common/options/crimson.yaml.in: add hot_tier_generations minimum

See ExtentPlacementManager::init

dynamic_max_rewrite_generation = hot_tier_generations - 1;
ceph_assert(dynamic_max_rewrite_generation > MIN_REWRITE_GENERATION);

Signed-off-by: Matan Breizman <[email protected]>

Author: Matan-B

src/common/options/crimson.yaml.in

@@ -231,6 +231,7 @@ options:
   level: advanced
   desc: The number of generations in the hot tier or the whole SeaStore instance if there's only one tier.
   default: 5
+  min: 5
 - name: seastore_cold_tier_generations
   type: uint
   level: advanced

src/crimson/os/seastore/extent_placement_manager.cc

@@ -203,7 +203,6 @@ void ExtentPlacementManager::init(
         "hot_tier_generations{} , cold_tier_generations {}",
         dynamic_max_rewrite_generation, hot_tier_generations,
         cold_tier_generations);
-  // TODO: hot_tier_generations should have a minumum..
   ceph_assert(dynamic_max_rewrite_generation > MIN_REWRITE_GENERATION);
 
   if (trimmer->get_backend_type() == backend_type_t::SEGMENTED) {