submitted as https://github.com/ceph/ceph/pull/40582

--- a/src/common/buffer.cc
+++ b/src/common/buffer.cc
@@ -2268,7 +2268,7 @@

 void ceph::buffer::list::page_aligned_appender::_refill(size_t len) {
   const size_t alloc = \
-    std::max((size_t)min_alloc, (len + CEPH_PAGE_SIZE - 1) & CEPH_PAGE_MASK);
+    std::max(static_cast<size_t>(min_alloc), static_cast<size_t>((len + CEPH_PAGE_SIZE - 1) & CEPH_PAGE_MASK));
   auto new_back = \
     ptr_node::create(buffer::create_page_aligned(alloc));
   new_back->set_length(0);   // unused, so far.