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a9cb3971c6
When reloading large hosts files (e.g. 1.7M addn-hosts entries) on SIGHUP, free_names() previously only reset block->last = 0 without unlinking or moving blocks to a spare pool. As a result, all existing blocks remained in hostblocks. When reloading, the head block was filled first and stayed at the head while full, forcing store_name() to linearly traverse all previously filled blocks for every subsequent name insertion. This resulted in O(N^2) complexity, taking ~10 minutes for 1.7M records. Fix this by introducing nameblock_spare (matching config_spare / big_free spare pool semantics), moving freed blocks to the spare pool in free_names(), and restricting store_name() to only check the active head block before popping from nameblock_spare (or mallocing). This restores O(1) per-entry insertion and reduces reload time from 10 minutes to ~3 seconds.