From 8e27ee9220883cf5a0629c752e1642daaba4ce14 Mon Sep 17 00:00:00 2001 From: Patrick Steinhardt Date: Sun, 22 Dec 2024 08:24:28 +0100 Subject: [PATCH] reftable/stack: don't perform auto-compaction with less than two tables In order to compact tables we need at least two tables. Bail out early from `reftable_stack_auto_compact()` in case we have less than two tables. In the original, `stack_table_sizes_for_compaction()` yields an array that has the same length as the number of tables. This array is then passed on to `suggest_compaction_segment()`, which returns an empty segment in case we have less than two tables. The segment is then passed to `segment_size()`, which will return `0` because both start and end of the segment are `0`. And because we only call `stack_compact_range()` in case we have a positive segment size we don't perform auto-compaction at all. Consequently, this change does not result in a user-visible change in behaviour when called with a single table. But when called with no tables this protects us against a potential out-of-memory error: `stack_table_sizes_for_compaction()` would try to allocate a zero-byte object when there aren't any tables, and that may lead to a `NULL` pointer on some platforms like NonStop which causes us to bail out with an out-of-memory error. Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano --- reftable/stack.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/reftable/stack.c b/reftable/stack.c index 63976e5ceae489..ae274cd51c8641 100644 --- a/reftable/stack.c +++ b/reftable/stack.c @@ -1552,6 +1552,9 @@ int reftable_stack_auto_compact(struct reftable_stack *st) struct segment seg; uint64_t *sizes; + if (st->merged->readers_len < 2) + return 0; + sizes = stack_table_sizes_for_compaction(st); if (!sizes) return REFTABLE_OUT_OF_MEMORY_ERROR;