backport: partial Merge bitcoin/bitcoin#26326: net: reduce LOCK(cs_main) scope in GETBLOCKTXN by thepastaclaw · Pull Request #7350 · dashpay/dash

thepastaclaw · 2026-06-09T01:03:09Z

backport: partial Merge bitcoin#26326

Upstream backport

This PR is a partial backport of bitcoin#26326:

Upstream PR: net: don't lock cs_main while reading blocks in net processing bitcoin/bitcoin#26326
Backported commit: bitcoin/bitcoin@613a45c (net: reduce LOCK(cs_main) scope in GETBLOCKTXN)
Not included here: the sibling upstream ProcessGetBlockData commit from the same Bitcoin PR.

Issue being fixed or feature implemented

Recent GETBLOCKTXN handling selected and read the requested block from disk while holding cs_main. A peer can request recent block transactions repeatedly, so the disk I/O should not extend the validation/global chain lock hold time.

What was done?

Capture the recent block's disk position while holding cs_main.
Release cs_main before reading the block from disk.
Verify the read block hash still matches the requested block hash before sending BLOCKTXN.
Treat a missing, pruned, or mismatched read defensively by logging and returning instead of asserting.

How Has This Been Tested?

Tested on macOS arm64.

git diff --check upstream/develop...HEAD
./configure --without-gui --disable-bench --disable-fuzz-binary with the macOS arm64 depends config.site
make -j8 src/dashd
Pre-PR code review gate: ship

After converting the PR history to backport metadata, the source tree stayed unchanged from the previously reviewed/rebased head.

Breaking Changes

None.

Checklist

I have performed a self-review of my own code
I have commented my code, particularly in hard-to-understand areas
I have added or updated relevant unit/integration/functional/e2e tests
I have made corresponding changes to the documentation
I have assigned this pull request to a milestone

thepastaclaw · 2026-06-09T01:03:25Z

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coderabbitai · 2026-06-09T01:03:31Z

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Review finished.

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coderabbitai · 2026-06-09T01:07:30Z

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 792ed148-9daf-46b0-8df6-d2fca9970dc2

📥 Commits

Reviewing files that changed from the base of the PR and between c6ccbc6 and 037d040.

📒 Files selected for processing (1)

src/net_processing.cpp

🚧 Files skipped from review as they are similar to previous changes (1)

src/net_processing.cpp

Walkthrough

This PR adds a compile-time check that MAX_BLOCKTXN_DEPTH does not exceed MIN_BLOCKS_TO_KEEP. It also updates GETBLOCKTXN handling to read deep blocks from the stored disk position, verify the returned hash matches the requested block hash, and only then send BLOCKTXN.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Suggested reviewers

UdjinM6
PastaPastaPasta

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly matches the main change: a partial backport reducing LOCK(cs_main) scope in GETBLOCKTXN.
Description check	✅ Passed	The description is directly about the same backport and accurately summarizes the implemented changes and testing.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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github-actions · 2026-06-09T01:18:48Z

✅ No Merge Conflicts Detected

This PR currently has no conflicts with other open PRs.

thepastaclaw · 2026-06-09T04:52:17Z

✅ Review complete (commit 037d040)

thepastaclaw

Code Review

Targeted change narrows the cs_main hold window in GETBLOCKTXN by capturing the block file position under the lock and performing the disk read outside it, with a hash check that fails closed on stale/pruned/mismatched reads. Both agents concur the change is correct; only a minor log-granularity nitpick remains.

💬 1 nitpick(s)

thepastaclaw · 2026-06-09T05:05:38Z

+            if (!hash || *hash != req.blockhash) {
+                LogPrint(BCLog::NET, "Peer %d sent us a getblocktxn for a block we could not read\n", pfrom.GetId());
                return;


💬 Nitpick: Log message conflates I/O failure with hash mismatch

After dropping cs_main, the failure path emits the same "a block we could not read" line for two distinct conditions: ReadBlockFromDisk returning nullopt (open/deserialize/PoW failure) and the read succeeding with *hash != req.blockhash (a stale FlatFilePos / disk-state inconsistency after the lock was released). Distinguishing these helps operators tell transient I/O or pruning issues from a position-vs-hash race. Diagnostic quality only; not a defect.

_{source: ['claude']}

PastaPastaPasta · 2026-06-15T12:23:06Z

Is this not code we inherited from bitcoin? it is rare we want to accept a "fix" in their code.

thepastaclaw · 2026-06-15T13:10:27Z

Good question. I checked this against upstream Bitcoin: the change is actually bringing this path back in line with the current inherited Bitcoin pattern, not inventing a Dash-only behavior.

Bitcoin master already copies the recent block position under cs_main, releases the lock, then reads the block from disk outside cs_main and serves BLOCKTXN. This PR does the same for Dash, with the Dash-local ReadBlockFromDisk API/hash check shape.

So I agree with the general rule — we should be cautious about “fixing” inherited Bitcoin code — but in this case the safer path is to follow the upstream Bitcoin fix rather than keep Dash on the older wider-lock version.

PastaPastaPasta · 2026-06-17T07:13:18Z

@thepastaclaw

Bitcoin master already copies the recent block position under cs_main, releases the lock, then reads the block from disk outside cs_main and serves BLOCKTXN. This PR does the same for Dash, with the Dash-local ReadBlockFromDisk API/hash check shape.

Hmm; it seems then, that there may be a backport that we should backport instead of doing this adhoc?

thepastaclaw · 2026-06-17T07:46:17Z

Yep — I traced it more precisely and there is an exact upstream Bitcoin commit for this:

bitcoin/bitcoin@613a45c — net: reduce LOCK(cs_main) scope in GETBLOCKTXN

That commit adds the same MAX_BLOCKTXN_DEPTH <= MIN_BLOCKS_TO_KEEP assertion and moves the GETBLOCKTXN disk read out from under cs_main. This PR is effectively that backport adapted to Dash's current ReadBlockFromDisk shape / block hash validation.

So I agree with your process concern: this should be treated as a Bitcoin backport, not as an ad-hoc Dash-only fix. If you prefer, I can close this PR and re-run it through the normal backport flow; otherwise I can update the PR metadata/commit message to explicitly cite the upstream commit.

github-actions · 2026-06-27T11:41:26Z

This pull request has conflicts, please rebase.

github-actions · 2026-06-27T12:04:49Z

This pull request has conflicts, please rebase.

thepastaclaw · 2026-06-27T12:06:11Z

Rebased this onto current develop and pushed c6ccbc6. GitHub now reports the PR branch as mergeable and predict_conflicts passed. The remaining check_merge failure is the repository-level master/develop fast-forward check, not a conflict in this PR branch.

thepastaclaw

Code Review

Cumulative review at c6ccbc6: the GETBLOCKTXN lock-scope reduction is correct — FlatFilePos is captured under cs_main, disk I/O runs lock-free, and the post-read hash check fails closed on stale/mismatched reads. No new in-scope defects in the latest delta. Carrying forward the prior nitpick about the log message conflating read failure with hash mismatch (already tracked in an unresolved inline thread).

💬 1 nitpick(s)

Note: GitHub does not allow me to submit APPROVE on my own PR, so this is posted as a COMMENT while preserving the verified non-blocking findings.

thepastaclaw · 2026-06-27T12:19:47Z

+            if (!hash || *hash != req.blockhash) {
+                LogPrint(BCLog::NET, "Peer %d sent us a getblocktxn for a block we could not read\n", pfrom.GetId());
                return;


💬 Nitpick: Log line conflates disk read failure with hash mismatch

After cs_main is released, two operationally distinct failures share one log line: ReadBlockFromDisk returning std::nullopt (OpenBlockFile failure, deserialization error, PoW header check failure — typically pruning or corruption) and a successful read whose *hash != req.blockhash (the FlatFilePos captured under cs_main no longer points at the requested block, e.g. a race with reorg/prune/reindex in the very window this PR introduces). Splitting these into two messages would make the new lock-scope reduction easier to diagnose if it surfaces in the wild. Purely diagnostic quality; behavior is correct. Existing unresolved thread: #7350 (comment).

_{source: ['claude', 'codex']}

PastaPastaPasta · 2026-06-27T12:26:18Z

Claw; please update this to actually be a backport, if it should so be instead of an adhoc change that doesn't accomplish / get shown in history as a backport

…OCKTXN 613a45c net: reduce LOCK(cs_main) scope in GETBLOCKTXN (Andrew Toth) Pull request description: Inspired by bitcoin#11913 and bitcoin#26308. `cs_main` doesn't need to be locked while reading blocks. This removes the locks in `net_processing`. Dash notes: This is a partial backport of bitcoin#26326. It includes only the GETBLOCKTXN commit, adapted to Dash's current ReadBlockFromDisk API and post-read hash validation. The sibling upstream ProcessGetBlockData commit is not included in this PR.

thepastaclaw · 2026-06-27T14:03:54Z

Updated. I amended the PR head so the commit history now records this as a partial backport of bitcoin#26326, specifically bitcoin/bitcoin@613a45c (net: reduce LOCK(cs_main) scope in GETBLOCKTXN). I also updated the PR title/body to make the backport source explicit. The tree is unchanged from the previously reviewed/rebased head; this push is metadata/history only.

thepastaclaw

Code Review

Cumulative review at 037d040. Source tree is unchanged from c6ccbc6; the push only rewrote commit metadata into proper Dash partial-backport form. The GETBLOCKTXN lock-scope reduction is correct: FlatFilePos captured under cs_main, disk read runs lock-free, post-read hash check fails closed on mismatch/missing/pruned. Only carried-forward finding is a low-confidence log-diagnostic nitpick about line 4496 conflating two distinct failure modes.

💬 1 nitpick(s)

Carried-forward findings already raised (1)

These findings were not re-posted as new inline comments because an existing review thread already covers them.

[NITPICK] (deduped existing open thread) src/net_processing.cpp:4495-4497: Log message conflates I/O failure with hash mismatch — Two operationally distinct failures share one log message: ReadBlockFromDisk returning std::nullopt (OpenBlockFile failure, deserialization error, PoW header check failure — typically pruning/corruption) and a successful read whose *hash != req.blockhash (the FlatFilePos captured under cs_m...

Note: GitHub does not allow me to approve my own PR, so this is posted as a COMMENT while preserving the verified nonblocking finding.

thepastaclaw force-pushed the fix/getblocktxn-recent-disk-read branch from 6440dea to 97af883 Compare June 9, 2026 02:38

thepastaclaw marked this pull request as ready for review June 9, 2026 04:52

thepastaclaw commented Jun 9, 2026

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github-actions Bot mentioned this pull request Jun 25, 2026

backport: merge bitcoin/bitcoin#25144: refactor: Pass Peer& to Misbehaving() #7331

Merged

5 tasks

github-actions Bot added the needs rebase label Jun 27, 2026

thepastaclaw force-pushed the fix/getblocktxn-recent-disk-read branch from 97af883 to c6ccbc6 Compare June 27, 2026 12:04

github-actions Bot added needs rebase and removed needs rebase labels Jun 27, 2026

thepastaclaw commented Jun 27, 2026

View reviewed changes

github-actions Bot removed the needs rebase label Jun 27, 2026

thepastaclaw force-pushed the fix/getblocktxn-recent-disk-read branch from c6ccbc6 to 037d040 Compare June 27, 2026 14:03

thepastaclaw changed the title ~~fix: reduce GETBLOCKTXN disk read lock scope~~ backport: partial Merge bitcoin/bitcoin#26326: net: reduce LOCK(cs_main) scope in GETBLOCKTXN Jun 27, 2026

thepastaclaw commented Jun 27, 2026

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backport: partial Merge bitcoin#26326

Upstream backport

Issue being fixed or feature implemented

What was done?

How Has This Been Tested?

Breaking Changes

Checklist

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Walkthrough

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Suggested reviewers

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