Fix p9 drvfs read only mount regression (#41487)
#41129 introduces a regression where the ";ro" option is passed to the host for p9 shares. However, that option is not supported by the p9 server and causes the mount to fail. This PR removes the special handling of "ro" in the common parser. And use MountParseFlags to add the required virtio option.
Feng Wang committed
Sep 7, 2026 at 10:41 UTC
74c6ac9abb77f336bd4c796146c23cdb90877ed7
2 files changed
+65
-7
src/linux/init/drvfs.cpp
+8
-7
@@ -248,6 +248,8 @@ Arguments:
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Options - Supplies the DrvFs mount options.
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+ Config - Supplies the distribution configuration.
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+
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Return Value:
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A pair representing the 9p mount options, and standard mount options.
@@ -262,13 +264,7 @@ Return Value:
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while (!Options.empty())
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{
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auto Option = UtilStringNextToken(Options, ",");
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- if (Option == "ro")
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- {
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- Plan9Options += ";ro";
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- StandardOptions += "ro,";
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- }
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- else if (
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- (Option == "metadata") || (StartsWith(Option, PLAN9_CASE_OPTION)) || (StartsWith(Option, "uid=")) ||
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+ if ((Option == "metadata") || (StartsWith(Option, PLAN9_CASE_OPTION)) || (StartsWith(Option, "uid=")) ||
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(StartsWith(Option, "gid=")) || (StartsWith(Option, "umask=")) || (StartsWith(Option, "dmask=")) ||
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(StartsWith(Option, "fmask=")) || (StartsWith(Option, PLAN9_SYMLINK_ROOT_OPTION)))
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{
@@ -733,6 +729,11 @@ try
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//
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auto [Plan9Options, MountOptions] = ConvertDrvfsMountOptionsToPlan9(Options ? Options : "", Config);
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+ const auto ParsedOptions = mountutil::MountParseFlags(MountOptions);
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+ if ((ParsedOptions.MountFlags & MS_RDONLY) != 0)
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+ {
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+ Plan9Options += ";ro";
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+ }
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//
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// Construct a request to add a virtiofs share.
test/windows/DrvFsTests.cpp
+57
@@ -507,6 +507,58 @@ public:
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}
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}
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+ static void DrvfsMountReadOnly()
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+ {
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+ const auto testDir = std::filesystem::current_path() / "drvfs-read-only-test";
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+ auto cleanup = wil::scope_exit_log(WI_DIAGNOSTICS_INFO, [&]() {
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+ std::error_code ec;
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+ std::filesystem::remove_all(testDir, ec);
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+ });
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+
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+ struct TestCase
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+ {
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+ std::wstring_view Options;
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+ bool ReadOnly;
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+ };
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+
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+ constexpr TestCase testCases[] = {
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+ {L"ro,umask=222", true},
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+ {L"ro,rw", false},
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+ {L"rw,ro", true},
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+ };
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+
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+ for (size_t index = 0; index < std::size(testCases); ++index)
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+ {
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+ const auto& testCase = testCases[index];
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+ const auto sourceDir = testDir / std::to_string(index);
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+ const auto mountPoint = std::format(L"/tmp/drvfs-read-only-test-{}", index);
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+ auto unmountCleanup = wil::scope_exit_log(WI_DIAGNOSTICS_INFO, [&]() {
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+ LxsstuLaunchWsl(std::format(L"umount '{}'", mountPoint));
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+ LxsstuLaunchWsl(std::format(L"rmdir '{}'", mountPoint));
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+ });
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+
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+ std::filesystem::create_directories(sourceDir);
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+ constexpr auto expected = "read-only mount marker";
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+ {
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+ std::ofstream markerFile(sourceDir / "marker");
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+ markerFile << expected;
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+ }
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+
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+ VERIFY_ARE_EQUAL(LxsstuLaunchWsl(std::format(L"mkdir -p '{}'", mountPoint)), 0);
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+ VERIFY_ARE_EQUAL(
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+ LxsstuLaunchWsl(std::format(L"mount -t drvfs -o '{}' '{}' '{}'", testCase.Options, sourceDir.string(), mountPoint)), 0);
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+
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+ VERIFY_ARE_EQUAL(LxsstuLaunchWsl(std::format(L"findmnt -rn -M '{}' -O {}", mountPoint, testCase.ReadOnly ? L"ro" : L"rw")), 0);
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+
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+ auto [out, err] = LxsstuLaunchWslAndCaptureOutput(std::format(L"cat '{}/marker'", mountPoint));
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+ VERIFY_ARE_EQUAL(wsl::shared::string::MultiByteToWide(expected), out);
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+
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+ const auto writeResult = LxsstuLaunchWsl(std::format(L"touch '{}/write-test'", mountPoint));
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+ VERIFY_ARE_EQUAL(testCase.ReadOnly, writeResult != 0);
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+ VERIFY_ARE_EQUAL(!testCase.ReadOnly, std::filesystem::exists(sourceDir / "write-test"));
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+ }
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+ }
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+
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// DrvFsTests Private Methods
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private:
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static VOID CreateDrvFsTestFiles(bool Metadata)
@@ -1411,6 +1463,11 @@ class WSL1 : public DrvFsTests
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{ \
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DrvFsTests::DrvfsMountManyVirtioFsShares(DrvFsMode::##_mode##, false); \
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} \
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+\
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+ WSL2_TEST_METHOD(DrvfsMountReadOnly) \
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+ { \
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+ DrvFsTests::DrvfsMountReadOnly(); \
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+ } \
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}
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WSL2_DRVFS_TEST_CLASS(Plan9);