8669766a81
The CacheFile.fileLock() method is used to acquire a lock on a cache file so that the file can't be deleted (or its file handle closed) during the execution of a read or a write operation. Today this lock is obtained by first acquiring the eviction lock (the write lock of the readwrite lock), then by checking if the cache file is evicted and the file channel still open, and finally by obtaining the file lock (the read lock of the readwrite lock). Acquiring the read lock while the eviction lock is held ensures that the cache file eviction cannot start in the meanwhile. But eviction starts (and terminations) also acquire the eviction lock; and this lock cannot be obtained while a read lock is held (the write lock of a readwrite lock is exclusive). If we were acquiring a read lock and checking the eviction flag and file channel existence while holding the read lock we know that no eviction can start or finish until the read lock is released. |
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