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## Problem close https://github.com/neondatabase/neon/issues/10482 ## Summary of changes Add an extra lock on the read path to protect against races. The read path has an implication that only certain kind of compactions can be performed. Garbage keys must first have an image layer covering the range, and then being gc-ed -- they cannot be done in one operation. An alternative to fix this is to move the layers read guard to be acquired at the beginning of `get_vectored_reconstruct_data_timeline`, but that was intentionally optimized out and I don't want to regress. The race is not limited to image layers. Gc-compaction will consolidate deltas automatically and produce a flat delta layer (i.e., when we have retain_lsns below the gc-horizon). The same race would also cause behaviors like getting an un-replayable key history as in https://github.com/neondatabase/neon/issues/10049. Signed-off-by: Alex Chi Z <chi@neon.tech>