BugFix - UploadFileOperation Concurrency

[alperozturk96]

• Tests written, or not not needed

Fixes

#14945 (comment)

10:54:53.066  D  cache_test_DISK_         image read from disk 389741429
10:54:53.067  D  AutoRename               Before - /bbaR/TEST_21 (2).jpg
10:54:53.068  D  AutoRename               After - /bbaR/TEST_21 (2).jpg
10:54:53.068  V  UploadsStorageManager    Updating .../TEST_21 (2).jpg with status:UPLOAD_SUCCEEDED, result:FILE_NOT_FOUND
10:54:53.068  V  UploadsStorageManager    Updating .../TEST_21 (2).jpg with status=UPLOAD_SUCCEEDED
10:54:53.071  D  UploadsStorageManager    updateUpload returns 1 for file: .../TEST_21 (2).jpg
10:54:53.071  D  UploadsStorageManager    notifyObserversNow
10:54:53.071  D  FileUploadWorker         NotifyUploadResult: LOCAL_FILE_NOT_FOUND
10:54:53.073  W  UploadFileOperation      file is null, obtaining from upload

Issue

When uploading large batches of files (≈50 or more), UploadFileOperation is invoked multiple times for the same file. This can cause race conditions where one thread deletes or releases a file reference before another thread attempts to read it, resulting in a LOCAL_FILE_NOT_FOUND error.

How to reproduce?

1. Have a local folder that contains 50 images
2. Setup AutoUpload for that local folder with "move to app folder"
3. Check logs

[github-actions]

Codacy

Lint

Type	master	PR
Warnings	48	49
Errors	11	11

SpotBugs

Category	Base	New
Bad practice	60	60
Correctness	63	65
Dodgy code	296	296
Experimental	1	1
Internationalization	7	7
Malicious code vulnerability	2	2
Multithreaded correctness	35	35
Performance	50	50
Security	18	18
Total	532	534

Lint increased!

SpotBugs increased!

[github-actions]

APK file: https://www.kaminsky.me/nc-dev/android-artifacts/15333.apk



To test this change/fix you can simply download above APK file and install and test it in parallel to your existing Nextcloud app.

[alperozturk96]

For 50 files, 70 UploadFileOperation used.

[alperozturk96]

When I try to catch all errors in move function via same scenario, function didn't throw any error.

Also, even spotbugs warns about multithread correctness @tobiasKaminsky