[bug fix] Kernel list cache remove directory operation fails when files are created on GCS

[ashmeenkaur]

Description

Scenario:

1. Read directory (listing) with kernel list cache enabled
2. List response is cached in kernel.
3. Create a file on the same GCS bucket inside the same directory outside of the GCSFuse mount via another tool like pantheon, gsutil.
4. call os.RemoveAll on the same directory in GCS Fuse.
5. Kernel will use the list cache response to list & delete the files and the newly created file (outside GCSFuse mount) won't be deleted.
6. os.RemoveAll will fail with directory not empty error when trying to delete the parent directory.

Fix:

1. As part of the RmDir call, we will invalidate the cache by setting the previous directory listing timestamp to 0.
2. This will make the open dir call to invalidate the cache so os.RemoveAll will start working.

Note: even after this fix, rm -r from terminal continues to fail as there in that case, we don't get first RmDir call (which invalidates the cache). Ref:

gcsfuse/internal/fs/fs.go

Line 1752 in 8d72ea9

// When rm -r or os.RemoveAll call is made, the following calls are made in order

Link to the issue in case of a bug fix.

NA

Testing details

1. Manual - NA
2. Unit tests - Added
3. Integration tests - Added

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 71.28%. Comparing base (96d844b) to head (9e32d09).

Files	Patch %	Lines
internal/fs/inode/base_dir.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2163      +/-   ##
==========================================
+ Coverage   71.24%   71.28%   +0.03%     
==========================================
  Files         104      104              
  Lines       11404    11409       +5     
==========================================
+ Hits         8125     8133       +8     
+ Misses       2942     2940       -2     
+ Partials      337      336       -1     

Flag	Coverage Δ
unittests	71.28% <80.00%> (+0.03%)	⬆️

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[raj-prince]

LGTM, few minor comments.