df(windows): fix Avail/Use% by using number_of_free_clusters for bavail

[naoNao89]

Fix Windows df incorrectly reporting 0 bytes available and 100% usage for all filesystems. The issue was caused by hardcoding bavail (blocks available to non-privileged processes) to 0 instead of using the actual free clusters from Windows API.

On Windows, all mounted filesystems displayed:

• Avail: 0 bytes (always)
• Use%: 100% (always)
• --total flag: Completely broken aggregation

This made df output useless for Windows users.

Before (Broken)

Filesystem               Size  Used Avail Use%
\Device\HarddiskVolume2  256G  180G     0 100%
\Device\HarddiskVolume3  677G  494G     0 100%
\Device\HarddiskVolume4  1.9T  1.8T     0 100%
\Device\HarddiskVolume1   50M   35M     0 100%
\Device\HarddiskVolume8   11T  5.9T     0 100%

After (Fixed)

Filesystem               Size  Used Avail Use%
\Device\HarddiskVolume2  256G  180G  76G  70%
\Device\HarddiskVolume3  677G  494G 183G  73%
\Device\HarddiskVolume4  1.9T  1.8T 100G  95%
\Device\HarddiskVolume1   50M   35M  15M  70%
\Device\HarddiskVolume8   11T  5.9T 5.1T  54%

Windows API Context

The fix correctly implements POSIX semantics on Windows:

POSIX	Windows	Meaning
f_bfree	lpNumberOfFreeClusters (no quota consideration)	Total free clusters
f_bavail	lpNumberOfFreeClusters (quota-aware)	Free clusters available to user

Windows GetDiskFreeSpaceW() already respects disk quotas, making this fix semantically correct.

Fixes

Closes #7461

Related Issues

• test_file_column_width_if_filename_contains_unicode_chars started to fail recently #5015: df tests failing on Windows (tests were disabled) - can now be re-enabled
• df: Fix overflow error on WSL. Default to 0 when the values are non-sense. #5381: df overflow error on WSL (fixed) - works better with correct bavail

[github-actions]

GNU testsuite comparison:

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[sylvestre]

could you please add a test to make sure we don't regress in the future? thanks

[naoNao89]

done assert!(fs_usage.bavail >= 0);

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/misc/tee (fails in this run but passes in the 'main' branch)

[sylvestre]

@naoNao89 i was thinking about tests/by-util/test_df.rs

[codspeed-hq]

Merging this PR will not alter performance

✅ 288 untouched benchmarks
⏩ 38 skipped benchmarks¹

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_{Comparing naoNao89:fix/df-windows-bavail (37f3d7a) with main (e7f2fd9)}

Footnotes

1. 38 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/tail/overlay-headers (fails in this run but passes in the 'main' branch)

[github-actions]

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Skipping an intermittent issue tests/tail/overlay-headers (passes in this run but fails in the 'main' branch)

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[github-actions]

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GNU test failed: tests/df/skip-rootfs. tests/df/skip-rootfs is passing on 'main'. Maybe you have to rebase?
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Congrats! The gnu test tests/basenc/bounded-memory is now passing!

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/factor/t10. tests/factor/t10 is passing on 'main'. Maybe you have to rebase?
GNU test failed: tests/factor/t33. tests/factor/t33 is passing on 'main'. Maybe you have to rebase?
GNU test failed: tests/factor/t34. tests/factor/t34 is passing on 'main'. Maybe you have to rebase?
Skip an intermittent issue tests/pr/bounded-memory (fails in this run but passes in the 'main' branch)
Congrats! The gnu test tests/basenc/bounded-memory is now passing!

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/factor/t10. tests/factor/t10 is passing on 'main'. Maybe you have to rebase?
GNU test failed: tests/factor/t33. tests/factor/t33 is passing on 'main'. Maybe you have to rebase?
Skip an intermittent issue tests/pr/bounded-memory (fails in this run but passes in the 'main' branch)
Congrats! The gnu test tests/factor/t32 is no longer failing!
Note: The gnu test tests/cut/bounded-memory is now being skipped but was previously passing.
Note: The gnu test tests/tail/pipe-f is now being skipped but was previously passing.
Congrats! The gnu test tests/basenc/bounded-memory is now passing!

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/factor/t33. tests/factor/t33 is passing on 'main'. Maybe you have to rebase?
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Skip an intermittent issue tests/pr/bounded-memory (fails in this run but passes in the 'main' branch)
Congrats! The gnu test tests/basenc/bounded-memory is now passing!