drvfs: add per-mount transport= option for cross-OS filesystem benchmarking#40608
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benhillis wants to merge 1 commit into
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drvfs: add per-mount transport= option for cross-OS filesystem benchmarking#40608benhillis wants to merge 1 commit into
benhillis wants to merge 1 commit into
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Pull request overview
Adds support for selecting DrvFs’ cross-OS filesystem transport on a per-mount basis (via -o transport=...) to enable side-by-side benchmarking of plan9-over-hvsocket, virtio-9p, and virtiofs within a single WSL2 VM. This includes a new experimental .wslconfig switch intended to stand up multiple backends concurrently, plus new Windows tests and updated documentation.
Changes:
- Guest (
mount.drvfs): parse/striptransport=from mount options and route the mount to plan9 / virtio9p / virtiofs accordingly. - Host: add
experimental.drvFsTransportsconfig and adjust VM/share setup logic to make additional transports available. - Tests/docs: add TAEF coverage for the override and document usage + experimental flag.
Reviewed changes
Copilot reviewed 10 out of 10 changed files in this pull request and generated 5 comments.
Show a summary per file
| File | Description |
|---|---|
| test/windows/DrvFsTests.cpp | Adds a new test class validating transport= behavior, stripping, invalid values, and backend availability. |
| test/windows/Common.h | Extends test config defaults with drvFsTransports. |
| test/windows/Common.cpp | Emits [experimental] drvFsTransports=... into generated .wslconfig test configs. |
| src/windows/service/exe/WslCoreVm.cpp | Updates share registration to optionally expose multiple Plan9 transports and tweaks virtiofs availability checks. |
| src/windows/common/WslCoreConfig.h | Adds experimental.drvFsTransports config key + helper predicates for transport availability. |
| src/windows/common/WslCoreConfig.cpp | Parses/validates the new experimental setting and enforces compatibility constraints. |
| src/linux/init/drvfs.h | Introduces DrvFsTransport enum and new function signatures for transport override plumbing. |
| src/linux/init/drvfs.cpp | Implements option parsing/dispatch and adds virtiofs no-fallback mode for explicit transport requests. |
| src/linux/init/config.cpp | Detects existing Plan9 transport during remount to preserve the actual transport in experimental multi-transport scenarios. |
| doc/docs/technical-documentation/drvfs.md | Documents transport= option and the experimental drvFsTransports switch. |
| @@ -871,47 +871,65 @@ _Requires_lock_held_(m_guestDeviceLock) | |||
| void WslCoreVm::AddPlan9Share( | |||
| _In_ PCWSTR AccessName, _In_ PCWSTR Path, [[maybe_unused]] _In_ UINT32 Port, _In_ hcs::Plan9ShareFlags Flags, _In_ HANDLE UserToken, _In_opt_ PCWSTR VirtIoTag) | |||
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| Scans an option string for one or more transport=<value> tokens, removes | ||
| each from Options, and returns the requested transport. If multiple | ||
| transport= tokens are present, the last one wins. If no transport= | ||
| token is found, the function returns DrvFsTransport::Default and Options | ||
| is left unchanged. If the value is empty or unrecognized, returns | ||
| DrvFsTransport::Invalid. |
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| "mount: transport 'virtiofs' is not available; ensure [wsl2] experimental.drvFsTransports=true is set in " | ||
| ".wslconfig\n"); |
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| "mount: transport 'virtio9p' is not available; ensure [wsl2] experimental.drvFsTransports=true is set in " | ||
| ".wslconfig\n"); |
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| Accepted values are `plan9`, `virtio9p`, and `virtiofs` — matching the corresponding `.wslconfig` setting names. Unknown or empty values cause the mount to fail with an error. | ||
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| The requested transport must be available in the VM. By default the host only stands up the transport selected by `wsl2.virtio9p` / `wsl2.virtiofs`, so mounting with a `transport=` value whose backend is not running fails at mount time. To make all three transports available simultaneously in a single VM (useful for development and benchmarking), enable the experimental setting below. |
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…arking Add the ability to explicitly select which DrvFs transport to use on a per-mount basis via the transport= mount option. This makes it easy to benchmark and compare all three cross-OS filesystem architectures (plan9-over-hvsocket, virtio-9p, and virtiofs) side-by-side in a single VM without reconfiguring .wslconfig between runs. New mount option: mount -t drvfs C: /mnt/c -o transport=plan9 mount -t drvfs C: /mnt/c -o transport=virtio9p mount -t drvfs C: /mnt/c -o transport=virtiofs New host setting: [wsl2] experimental.drvFsTransports=true When drvFsTransports is enabled, the WSL service starts all three filesystem backends concurrently, allowing any transport to be selected at mount time. Behavior: - Invalid transport values fail the mount with a clear error message - Requesting a transport whose backend isn't running fails with an actionable message pointing to the config setting - Standard Linux 'last wins' semantics for duplicate options - No fallback: explicit transport requests never silently degrade Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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| auto result = MountVirtioFs(Source, Target, EffectiveOptions, Admin, Config, ExitCode, false); | ||
| if (result < 0) | ||
| { | ||
| fprintf(stderr, "mount: transport 'virtiofs' is not available\n"); | ||
| } | ||
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| auto result = MountPlan9(Source, Target, EffectiveOptions, Admin, Config, ExitCode, Transport); | ||
| if (result < 0 && Transport == DrvFsTransport::Virtio9p) | ||
| { | ||
| fprintf(stderr, "mount: transport 'virtio9p' is not available\n"); | ||
| } | ||
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Summary
Adds a per-mount
transport=option tomount.drvfsso all three cross-OS filesystem architectures can be benchmarked side-by-side in a single VM without reconfiguring.wslconfigbetween runs.What this enables
With
[wsl2] experimental.drvFsTransports=truein.wslconfig, the WSL service starts all three filesystem backends concurrently. You can then mount the same drive using different transports simultaneously:This makes it trivial to run comparative filesystem benchmarks (fio, compilebench, git operations, etc.) across plan9-over-hvsocket, virtio-9p, and virtiofs without rebooting or restarting WSL.
Behavior
Changes
src/linux/init/drvfs.cpp): Parsetransport=from mount options, dispatch to the requested backend, fail with clear stderr messages on errorWslCoreConfig,WslCoreVm): Newexperimental.drvFsTransportssetting; start all three backends when enableddrvfs.mdwith usage and configurationPR Checklist