crush: fix fast rule lookup when uniform

Older clients will search for the first rule with a matching ruleset,
type, and size.  The has_uniform_rules bool is only set if we have rule
ids and rulesets that line up, but we must also verify that the rest of the
mask matches or else we can get a different CRUSH mapping result because
the mask might not match and old clients will fail to find a rule and we
will find one.  We also can't just check the ruleset as the legacy clients
find the *first* (of potentially many) matching rules; hence we only do
the fast check if all rulesets == rule id.

Signed-off-by: Sage Weil <sage@redhat.com>

diff --git a/src/crush/CrushWrapper.h b/src/crush/CrushWrapper.h
index cefcd8fee17f3e584bd1d5c3793715afad6eeb0b..a8c017c29c5bbee7638323d12819f71b1301e979 100644 (file)
--- a/src/crush/CrushWrapper.h
+++ b/src/crush/CrushWrapper.h
@@ -1261,14 +1261,15 @@ public:
 
   int find_rule(int ruleset, int type, int size) const {
     if (!crush) return -1;
-    if (!have_uniform_rules) {
-      return crush_find_rule(crush, ruleset, type, size);
-    } else {
-      if (ruleset < (int)crush->max_rules &&
-         crush->rules[ruleset])
-       return ruleset;
-      return -1;
+    if (have_uniform_rules &&
+       ruleset < (int)crush->max_rules &&
+       crush->rules[ruleset] &&
+       crush->rules[ruleset]->mask.type == type &&
+       crush->rules[ruleset]->mask.min_size <= size &&
+       crush->rules[ruleset]->mask.max_size >= size) {
+      return ruleset;
     }
+    return crush_find_rule(crush, ruleset, type, size);
   }
 
   bool ruleset_exists(const int ruleset) const {