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fix(cache): cap actualEvict by totalUsed_ to prevent eviction deadloop #400

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fix(cache): cap actualEvict by totalUsed_ to prevent eviction deadloop #400

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fix(cache): cap actualEvict by totalUsed_ to prevent eviction deadloop
yuchen0cc Apr 24, 2026
92a6f0e
use audit instead of info
yuchen0cc Apr 27, 2026
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10 changes: 9 additions & 1 deletion src/overlaybd/cache/full_file_cache/cache_pool.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -203,13 +203,21 @@ void FileCachePool::eviction() {
evictByCache = totalUsed_ - waterMark_;
}

auto actualEvict = static_cast<int64_t>(std::max(evictByCache, evictByDisk));
auto actualEvict = std::min(
static_cast<int64_t>(std::max(evictByCache, evictByDisk)),
totalUsed_
);
Comment on lines +206 to +209
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Copilot AI Apr 24, 2026

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The new behavior (capping actualEvict by totalUsed_) fixes a previously-reported infinite-loop scenario; please add a regression test to prevent reintroduction. There are existing gtest-based cache tests under src/overlaybd/cache/test/; consider adding a case that forces evictByDisk > totalUsed_ (e.g., via an IFileSystem wrapper that overrides statvfs) and verifies FileCachePool::eviction() terminates even when the LRU contains entries with openCount > 0 and size == 0.

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if (actualEvict <= 0) {
return;
}

isFull_ = true;

if (!lru_.empty() && !exit_) {
LOG_AUDIT("eviction", VALUE(actualEvict), VALUE(evictByCache), VALUE(evictByDisk), VALUE(totalUsed_));
}

while (actualEvict > 0 && !lru_.empty() && !exit_) {
auto fileIter = lru_.back();
const auto &fileName = fileIter->first;
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