[Bug Report] cfapi: CreateFileMapping causes full placeholder hydration ignoring CF_HYDRATION_POLICY_PROGRESSIVE

Question

[Bug Report] cfapi: CreateFileMapping causes full placeholder hydration ignoring CF_HYDRATION_POLICY_PROGRESSIVE

Max 1

Hi! My company is on the verge of releasing an update to our Sync Engine implementation with PROGRESSIVE hydration support and we recently found out that its not working properly with file mapping, i.e. any call to CreateFileMapping causes full hydration of a placeholder by the Platform no matter what region is specified and ignoring the fact that no data access has happened yet. Are there any plans to make it work? Thanks

Minimal reproducible sample: https://github.com/Maksim-Isakau/CloudTest/tree/create-file-mapping-report

Cloud sample test!
Succesfully called AddFolderToSearchIndexer on "file:///C:\Users\max\AppData\Local\Temp\cf-9124.tmp-dir"
platform version is 22621.2506.1552
TestSimpleRead: read first 4096 using ReadFile api
OnFetchData from:\Device\HarddiskVolume6\repos\CloudTest\x64\Debug\CloudTest.exe offset:0 len:4096
TestSimpleRead done
TestFileMapping: read first 4096 using CreateFileMapping and MapViewOfFile api
OnFetchData from:\Device\HarddiskVolume6\repos\CloudTest\x64\Debug\CloudTest.exe offset:0 len:134217728
TestFileMapping done

Jeanine Zhang-MSFT 11,356 Reputation points Microsoft External Staff

2024-10-14T05:26:48.78+00:00

Could you please tell us how to reproduce the issue via the sample? Whether could you reproduce the issue via the official sample: Cloud Mirror.
Max 1 Reputation point

2024-10-14T10:00:15.3766667+00:00
repro is here: https://github.com/Maksim-Isakau/CloudTest/tree/create-file-mapping-report

you can't repro it via the official CloudMirror sample as it doesn't support "progressive" hydration. I've made a minimal repro that demonstrates this issue. just launch an app and observe the output.

The code in a repro

registers a custom provider

creates a 128 MB placeholder file

opens a handle to this PH and reads first 4096 bytes of this file. As expected, this triggers FETCH_DATA callback with the same range request

then test does the similar using file mapping api: opens a handle, calls CreateFileMapping and MapViewOfFile. this part behaves differently: upon CreateFileMapping you get FETCH_DATA for the whole 128MB of the file.

An example output is provided in the head of this topic.
Jeanine Zhang-MSFT 11,356 Reputation points Microsoft External Staff

2024-10-15T07:35:06.1+00:00

As this issue is complex, to resolve this issue as soon as possible, you can open an incident via Contact us tab at link below: https://developer.microsoft.com/en-us/windows/support/

Please choose the Technical Support - Coding/Debugging for Windows SDK for this issue. In-addition, if the support engineer determines that the issue is the result of a bug the service request will be a no-charge case and you won't be charged.