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ERROR_FILE_SYSTEM_VIRTUALIZATION_BUSY
The projected file-system provider cannot service another request yet
ProjFS invokes provider callbacks for operations such as enumeration, placeholder information, file-data retrieval, and notifications. Providers may complete callbacks asynchronously, but they still need bounded queues and timely completion. This status indicates capacity or concurrency pressure rather than an invalid path or corrupt placeholder.
Measure outstanding callback count, callback latency, backing-store response time, and thread-pool saturation. A provider that performs blocking network or database work directly on callback threads can exhaust its ability to answer new operations. Apply backpressure and asynchronous completion deliberately; repeated immediate retries from callers can amplify the queue. Also check whether a view update or shutdown operation is holding provider-wide state.
What to inspect
- Count pending callbacks and their oldest completion time.
- Move slow backing-store work off callback threads.
- Use bounded retries with delay instead of tight retry loops.
References
- Microsoft: ProjFS programming guide
- Microsoft: virtualization instance lifecycle
- Microsoft: ProjFS directory enumeration
- Microsoft: ProjFS view and cache changes
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