Crush: Ensuring at most num-rep osds are selected

Crush temporary buffers are allocated as per replica size configured
by the user.When there are more final osds (to be selected as per
rule) than the replicas, buffer overlaps and it causes crash.Now, it
ensures that at most num-rep osds are selected even if more number of
osds are allowed by indep rule. The fix for firstn rules is already
merged as part of bug #9492. Required test files are added.

Fixes: #9492

Signed-off-by: Johnu George johnugeo@cisco.com

src/crush/mapper.c

@@ -690,6 +690,7 @@ int crush_do_rule(const struct crush_map *map,
 	__u32 step;
 	int i, j;
 	int numrep;
+	int out_size;
 	/*
 	 * the original choose_total_tries value was off by one (it
 	 * counted "retries" and not "tries").  add one.
@@ -807,11 +808,13 @@ int crush_do_rule(const struct crush_map *map,
 						c+osize,
 						0);
 				} else {
+					out_size = ((numrep < (result_max-osize)) ?
+                                                    numrep : (result_max-osize));
 					crush_choose_indep(
 						map,
 						map->buckets[-1-w[i]],
 						weight, weight_max,
-						x, numrep, numrep,
+						x, out_size, numrep,
 						curstep->arg2,
 						o+osize, j,
 						choose_tries,
@@ -820,7 +823,7 @@ int crush_do_rule(const struct crush_map *map,
 						recurse_to_leaf,
 						c+osize,
 						0);
-					osize += numrep;
+					osize += out_size;
 				}
 			}
 

src/test/cli/crushtool/test-map-firstn-indep.t

@@ -0,0 +1,14 @@
+  $ crushtool -c "$TESTDIR/test-map-firstn-indep.txt" -o "$TESTDIR/test-map-firstn-indep.crushmap"
+  $ crushtool -i "$TESTDIR/test-map-firstn-indep.crushmap" --test --rule 0 --x 1 --show-bad-mappings
+  bad mapping rule 0 x 1 num_rep 9 result [93,80,88,87,56,50,53,72]
+  bad mapping rule 0 x 1 num_rep 10 result [93,80,88,87,56,50,53,72]
+  $ crushtool -i "$TESTDIR/test-map-firstn-indep.crushmap" --test --rule 1 --x 1 --show-bad-mappings
+  bad mapping rule 1 x 1 num_rep 3 result [93,56]
+  bad mapping rule 1 x 1 num_rep 4 result [93,56]
+  bad mapping rule 1 x 1 num_rep 5 result [93,56]
+  bad mapping rule 1 x 1 num_rep 6 result [93,56]
+  bad mapping rule 1 x 1 num_rep 7 result [93,56]
+  bad mapping rule 1 x 1 num_rep 8 result [93,56]
+  bad mapping rule 1 x 1 num_rep 9 result [93,56]
+  bad mapping rule 1 x 1 num_rep 10 result [93,56]
+  $ rm -f "$TESTDIR/test-map-firstn-indep.crushmap"