Fix non-atomic reads in PDisk quota calculation

[serbel324]

Changelog entry

Read atomic variables in PDisk QuotaTracker with a proper method.
Fixes #31995

Changelog category

• Bugfix

[ydbot]

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[github-actions]

⚪ 2026-01-16 10:13:24 UTC Pre-commit check linux-x86_64-relwithdebinfo for 13d8b8e has started.
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[Copilot]

Pull request overview

This PR fixes thread safety issues in PDisk quota calculation by ensuring atomic reads of shared variables and preventing division by zero.

Changes:

• Added AtomicGet() calls for HardLimit and Free fields in the Print() method to ensure thread-safe reads
• Modified EstimateSpaceColor() to read HardLimit atomically into a local variable and check for zero before division

---

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[Copilot]

Lines 154-158 compute the occupancy value, but line 160 unconditionally overwrites it, making the preceding calculation dead code. Either remove lines 154-158 or remove line 160. If keeping line 160, note that it lacks the std::max protection from line 155 which prevents negative numerators when newFree exceeds hardLimit.

Suggested change

*occupancy = hardLimit ? (double)(hardLimit - newFree) / hardLimit : 1.0;

[github-actions]

🟢 2026-01-16 10:24:16 UTC The validation of the Pull Request description is successful.

[github-actions]

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⚪ 2026-01-16 10:17:58 UTC ya make is running...
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[github-actions]

⚪ 2026-01-16 10:24:28 UTC Pre-commit check linux-x86_64-relwithdebinfo for f83d4f9 has started.
⚪ 2026-01-16 10:24:45 UTC Artifacts will be uploaded here
⚪ 2026-01-16 10:26:59 UTC ya make is running...
🟡 2026-01-16 12:20:15 UTC Some tests failed, follow the links below. Going to retry failed tests...

Details

Ya make output | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
45395	42320	0	9	3033	33

⚪ 2026-01-16 12:20:33 UTC ya make is running... (failed tests rerun, try 2)
🟡 2026-01-16 12:25:48 UTC Some tests failed, follow the links below. Going to retry failed tests...

Details

Ya make output | Test bloat | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
464 (only retried tests)	450	0	1	0	13

⚪ 2026-01-16 12:25:55 UTC ya make is running... (failed tests rerun, try 3)
🔴 2026-01-16 12:33:16 UTC Some tests failed, follow the links below.

Ya make output | Test bloat | Test bloat | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
146 (only retried tests)	135	0	1	0	10

🟢 2026-01-16 12:33:23 UTC Build successful.
🟢 2026-01-16 12:33:48 UTC ydbd size 2.3 GiB changed* by +736 Bytes, which is < 100.0 KiB vs main: OK

ydbd size dash	main: 491ea35	merge: f83d4f9	diff	diff %
ydbd size	2 503 402 864 Bytes	2 503 403 600 Bytes	+736 Bytes	+0.000%
ydbd stripped size	532 048 328 Bytes	532 048 392 Bytes	+64 Bytes	+0.000%

^{*please be aware that the difference is based on comparing your commit and the last completed build from the post-commit, check comparation}

[github-actions]

⚪ 2026-01-16 10:26:10 UTC Pre-commit check linux-x86_64-release-asan for f83d4f9 has started.
⚪ 2026-01-16 10:26:28 UTC Artifacts will be uploaded here
⚪ 2026-01-16 10:28:36 UTC ya make is running...
🟡 2026-01-16 11:37:07 UTC Some tests failed, follow the links below. This fail is not in blocking policy yet

Ya make output | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
14753	14652	0	63	9	29

🟢 2026-01-16 11:37:21 UTC Build successful.
🟢 2026-01-16 11:37:51 UTC ydbd size 3.8 GiB changed* by -3.2 KiB, which is <= 0 Bytes vs main: OK

ydbd size dash	main: 64b5345	merge: f83d4f9	diff	diff %
ydbd size	4 115 960 488 Bytes	4 115 957 192 Bytes	-3.2 KiB	-0.000%
ydbd stripped size	1 540 010 352 Bytes	1 540 009 712 Bytes	-640 Bytes	-0.000%

^{*please be aware that the difference is based on comparing your commit and the last completed build from the post-commit, check comparation}

[ydbot]

Backport

To backport this PR, click the button next to the target branch and then click "Run workflow" in the Run Actions UI.

Branch	Run
stable-25-3, stable-25-3-1, stable-25-4, stable-25-4-1
stable-25-4, stable-25-4-1
stable-25-4

[ydbot]

Backport results:

• stable-25-4: PR [Backport stable-25-4] PR #32206: Fix non-atomic reads in PDisk quota calculation #32354
• stable-25-4-1: PR [Backport stable-25-4-1] PR #32206: Fix non-atomic reads in PDisk quota calculation #32355

workflow run