fix fused_set_kv_buffer for rope with Ling-v2 (#20316)

python/sglang/srt/models/bailing_moe.py

@@ -532,6 +532,10 @@ class BailingMoEAttention(nn.Module):
                 head_dim=self.head_dim,
                 alt_stream=self.alt_stream,
             )
+        can_fuse_set_kv = (
+            self.head_dim == self.rotary_emb.rotary_dim
+            and enable_fused_set_kv_buffer(forward_batch)
+        )
         q, k = self.rotary_emb(
             positions,
             q,
@@ -542,7 +546,7 @@ class BailingMoEAttention(nn.Module):
                     layer=self.attn,
                     forward_batch=forward_batch,
                 )
-                if enable_fused_set_kv_buffer(forward_batch)
+                if can_fuse_set_kv
                 else None
             ),
         )
@@ -551,7 +555,7 @@ class BailingMoEAttention(nn.Module):
             k,
             v,
             forward_batch,
-            save_kv_cache=not enable_fused_set_kv_buffer(forward_batch),
+            save_kv_cache=not can_fuse_set_kv,
         )
         attn_output, _ = self.dense(context_layer)
         return attn_output