@samitouri / QOSAMI-WSL-2 / commits / 8ae97be6

virtiofs: exit QueryVirtiofsMountSource early if virtiofs disabled (#14149)

Co-authored-by: Ben Hillis <benhill@ntdev.microsoft.com>

Ben Hillis committed Feb 3, 2026 at 18:02 UTC 8ae97be65077126e4a29349d986e668c86412056

6 files changed +71 -34

src/linux/init/config.cpp

+3 -8

@@ -679,12 +679,7 @@ try

679 //

680

681 Config.FeatureFlags = Message->FeatureFlags;

682 - char FeatureFlagsString[10];

683 - snprintf(FeatureFlagsString, sizeof(FeatureFlagsString), "%x", Config.FeatureFlags.value());

684 - if (setenv(WSL_FEATURE_FLAGS_ENV, FeatureFlagsString, 1) < 0)

685 - {

686 - LOG_ERROR("setenv failed {}", errno);

687 - }

682 + UtilSetFeatureFlags(Config.FeatureFlags.value());

683

684 //

685 // Determine the default UID which can be specified in /etc/wsl.conf.

@@ -2413,7 +2408,7 @@ try

2408

2409 NewMountOptions = MountEntry.MountOptions;

2410 NewMountOptions += ',';

2416 - if (WSL_USE_VIRTIO_9P(Config))

2411 + if (WSL_USE_VIRTIO_9P())

2412 {

2413 //

2414 // Check if the existing mount is a drvfs mount that needs to be remounted.

@@ -2446,7 +2441,7 @@ try

2441 NewMountOptions += ',';

2442 }

2443

2449 - MountPlan9Share(NewSource, MountEntry.MountPoint, NewMountOptions.c_str(), Message->Admin, Config);

2444 + MountPlan9Share(NewSource, MountEntry.MountPoint, NewMountOptions.c_str(), Message->Admin);

2445 }

2446 else if (strcmp(MountEntry.FileSystemType, VIRTIO_FS_TYPE) == 0)

2447 {

src/linux/init/config.h

+2 -2

@@ -23,8 +23,8 @@ Abstract:

23 #include "SocketChannel.h"

24 #include "WslDistributionConfig.h"

26 -#define WSL_USE_VIRTIO_9P(_Config) (WI_IsFlagSet(UtilGetFeatureFlags((_Config)), LxInitFeatureVirtIo9p))

27 -#define WSL_USE_VIRTIO_FS(_Config) (WI_IsFlagSet(UtilGetFeatureFlags((_Config)), LxInitFeatureVirtIoFs))

26 +#define WSL_USE_VIRTIO_9P() (WI_IsFlagSet(UtilGetFeatureFlags(), LxInitFeatureVirtIo9p))

27 +#define WSL_USE_VIRTIO_FS() (WI_IsFlagSet(UtilGetFeatureFlags(), LxInitFeatureVirtIoFs))

28 #define WSLG_SHARED_FOLDER "wslg"

30 #define INIT_MAKE_SECURITY(_uid, _gid, _mode) {_uid, _gid, _mode}

src/linux/init/drvfs.cpp

+23 -6

@@ -298,7 +298,7 @@ try

298 {

299 return MountFilesystem(DRVFS_FS_TYPE, Source, Target, Options, ExitCode);

300 }

301 - else if (WSL_USE_VIRTIO_FS(Config))

301 + else if (WSL_USE_VIRTIO_FS())

302 {

303 return MountVirtioFs(Source, Target, Options, Admin, Config, ExitCode);

304 }

@@ -349,7 +349,7 @@ Return Value:

349 return ExitCode;

350 }

351

352 -int MountPlan9Share(const char* Source, const char* Target, const char* Options, bool Admin, const wsl::linux::WslDistributionConfig& Config, int* ExitCode)

352 +int MountPlan9Share(const char* Source, const char* Target, const char* Options, bool Admin, int* ExitCode)

353

354 /*++

355

@@ -367,8 +367,6 @@ Arguments:

367

368 Admin - Supplies a boolean specifying if the admin share should be used.

369

370 - Config - Supplies the distribution configuration.

371 -

370 ExitCode - Supplies an optional pointer that receives the exit code.

371

372 Return Value:

@@ -379,7 +377,7 @@ Return Value:

377

378 {

379 std::string MountOptions;

382 - if (WSL_USE_VIRTIO_9P(Config))

380 + if (WSL_USE_VIRTIO_9P())

381 {

382 Source = Admin ? LX_INIT_DRVFS_ADMIN_VIRTIO_TAG : LX_INIT_DRVFS_VIRTIO_TAG;

383 MountOptions = std::format("msize=262144,trans=virtio,{}", Options);

@@ -476,7 +474,7 @@ try

474 //

475

476 MountOptions += Plan9Options;

479 - if (MountPlan9Share(Source, Target, MountOptions.c_str(), Elevated, Config, ExitCode) < 0)

477 + if (MountPlan9Share(Source, Target, MountOptions.c_str(), Elevated, ExitCode) < 0)

478 {

479 return -1;

480 }

@@ -515,6 +513,8 @@ Return Value:

513

514 try

515 {

516 + assert(WSL_USE_VIRTIO_FS());

517 +

518 //

519 // Check whether to use the elevated or non-elevated virtiofs server.

520 //

@@ -596,6 +596,8 @@ Return Value:

596

597 try

598 {

599 + assert(WSL_USE_VIRTIO_FS());

600 +

601 wsl::shared::MessageWriter<LX_INIT_REMOUNT_VIRTIOFS_SHARE_MESSAGE> RemountShare(LxInitMessageRemountVirtioFsDevice);

602 RemountShare->Admin = Admin;

603 RemountShare.WriteString(RemountShare->TagOffset, Tag);

@@ -643,6 +645,21 @@ Return Value:

645

646 try

647 {

648 + if (!WSL_USE_VIRTIO_FS())

649 + {

650 + return {};

651 + }

652 +

653 + //

654 + // Validate the tag is a GUID.

655 + //

656 +

657 + const auto Guid = wsl::shared::string::ToGuid(Tag);

658 + if (!Guid)

659 + {

660 + return {};

661 + }

662 +

663 wsl::shared::MessageWriter<LX_INIT_QUERY_VIRTIOFS_SHARE_MESSAGE> QueryShare(LxInitMessageQueryVirtioFsDevice);

664 QueryShare.WriteString(QueryShare->TagOffset, Tag);

665

src/linux/init/drvfs.h

+1 -1

@@ -23,7 +23,7 @@ int MountDrvfs(const char* Source, const char* Target, const char* Options, std:

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

26 -int MountPlan9Share(const char* Source, const char* Target, const char* Options, bool Admin, const wsl::linux::WslDistributionConfig& Config, int* ExitCode = nullptr);

26 +int MountPlan9Share(const char* Source, const char* Target, const char* Options, bool Admin, int* ExitCode = nullptr);

28 int MountPlan9(const char* Source, const char* Target, const char* Options, std::optional<bool> Admin, const wsl::linux::WslDistributionConfig& Config, int* ExitCode);

src/linux/init/util.cpp

+39 -16

@@ -53,6 +53,7 @@ Abstract:

53 #define WSL_MOUNT_OPTION_SEP ','

55 int g_IsVmMode = -1;

56 +static std::optional<int> g_CachedFeatureFlags;

57 static sigset_t g_originalSignals;

58 thread_local std::string g_threadName;

@@ -1119,7 +1120,7 @@ catch (...)

1120 return {};

1121 }

1122

1122 -int UtilGetFeatureFlags(const wsl::linux::WslDistributionConfig& Config)

1123 +int UtilGetFeatureFlags()

1124

1125 /*++

1126

@@ -1130,7 +1131,7 @@ Routine Description:

1131

1132 Arguments:

1133

1133 - Config - Supplies the distribution config.

1134 + None.

1135

1136 Return Value:

1137

@@ -1143,21 +1144,11 @@ Return Value:

1144 // If feature flags are already known, return them.

1145 //

1146

1146 - static std::optional<int> g_CachedFeatureFlags;

1147 if (g_CachedFeatureFlags)

1148 {

1149 return *g_CachedFeatureFlags;

1150 }

1151

1152 - //

1153 - // If an error occurs, just return no features.

1154 - //

1155 -

1156 - if (Config.FeatureFlags.has_value())

1157 - {

1158 - return Config.FeatureFlags.value();

1159 - }

1160 -

1152 //

1153 // Check if the environment variable is present.

1154 //

@@ -1167,9 +1158,7 @@ Return Value:

1158 //

1159

1160 int FeatureFlags = LxInitFeatureNone;

1170 -

1161 const char* FeatureFlagEnv = getenv(WSL_FEATURE_FLAGS_ENV);

1172 -

1162 if (FeatureFlagEnv != nullptr)

1163 {

1164 FeatureFlags = strtol(FeatureFlagEnv, nullptr, 16);

@@ -1177,7 +1166,7 @@ Return Value:

1166 else

1167 {

1168 //

1180 - // Query init for the value.

1169 + // Query init for the value. If an error occurs, just return no features.

1170 //

1171

1172 wsl::shared::SocketChannel channel{UtilConnectUnix(WSL_INIT_INTEROP_SOCKET), "wslinfo"};

@@ -1194,10 +1183,44 @@ Return Value:

1183 FeatureFlags = channel.ReceiveMessage<RESULT_MESSAGE<int32_t>>().Result;

1184 }

1185

1197 - g_CachedFeatureFlags = FeatureFlags;

1186 + UtilSetFeatureFlags(FeatureFlags, FeatureFlagEnv == nullptr);

1187 return FeatureFlags;

1188 }

1189

1190 +void UtilSetFeatureFlags(int FeatureFlags, bool UpdateEnv)

1191 +

1192 +/*++

1193 +

1194 +Routine Description:

1195 +

1196 + This routine sets the feature flags and updates the cached value and environment variable.

1197 +

1198 +Arguments:

1199 +

1200 + FeatureFlags - Supplies the feature flags to set.

1201 +

1202 + UpdateEnv - Supplies a boolean that indicates whether the environment variable should be updated.

1203 +

1204 +Return Value:

1205 +

1206 + None.

1207 +

1208 +--*/

1209 +

1210 +try

1211 +{

1212 + g_CachedFeatureFlags = FeatureFlags;

1213 + if (UpdateEnv)

1214 + {

1215 + auto FeatureFlagsString = std::format("{:x}", FeatureFlags);

1216 + if (setenv(WSL_FEATURE_FLAGS_ENV, FeatureFlagsString.c_str(), 1) < 0)

1217 + {

1218 + LOG_ERROR("setenv({}, {}, 1) failed {}", WSL_FEATURE_FLAGS_ENV, FeatureFlagsString, errno);

1219 + }

1220 + }

1221 +}

1222 +CATCH_LOG()

1223 +

1224 std::optional<LX_MINI_INIT_NETWORKING_MODE> UtilGetNetworkingMode(void)

1225

1226 /*++

src/linux/init/util.h

+3 -1

@@ -223,7 +223,9 @@ std::optional<std::string> UtilGetEnv(const char* Name, char* Environment);

223

224 std::string UtilGetEnvironmentVariable(const char* Name);

225

226 -int UtilGetFeatureFlags(const wsl::linux::WslDistributionConfig& Config);

226 +int UtilGetFeatureFlags();

227 +

228 +void UtilSetFeatureFlags(int FeatureFlags, bool UpdateEnv = true);

229

230 std::optional<LX_MINI_INIT_NETWORKING_MODE> UtilGetNetworkingMode(void);

231