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libstore: Use race-free copyRecursive with makeFSSourceAccessor and RestoreSink when copying FOD outputs

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This commit is contained in:
Sergei Zimmerman
2026-01-10 02:40:48 +03:00
parent 6312a94839
commit 545f5fb309
1 changed files with 11 additions and 3 deletions
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14
src/libstore/unix/build/derivation-builder.cc
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@@ -1703,10 +1703,18 @@ SingleDrvOutputs DerivationBuilderImpl::registerOutputs()
[&](const DerivationOutput::CAFixed & dof) {
auto & wanted = dof.ca.hash;
// Replace the output by a fresh copy of itself to make sure
// that there's no stale file descriptor pointing to it
/* Replace the output by a fresh copy of itself to make sure
that there's no stale file descriptor pointing to it.
IMPORTANT: Copying and deletion must be done in a race-free manner, thus
we are using the source accessor and sink here, since they are implemented
the most robustly. DO NOT USE copyFile here. */
std::filesystem::path tmpOutput = actualPath.native() + ".tmp";
copyFile(actualPath, tmpOutput, true);
auto accessor = makeFSSourceAccessor(actualPath);
auto copySink = RestoreSink(/*startFsync=*/settings.fsyncStorePaths);
copySink.dstPath = tmpOutput;
copyRecursive(*accessor, /*sourcePath=*/CanonPath::root, copySink, /*destPath=*/CanonPath::root);
deletePath(actualPath);
std::filesystem::rename(tmpOutput, actualPath);