once we can use the same PCI devices for all shares.

58 -inline constexpr size_t c_maxVirtioFsShares = 15;

59 -

55 #ifdef WSL_OFFICIAL_BUILD

57 inline constexpr bool OfficialBuild = true;

src/shared/inc/lxinitshared.h

+21

@@ -413,6 +413,7 @@ typedef enum _LX_MESSAGE_TYPE

413 LxMessageWSLCGetGuestCapabilitiesResult,

414 LxMessageWSLCListDir,

415 LxMessageWSLCListDirResult,

416 + LxMessageWSLCMountVirtioFs,

417 } LX_MESSAGE_TYPE,

418 *PLX_MESSAGE_TYPE;

419

@@ -527,6 +528,7 @@ inline auto ToString(LX_MESSAGE_TYPE messageType)

528 X(LxMessageWSLCGetGuestCapabilitiesResult)

529 X(LxMessageWSLCListDir)

530 X(LxMessageWSLCListDirResult)

531 + X(LxMessageWSLCMountVirtioFs)

532

533 default:

534 return "<unexpected LX_MESSAGE_TYPE>";

@@ -1657,6 +1659,25 @@ struct WSLC_MOUNT

1659 PRETTY_PRINT(FIELD(Header), STRING_FIELD(SourceIndex), STRING_FIELD(DestinationIndex), STRING_FIELD(TypeIndex), STRING_FIELD(OptionsIndex));

1660 };

1661

1662 +struct WSLC_MOUNT_VIRTIOFS

1663 +{

1664 + static inline auto Type = LxMessageWSLCMountVirtioFs;

1665 + using TResponse = WSLC_MOUNT_RESULT;

1666 +

1667 + DECLARE_MESSAGE_CTOR(WSLC_MOUNT_VIRTIOFS);

1668 +

1669 + MESSAGE_HEADER Header{};

1670 + unsigned int SourceIndex{};

1671 + unsigned int DestinationIndex{};

1672 + unsigned int TypeIndex{};

1673 + unsigned int OptionsIndex{};

1674 + unsigned int Flags{};

1675 + unsigned int ChildNameIndex{};

1676 + char Buffer[];

1677 +

1678 + PRETTY_PRINT(FIELD(Header), STRING_FIELD(SourceIndex), STRING_FIELD(DestinationIndex), STRING_FIELD(TypeIndex), STRING_FIELD(OptionsIndex), STRING_FIELD(ChildNameIndex));

1679 +};

1680 +

1681 struct WSLC_EXEC

1682 {

1683 static inline auto Type = LxMessageWSLCExec;

src/windows/common/DeviceHostProxy.cpp

@@ -180,6 +180,14 @@ void DeviceHostProxy::AddVirtiofsChild(const GUID& InstanceId, const std::wstrin

180 THROW_IF_FAILED(GetVirtiofsDevice(InstanceId)->AddChild(name.get(), rootPath.get(), mountOptions.get()));

181 }

182

183 +void DeviceHostProxy::RemoveVirtiofsChild(const GUID& InstanceId, const std::wstring& Name)

184 +{

185 + std::lock_guard lifecycleLock(m_deviceLifecycleLock);

186 +

187 + const auto name = wil::make_bstr(Name.c_str());

188 + THROW_IF_FAILED(GetVirtiofsDevice(InstanceId)->RemoveChild(name.get()));

189 +}

190 +

191 GUID DeviceHostProxy::AddVirtioPmemDevice(_In_ HANDLE UserToken, const std::wstring& Path, bool Writable)

192 {

193 std::lock_guard lifecycleLock(m_deviceLifecycleLock);

src/windows/common/DeviceHostProxy.h

@@ -23,6 +23,8 @@ public:

24 void AddVirtiofsChild(const GUID& InstanceId, const std::wstring& Name, const std::wstring& RootPath, const std::wstring& MountOptions);

26 + void RemoveVirtiofsChild(const GUID& InstanceId, const std::wstring& Name);

27 +

28 GUID AddVirtioPmemDevice(_In_ HANDLE UserToken, const std::wstring& Path, bool Writable);

30 void RemoveDevice(const GUID& InstanceId);

src/windows/common/GuestDeviceManager.cpp

@@ -33,6 +33,13 @@ void GuestDeviceManager::AddVirtiofsChild(_In_ const GUID& InstanceId, _In_ PCWS

33 m_deviceHostSupport->AddVirtiofsChild(InstanceId, Name, RootPath, MountOptions ? MountOptions : L"");

34 }

36 +_Requires_lock_not_held_(m_lock)

37 +void GuestDeviceManager::RemoveVirtiofsChild(_In_ const GUID& InstanceId, _In_ PCWSTR Name)

38 +{

39 + auto guestDeviceLock = m_lock.lock_exclusive();

40 + m_deviceHostSupport->RemoveVirtiofsChild(InstanceId, Name);

41 +}

42 +

43 _Requires_lock_not_held_(m_lock)

44 GUID GuestDeviceManager::AddVirtioPmemDevice(_In_ PCWSTR Path, bool ReadOnly, _In_ HANDLE UserToken)

45 {

src/windows/common/GuestDeviceManager.h

@@ -27,6 +27,9 @@ public:

27 _Requires_lock_not_held_(m_lock)

28 void AddVirtiofsChild(_In_ const GUID& InstanceId, _In_ PCWSTR Name, _In_opt_ PCWSTR MountOptions, _In_ PCWSTR RootPath);

30 + _Requires_lock_not_held_(m_lock)

31 + void RemoveVirtiofsChild(_In_ const GUID& InstanceId, _In_ PCWSTR Name);

32 +

33 _Requires_lock_not_held_(m_lock)

34 GUID AddVirtioPmemDevice(_In_ PCWSTR Path, bool ReadOnly, _In_ HANDLE UserToken);

src/windows/service/exe/HcsVirtualMachine.cpp

+11 -2

@@ -620,7 +620,15 @@ try

620 {

621 std::wstring options = ReadOnly ? L"ro" : L"";

622

623 - it->second = m_guestDeviceManager->AddVirtiofsDevice(shareName.c_str(), options.c_str(), WindowsPath, m_userToken.get());

623 + if (!m_virtioFsDevice.has_value())

624 + {

625 + VirtioFsShareOptions aggregateOptions{.Kind = VirtiofsShareKind_Aggregate};

626 + m_virtioFsDevice =

627 + m_guestDeviceManager->AddVirtiofsDevice(TEXT(LX_INIT_DRVFS_VIRTIO_TAG), L"", L"", m_userToken.get(), aggregateOptions);

628 + }

629 +

630 + m_guestDeviceManager->AddVirtiofsChild(m_virtioFsDevice.value(), shareName.c_str(), options.c_str(), WindowsPath);

631 + it->second = m_virtioFsDevice;

632 }

633

634 cleanup.release();

@@ -645,7 +653,8 @@ try

653 }

654 else

655 {

648 - m_guestDeviceManager->RemoveGuestDevice(it->second.value());

656 + auto shareName = wsl::shared::string::GuidToString<wchar_t>(it->first, wsl::shared::string::None);

657 + m_guestDeviceManager->RemoveVirtiofsChild(it->second.value(), shareName.c_str());

658 }

659

660 m_shares.erase(it);

src/windows/service/exe/HcsVirtualMachine.h

+2 -1

@@ -97,8 +97,9 @@ private:

97 std::map<ULONG, DiskInfo> m_attachedDisks;

98 std::bitset<MAX_VHD_COUNT> m_lunBitmap;

100 - // Shares: key is ShareId, value is nullopt for Plan9 or DeviceInstanceId for VirtioFS

100 + // Shares: key is ShareId, value is nullopt for Plan9 or the aggregate DeviceInstanceId for VirtioFS.

101 std::map<GUID, std::optional<GUID>, wsl::windows::common::helpers::GuidLess> m_shares;

102 + std::optional<GUID> m_virtioFsDevice;

103

104 std::filesystem::path m_vmSavedStateFile;

105 std::filesystem::path m_crashDumpFolder;

src/windows/wslcsession/WSLCVirtualMachine.cpp

+30 -43

@@ -886,6 +886,30 @@ void WSLCVirtualMachine::Mount(shared::SocketChannel& Channel, LPCSTR Source, LP

886 THROW_HR_IF(E_FAIL, response.Result != 0);

887 }

888

889 +void WSLCVirtualMachine::MountVirtioFsChild(shared::SocketChannel& Channel, LPCSTR Source, LPCSTR ChildName, LPCSTR Target, LPCSTR Options, ULONG Flags)

890 +{

891 + wsl::shared::MessageWriter<WSLC_MOUNT_VIRTIOFS> message;

892 + message.WriteString(message->SourceIndex, Source);

893 + message.WriteString(message->ChildNameIndex, ChildName);

894 + message.WriteString(message->DestinationIndex, Target);

895 + message.WriteString(message->TypeIndex, "virtiofs");

896 + message.WriteString(message->OptionsIndex, Options);

897 + message->Flags = Flags;

898 +

899 + const auto& response = Channel.Transaction<WSLC_MOUNT_VIRTIOFS>(message.Span());

900 +

901 + WSL_LOG(

902 + "WSLCMountVirtioFsChild",

903 + TraceLoggingValue(Source, "Source"),

904 + TraceLoggingValue(ChildName, "ChildName"),

905 + TraceLoggingValue(Target, "Target"),

906 + TraceLoggingValue(Options, "Options"),

907 + TraceLoggingValue(Flags, "Flags"),

908 + TraceLoggingValue(response.Result, "Result"));

909 +

910 + THROW_HR_IF(E_FAIL, response.Result != 0);

911 +}

912 +

913 int32_t WSLCVirtualMachine::ExpectClosedChannelOrError(wsl::shared::SocketChannel& Channel)

914 {

915 auto [response, span] = Channel.ReceiveMessageOrClosed<RESULT_MESSAGE<int32_t>>();

@@ -1077,9 +1101,7 @@ try

1101 THROW_HR_IF_MSG(E_INVALIDARG, LinuxPath[0] != '/', "Mountpoint is not absolute: '%hs'", LinuxPath);

1102

1103 const bool readOnly = WI_IsFlagSet(Flags, WSLCMountFlagsReadOnly);

1080 - auto normalizedPath = std::filesystem::weakly_canonical(path).wstring();

1104 GUID shareGuid{};

1082 - bool reusingShare = false;

1105

1106 {

1107 std::lock_guard lock(m_lock);

@@ -1088,34 +1110,8 @@ try

1110 auto it = m_mountedWindowsFolders.find(LinuxPath);

1111 THROW_HR_IF(HRESULT_FROM_WIN32(ERROR_ALREADY_EXISTS), it != m_mountedWindowsFolders.end());

1112

1091 - // In VirtioFs mode, try to reuse an existing share for the same Windows path and access mode.

1092 - if (FeatureEnabled(WslcFeatureFlagsVirtioFs))

1093 - {

1094 - auto shareIt = m_virtioFsShares.find({normalizedPath, readOnly});

1095 - if (shareIt != m_virtioFsShares.end())

1096 - {

1097 - shareGuid = shareIt->second;

1098 - reusingShare = true;

1099 - }

1100 - else

1101 - {

1102 - THROW_HR_WITH_USER_ERROR_IF(

1103 - E_OUTOFMEMORY,

1104 - shared::Localization::MessageWslcTooManyVirtioFsShares(shared::c_maxVirtioFsShares),

1105 - m_virtioFsShares.size() >= shared::c_maxVirtioFsShares);

1106 - }

1107 - }

1108 -

1109 - if (!reusingShare)

1110 - {

1111 - // Delegate to IWSLCVirtualMachine for the privileged share creation

1112 - THROW_IF_FAILED(m_vm->AddShare(WindowsPath, readOnly, &shareGuid));

1113 -

1114 - if (FeatureEnabled(WslcFeatureFlagsVirtioFs))

1115 - {

1116 - m_virtioFsShares[{normalizedPath, readOnly}] = shareGuid;

1117 - }

1118 - }

1113 + // Delegate to IWSLCVirtualMachine for the privileged share creation.

1114 + THROW_IF_FAILED(m_vm->AddShare(WindowsPath, readOnly, &shareGuid));

1115

1116 m_mountedWindowsFolders.emplace(LinuxPath, shareGuid);

1117 }

@@ -1126,11 +1122,7 @@ try

1122 if (WI_VERIFY(mountIt != m_mountedWindowsFolders.end()))

1123 {

1124 m_mountedWindowsFolders.erase(mountIt);

1129 - if (!FeatureEnabled(WslcFeatureFlagsVirtioFs))

1130 - {

1131 - m_virtioFsShares.erase({normalizedPath, readOnly});

1132 - LOG_IF_FAILED(m_vm->RemoveShare(shareGuid));

1133 - }

1125 + LOG_IF_FAILED(m_vm->RemoveShare(shareGuid));

1126 }

1127 });

1128

@@ -1154,7 +1146,7 @@ try

1146 else

1147 {

1148 std::string options = readOnly ? "ro" : "rw";

1157 - Mount(m_initChannel, shareName.c_str(), LinuxPath, "virtiofs", options.c_str(), Flags);

1149 + MountVirtioFsChild(m_initChannel, LX_INIT_DRVFS_VIRTIO_TAG, shareName.c_str(), LinuxPath, options.c_str(), Flags);

1150 }

1151

1152 deleteOnFailure.release();

@@ -1178,13 +1170,8 @@ try

1170

1171 auto shareId = it->second;

1172

1181 - // Keep the share mounted in virtiofs mode to avoid accumulating devices, which can cause a hang when reached.

1182 - // TODO: Actually remove the device once this is supported by the device host.

1183 - if (!FeatureEnabled(WslcFeatureFlagsVirtioFs))

1184 - {

1185 - // Delegate to IWSLCVirtualMachine for the privileged share removal

1186 - THROW_IF_FAILED(m_vm->RemoveShare(shareId));

1187 - }

1173 + // Delegate to IWSLCVirtualMachine for the privileged share removal.

1174 + THROW_IF_FAILED(m_vm->RemoveShare(shareId));

1175

1176 m_mountedWindowsFolders.erase(it);

1177

src/windows/wslcsession/WSLCVirtualMachine.h

+2 -4

@@ -204,6 +204,8 @@ private:

204 void ReadGuestCapabilities();

205

206 static void Mount(wsl::shared::SocketChannel& Channel, LPCSTR Source, _In_ LPCSTR Target, _In_ LPCSTR Type, _In_ LPCSTR Options, _In_ ULONG Flags);

207 + static void MountVirtioFsChild(

208 + wsl::shared::SocketChannel& Channel, _In_ LPCSTR Source, _In_ LPCSTR ChildName, _In_ LPCSTR Target, _In_ LPCSTR Options, _In_ ULONG Flags);

209 void MountGpuLibraries(_In_ LPCSTR LibrariesMountPoint, _In_ LPCSTR DriversMountpoint);

210

211 Microsoft::WRL::ComPtr<WSLCProcess> CreateLinuxProcessImpl(

@@ -280,10 +282,6 @@ private:

282 std::map<ULONG, AttachedDisk> m_attachedDisks;

283 std::map<std::string, GUID> m_mountedWindowsFolders;

284

283 - // VirtioFs share cache: maps (normalized WindowsPath, readOnly) to share GUID.

284 - // Shares are kept alive after unmount for reuse on subsequent mounts of the same folder.

285 - std::map<std::pair<std::wstring, bool>, GUID> m_virtioFsShares;

286 -

285 std::recursive_mutex m_lock;

286 std::mutex m_portRelaylock;

287 };

test/windows/WSLCTests.cpp

+115 -67

@@ -3763,19 +3763,20 @@ class WSLCTests

3763 VERIFY_SUCCEEDED(session->MountWindowsFolder(testFolder.c_str(), "/win-path", true));

3764 ExpectMount(session.get(), "/win-path", expectedMountOptions(true));

3765

3766 - // Capture the mount source and type, unmount, then remount without read-only.

3766 + // Remount a bind of the share as read-write to ensure the device host still enforces read-only access.

3767 ExpectCommandResult(

3768 session.get(),

3769 {"/bin/sh",

3770 "-c",

3771 - "src=$(findmnt -n -o SOURCE /win-path) && "

3772 - "fstype=$(findmnt -n -o FSTYPE /win-path) && "

3773 - "umount /win-path && "

3774 - "mount -t $fstype $src /win-path"},

3771 + "mkdir -p /win-path-rw && "

3772 + "mount --bind /win-path /win-path-rw && "

3773 + "mount -o remount,bind,rw /win-path-rw && "

3774 + "findmnt -n -o VFS-OPTIONS /win-path-rw | grep -qE '(^|,)rw(,|$)'"},

3775 0);

3776

3777 - // Verify the folder is still not writeable.

3778 - ExpectCommandResult(session.get(), {"/bin/sh", "-c", "echo -n content > /win-path/file.txt"}, 1);

3777 + // Verify the folder is still not writeable through the read-write bind.

3778 + ExpectCommandResult(session.get(), {"/bin/sh", "-c", "echo -n content > /win-path-rw/file.txt"}, 1);

3779 + ExpectCommandResult(session.get(), {"/bin/sh", "-c", "umount /win-path-rw && rmdir /win-path-rw"}, 0);

3780

3781 VERIFY_SUCCEEDED(session->UnmountWindowsFolder("/win-path"));

3782 ExpectMount(session.get(), "/win-path", {});

@@ -3809,107 +3810,154 @@ class WSLCTests

3810 ValidateWindowsMounts(true);

3811 }

3812

3812 - // Validates that VirtioFs shares are reused across mount/unmount cycles for the same Windows folder.

3813 - WSLC_TEST_METHOD(WindowsMountsVirtioFsShareReuse)

3813 + // Validates that each mount owns an independent child on the shared aggregate device.

3814 + WSLC_TEST_METHOD(WindowsMountsVirtioFsIndependentShares)

3815 {

3815 - auto settings = GetDefaultSessionSettings(L"virtiofs-share-reuse-test");

3816 + auto settings = GetDefaultSessionSettings(L"virtiofs-independent-shares-test");

3817 WI_SetFlag(settings.FeatureFlags, WslcFeatureFlagsVirtioFs);

3818

3819 auto createNewSession = !WI_IsFlagSet(m_defaultSessionSettings.FeatureFlags, WslcFeatureFlagsVirtioFs);

3820 auto session = createNewSession ? CreateSession(settings) : m_defaultSession;

3821

3821 - auto testFolder = std::filesystem::current_path() / "test-folder-share-reuse";

3822 + auto testFolder = std::filesystem::current_path() / "test-folder-independent-shares";

3823 std::filesystem::create_directories(testFolder);

3824 + std::ofstream(testFolder / "marker.txt") << "content";

3825 auto cleanup = wil::scope_exit_log(WI_DIAGNOSTICS_INFO, [&]() { std::filesystem::remove_all(testFolder); });

3826

3825 - auto getMountSource = [&](const char* mountPoint) -> std::string {

3826 - auto cmd = std::format("findmnt -n -o SOURCE {}", mountPoint);

3827 + auto getMountField = [&](const char* mountPoint, const char* field) -> std::string {

3828 + auto cmd = std::format("findmnt -n -o {} {}", field, mountPoint);

3829 auto result = ExpectCommandResult(session.get(), {"/bin/sh", "-c", cmd}, 0);

3830 return result.Output[1];

3831 };

3832

3831 - // Mount, capture the source (share GUID), unmount, remount, verify same GUID is reused.

3833 + // Concurrent mounts of the same host path use distinct children on the same aggregate device.

3834 {

3833 - VERIFY_SUCCEEDED(session->MountWindowsFolder(testFolder.c_str(), "/win-path", false));

3834 - auto firstSource = getMountSource("/win-path");

3835 - VERIFY_IS_FALSE(firstSource.empty());

3835 + VERIFY_SUCCEEDED(session->MountWindowsFolder(testFolder.c_str(), "/win-path-1", false));

3836 + VERIFY_SUCCEEDED(session->MountWindowsFolder(testFolder.c_str(), "/win-path-2", false));

3837

3837 - VERIFY_SUCCEEDED(session->UnmountWindowsFolder("/win-path"));

3838 - ExpectMount(session.get(), "/win-path", {});

3838 + auto firstDevice = getMountField("/win-path-1", "MAJ:MIN");

3839 + auto secondDevice = getMountField("/win-path-2", "MAJ:MIN");

3840 + auto firstRoot = getMountField("/win-path-1", "FSROOT");

3841 + auto secondRoot = getMountField("/win-path-2", "FSROOT");

3842 + VERIFY_ARE_EQUAL(firstDevice, secondDevice);

3843 + VERIFY_ARE_NOT_EQUAL(firstRoot, secondRoot);

3844 + VERIFY_IS_TRUE(firstRoot.starts_with('/'));

3845 + VERIFY_IS_TRUE(firstRoot.ends_with('\n'));

3846 + VERIFY_IS_TRUE(secondRoot.starts_with('/'));

3847 + VERIFY_IS_TRUE(secondRoot.ends_with('\n'));

3848 + firstRoot.pop_back();

3849 + secondRoot.pop_back();

3850

3840 - // Remount the same folder - should reuse the same share GUID.

3841 - VERIFY_SUCCEEDED(session->MountWindowsFolder(testFolder.c_str(), "/win-path", false));

3842 - auto secondSource = getMountSource("/win-path");

3851 + const auto firstChild = std::format("/run/wsl/virtiofs-mounts/{}{}", LX_INIT_DRVFS_VIRTIO_TAG, firstRoot);

3852 + const auto secondChild = std::format("/run/wsl/virtiofs-mounts/{}{}", LX_INIT_DRVFS_VIRTIO_TAG, secondRoot);

3853

3844 - VERIFY_ARE_EQUAL(firstSource, secondSource);

3854 + VERIFY_SUCCEEDED(session->UnmountWindowsFolder("/win-path-1"));

3855 + ExpectCommandResult(session.get(), {"/bin/cat", "/win-path-2/marker.txt"}, 0);

3856 + ExpectCommandResult(session.get(), {"/usr/bin/test", "!", "-e", firstChild}, 0);

3857 + ExpectCommandResult(session.get(), {"/usr/bin/test", "-e", secondChild}, 0);

3858

3846 - VERIFY_SUCCEEDED(session->UnmountWindowsFolder("/win-path"));

3859 + VERIFY_SUCCEEDED(session->UnmountWindowsFolder("/win-path-2"));

3860 + ExpectCommandResult(session.get(), {"/usr/bin/test", "!", "-e", secondChild}, 0);

3861 }

3862

3849 - // Verify that changing the read-only flag produces a different share GUID.

3863 + // Verify that read-write and read-only shares use different children on the same aggregate device.

3864 {

3851 - VERIFY_SUCCEEDED(session->MountWindowsFolder(testFolder.c_str(), "/win-path", false));

3852 - auto rwSource = getMountSource("/win-path");

3865 + VERIFY_SUCCEEDED(session->MountWindowsFolder(testFolder.c_str(), "/win-path-rw", false));

3866 + VERIFY_SUCCEEDED(session->MountWindowsFolder(testFolder.c_str(), "/win-path-ro", true));

3867

3854 - VERIFY_SUCCEEDED(session->UnmountWindowsFolder("/win-path"));

3868 + auto rwDevice = getMountField("/win-path-rw", "MAJ:MIN");

3869 + auto roDevice = getMountField("/win-path-ro", "MAJ:MIN");

3870 + auto rwRoot = getMountField("/win-path-rw", "FSROOT");

3871 + auto roRoot = getMountField("/win-path-ro", "FSROOT");

3872

3856 - VERIFY_SUCCEEDED(session->MountWindowsFolder(testFolder.c_str(), "/win-path", true));

3857 - auto roSource = getMountSource("/win-path");

3873 + VERIFY_ARE_EQUAL(rwDevice, roDevice);

3874 + VERIFY_ARE_NOT_EQUAL(rwRoot, roRoot);

3875

3859 - VERIFY_ARE_NOT_EQUAL(rwSource, roSource);

3860 -

3861 - VERIFY_SUCCEEDED(session->UnmountWindowsFolder("/win-path"));

3876 + VERIFY_SUCCEEDED(session->UnmountWindowsFolder("/win-path-rw"));

3877 + VERIFY_SUCCEEDED(session->UnmountWindowsFolder("/win-path-ro"));

3878 }

3879 }

3880

3865 - // Validate that the correct error is returned when too many virtiofs shares are mounted.

3866 - WSLC_TEST_METHOD(VirtiofsVolumesLimit)

3881 + WSLC_TEST_METHOD(WindowsMountsVirtioFsRemoveChild)

3882 {

3868 - constexpr size_t c_maxVirtioFsShares = wsl::shared::c_maxVirtioFsShares;

3883 + auto settings = GetDefaultSessionSettings(L"virtiofs-remove-child-test");

3884 + WI_SetFlag(settings.FeatureFlags, WslcFeatureFlagsVirtioFs);

3885 + auto session = CreateSession(settings);

3886 +

3887 + const auto testRoot = std::filesystem::current_path() / "test-folder-remove-child";

3888 + const auto firstFolder = testRoot / "first";

3889 + const auto secondFolder = testRoot / "second";

3890 + std::filesystem::create_directories(firstFolder);

3891 + std::filesystem::create_directories(secondFolder);

3892 + std::ofstream(firstFolder / "marker.txt") << "first";

3893 + std::ofstream(secondFolder / "marker.txt") << "second";

3894 + auto cleanup = wil::scope_exit_log(WI_DIAGNOSTICS_INFO, [&]() { std::filesystem::remove_all(testRoot); });

3895 +

3896 + auto getMountRoot = [&](const char* mountPoint) {

3897 + const auto command = std::format("findmnt -n -o FSROOT {}", mountPoint);

3898 + auto root = ExpectCommandResult(session.get(), {"/bin/sh", "-c", command}, 0).Output.at(1);

3899 + VERIFY_IS_TRUE(root.starts_with('/'));

3900 + VERIFY_IS_TRUE(root.ends_with('\n'));

3901 + root.pop_back();

3902 + return root;

3903 + };

3904 +

3905 + VERIFY_SUCCEEDED(session->MountWindowsFolder(firstFolder.c_str(), "/remove-child-first", false));

3906 + VERIFY_SUCCEEDED(session->MountWindowsFolder(secondFolder.c_str(), "/remove-child-second", false));

3907

3870 - auto settings = GetDefaultSessionSettings(L"virtiofs-share-limit-test");

3908 + const auto firstRoot = getMountRoot("/remove-child-first");

3909 + const auto secondRoot = getMountRoot("/remove-child-second");

3910 + VERIFY_ARE_NOT_EQUAL(firstRoot, secondRoot);

3911 +

3912 + const auto aggregateRoot = std::format("/run/wsl/virtiofs-mounts/{}", LX_INIT_DRVFS_VIRTIO_TAG);

3913 + const auto firstChild = aggregateRoot + firstRoot;

3914 + const auto secondChild = aggregateRoot + secondRoot;

3915 + ExpectCommandResult(session.get(), {"/usr/bin/test", "-e", firstChild}, 0);

3916 + ExpectCommandResult(session.get(), {"/usr/bin/test", "-e", secondChild}, 0);

3917 +

3918 + VERIFY_SUCCEEDED(session->UnmountWindowsFolder("/remove-child-first"));

3919 + ExpectCommandResult(session.get(), {"/usr/bin/test", "!", "-e", firstChild}, 0);

3920 + ExpectCommandResult(session.get(), {"/bin/cat", "/remove-child-second/marker.txt"}, 0);

3921 + ExpectCommandResult(session.get(), {"/usr/bin/test", "-e", secondChild}, 0);

3922 +

3923 + VERIFY_SUCCEEDED(session->UnmountWindowsFolder("/remove-child-second"));

3924 + ExpectCommandResult(session.get(), {"/usr/bin/test", "!", "-e", secondChild}, 0);

3925 + }

3926 +

3927 + // Validate that enough VirtioFs shares can be mounted to exceed the old per-device aperture limit.

3928 + WSLC_TEST_METHOD(VirtiofsMountManyVolumes)

3929 + {

3930 + constexpr size_t c_shareCount = 32;

3931 +

3932 + auto settings = GetDefaultSessionSettings(L"virtiofs-many-shares-test");

3933 WI_SetFlag(settings.FeatureFlags, WslcFeatureFlagsVirtioFs);

3934

3873 - // Use a dedicated session so the share count starts at zero (no GPU libraries are mounted).

3935 auto session = CreateSession(settings);

3936

3876 - auto testRoot = std::filesystem::current_path() / "test-folder-share-limit";

3937 + auto testRoot = std::filesystem::current_path() / "test-folder-many-shares";

3938 std::filesystem::create_directories(testRoot);

3939 auto cleanup = wil::scope_exit_log(WI_DIAGNOSTICS_INFO, [&]() { std::filesystem::remove_all(testRoot); });

3940 + std::vector<std::string> mountPoints;

3941

3880 - auto folderForIndex = [&](size_t index) {

3881 - auto folder = testRoot / std::to_string(index);

3882 - std::filesystem::create_directories(folder);

3883 - return folder;

3884 - };

3885 -

3886 - // Mount distinct Windows folders (each creates a new share) until the limit is reached.

3887 - size_t mounted = 0;

3888 - HRESULT lastResult = S_OK;

3889 - for (size_t i = 0; i <= c_maxVirtioFsShares; ++i)

3942 + for (size_t index = 0; index < c_shareCount; ++index)

3943 {

3891 - auto folder = folderForIndex(i);

3892 - auto mountPoint = std::format("/vfs-limit-{}", i);

3944 + const auto folder = testRoot / std::to_string(index);

3945 + std::filesystem::create_directories(folder);

3946 + std::ofstream(folder / "marker.txt") << index;

3947

3894 - lastResult = session->MountWindowsFolder(folder.c_str(), mountPoint.c_str(), false);

3895 - if (FAILED(lastResult))

3896 - {

3897 - break;

3898 - }

3948 + const auto mountPoint = std::format("/vfs-many-{}", index);

3949 + VERIFY_SUCCEEDED(session->MountWindowsFolder(folder.c_str(), mountPoint.c_str(), false));

3950 + mountPoints.emplace_back(mountPoint);

3951

3900 - mounted++;

3952 + const auto command = std::format("cat {}/marker.txt", mountPoint);

3953 + const auto result = ExpectCommandResult(session.get(), {"/bin/sh", "-c", command}, 0);

3954 + VERIFY_ARE_EQUAL(std::to_string(index), result.Output.at(1));

3955 }

3956

3903 - VERIFY_ARE_EQUAL(mounted, c_maxVirtioFsShares);

3904 - VERIFY_ARE_EQUAL(lastResult, E_OUTOFMEMORY);

3905 - ValidateCOMErrorMessage(

3906 - L"Too many volumes have been mounted (limit: 15). Restart the session to mount more volumes. This will be fixed in a "

3907 - L"future release.");

3908 -

3909 - // Reusing an already-created share must still succeed.

3910 - auto reusedFolder = folderForIndex(0);

3911 - VERIFY_SUCCEEDED(session->MountWindowsFolder(reusedFolder.c_str(), "/vfs-limit-reuse", false));

3912 - VERIFY_SUCCEEDED(session->UnmountWindowsFolder("/vfs-limit-reuse"));

3957 + for (const auto& mountPoint : mountPoints)

3958 + {

3959 + VERIFY_SUCCEEDED(session->UnmountWindowsFolder(mountPoint.c_str()));

3960 + }

3961 }

3962

3963 // This test case validates that no file descriptors are leaked to user processes.