diff --git a/repos/dde_linux/src/lib/vfs/lxip/vfs.cc b/repos/dde_linux/src/lib/vfs/lxip/vfs.cc
index fa11b12d96..24a66f095e 100644
--- a/repos/dde_linux/src/lib/vfs/lxip/vfs.cc
+++ b/repos/dde_linux/src/lib/vfs/lxip/vfs.cc
@@ -267,7 +267,7 @@ struct Vfs::Lxip_vfs_handle : Vfs::Vfs_handle
 	/**
 	 * Check if the file attached to this handle is ready to read
 	 */
-	virtual bool read_ready() = 0;
+	virtual bool read_ready() const = 0;
 
 	virtual Read_result   read(char *dst,
 	                           file_size count, file_size &out_count) = 0;
@@ -312,7 +312,7 @@ struct Vfs::Lxip_vfs_file_handle final : Vfs::Lxip_vfs_handle
 			file->handles.remove(&file_le);
 	}
 
-	bool read_ready() override {
+	bool read_ready() const override {
 		return (file) ? file->poll() : false; }
 
 	Read_result read(char *dst, file_size count, file_size &out_count) override
@@ -364,7 +364,7 @@ struct Vfs::Lxip_vfs_dir_handle final : Vfs::Lxip_vfs_handle
 	: Vfs::Lxip_vfs_handle(fs, alloc, status_flags),
 	  dir(dir) { }
 
-	bool read_ready() override { return true; }
+	bool read_ready() const override { return true; }
 
 	Read_result read(char *dst, file_size count, file_size &out_count) override
 	{
@@ -1202,7 +1202,7 @@ struct Vfs::Lxip_socket_handle final : Vfs::Lxip_vfs_handle
 			socket_dir(alloc, parent, sock)
 		{ }
 
-		bool read_ready() override { return true; }
+		bool read_ready() const override { return true; }
 
 		Read_result read(char *dst, file_size count, file_size &out_count) override
 		{
@@ -1994,10 +1994,11 @@ class Vfs::Lxip_file_system : public Vfs::File_system,
 			return false;
 		}
 
-		bool read_ready(Vfs_handle *vfs_handle) override
+		bool read_ready(Vfs_handle const &vfs_handle) const override
 		{
-			Lxip_vfs_handle &handle =
-				*static_cast<Lxip_vfs_handle *>(vfs_handle);
+			Lxip_vfs_handle const &handle =
+				static_cast<Lxip_vfs_handle const &>(vfs_handle);
+
 			return handle.read_ready();
 		}
 
diff --git a/repos/dde_rump/src/lib/vfs/rump/vfs_rump.cc b/repos/dde_rump/src/lib/vfs/rump/vfs_rump.cc
index b168fb2d1c..82b5e0c8df 100644
--- a/repos/dde_rump/src/lib/vfs/rump/vfs_rump.cc
+++ b/repos/dde_rump/src/lib/vfs/rump/vfs_rump.cc
@@ -807,8 +807,7 @@ class Vfs::Rump_file_system : public File_system
 			return READ_ERR_INVALID;
 		}
 
-		bool read_ready(Vfs_handle *) override { return true; }
-
+		bool read_ready (Vfs_handle const &) const override { return true; }
 		bool write_ready(Vfs_handle const &) const override { return true; }
 
 		Ftruncate_result ftruncate(Vfs_handle *vfs_handle, file_size len) override
diff --git a/repos/gems/src/lib/vfs/audit/vfs_audit.cc b/repos/gems/src/lib/vfs/audit/vfs_audit.cc
index c58cffd7d3..12c23c6d03 100644
--- a/repos/gems/src/lib/vfs/audit/vfs_audit.cc
+++ b/repos/gems/src/lib/vfs/audit/vfs_audit.cc
@@ -268,16 +268,21 @@ class Vfs_audit::File_system : public Vfs::File_system
 			return result;
 		}
 
-		bool read_ready(Vfs_handle *vfs_handle) override
+		bool read_ready(Vfs_handle const &vfs_handle) const override
 		{
-			Handle &h = *static_cast<Handle*>(vfs_handle);
-			h.sync_state();
-			return h.audit->fs().read_ready(h.audit);
+			Handle const &h = static_cast<Handle const &>(vfs_handle);
+
+			const_cast<Handle &>(h).sync_state();
+
+			return h.audit->fs().read_ready(*h.audit);
 		}
 
 		bool write_ready(Vfs_handle const &vfs_handle) const override
 		{
 			Handle const &h = static_cast<Handle const &>(vfs_handle);
+
+			const_cast<Handle &>(h).sync_state();
+
 			return h.audit->fs().write_ready(*h.audit);
 		}
 
diff --git a/repos/gems/src/lib/vfs/cbe/vfs.cc b/repos/gems/src/lib/vfs/cbe/vfs.cc
index f657ea7ca8..2eff57abd0 100644
--- a/repos/gems/src/lib/vfs/cbe/vfs.cc
+++ b/repos/gems/src/lib/vfs/cbe/vfs.cc
@@ -2020,8 +2020,7 @@ class Vfs_cbe::Data_file_system : public Single_file_system
 				return SYNC_ERR_INVALID;
 			}
 
-			bool read_ready() override { return true; }
-
+			bool read_ready()  const override { return true; }
 			bool write_ready() const override { return true; }
 		};
 
@@ -2191,8 +2190,7 @@ class Vfs_cbe::Extend_file_system : public Vfs::Single_file_system
 				return WRITE_OK;
 			}
 
-			bool read_ready() override { return true; }
-
+			bool read_ready()  const override { return true; }
 			bool write_ready() const override { return true; }
 		};
 
@@ -2376,8 +2374,7 @@ class Vfs_cbe::Rekey_file_system : public Vfs::Single_file_system
 				return WRITE_OK;
 			}
 
-			bool read_ready() override { return true; }
-
+			bool read_ready()  const override { return true; }
 			bool write_ready() const override { return true; }
 		};
 
@@ -2561,8 +2558,7 @@ class Vfs_cbe::Deinitialize_file_system : public Vfs::Single_file_system
 				return WRITE_OK;
 			}
 
-			bool read_ready() override { return true; }
-
+			bool read_ready()  const override { return true; }
 			bool write_ready() const override { return true; }
 		};
 
@@ -2699,8 +2695,7 @@ class Vfs_cbe::Create_snapshot_file_system : public Vfs::Single_file_system
 				return WRITE_OK;
 			}
 
-			bool read_ready() override { return true; }
-
+			bool read_ready()  const override { return true; }
 			bool write_ready() const override { return true; }
 		};
 
@@ -2799,8 +2794,7 @@ class Vfs_cbe::Discard_snapshot_file_system : public Vfs::Single_file_system
 				return WRITE_ERR_IO;
 			}
 
-			bool read_ready() override { return true; }
-
+			bool read_ready()  const override { return true; }
 			bool write_ready() const override { return true; }
 		};
 
@@ -3065,7 +3059,7 @@ class Vfs_cbe::Snapshots_file_system : public Vfs::File_system
 				return SYNC_OK;
 			}
 
-			virtual bool read_ready() = 0;
+			virtual bool read_ready() const = 0;
 		};
 
 
@@ -3159,7 +3153,7 @@ class Vfs_cbe::Snapshots_file_system : public Vfs::File_system
 				return WRITE_ERR_INVALID;
 			}
 
-			bool read_ready() override { return true; }
+			bool read_ready() const override { return true; }
 		};
 
 		struct Dir_snap_vfs_handle : Vfs::Vfs_handle
@@ -3457,7 +3451,7 @@ class Vfs_cbe::Snapshots_file_system : public Vfs::File_system
 			return READ_ERR_IO;
 		}
 
-		bool read_ready(Vfs::Vfs_handle *) override
+		bool read_ready(Vfs::Vfs_handle const &) const override
 		{
 			return true;
 		}
diff --git a/repos/gems/src/lib/vfs/cbe_crypto/vfs.cc b/repos/gems/src/lib/vfs/cbe_crypto/vfs.cc
index cc309ebca0..832f266233 100644
--- a/repos/gems/src/lib/vfs/cbe_crypto/vfs.cc
+++ b/repos/gems/src/lib/vfs/cbe_crypto/vfs.cc
@@ -123,8 +123,7 @@ class Vfs_cbe_crypto::Encrypt_file_system : public Vfs::Single_file_system
 				return WRITE_OK;
 			}
 
-			bool read_ready() override { return true; }
-
+			bool read_ready()  const override { return true; }
 			bool write_ready() const override { return true; }
 		};
 
@@ -257,8 +256,7 @@ class Vfs_cbe_crypto::Decrypt_file_system : public Vfs::Single_file_system
 				return WRITE_OK;
 			}
 
-			bool read_ready() override { return true; }
-
+			bool read_ready()  const override { return true; }
 			bool write_ready() const override { return true; }
 		};
 
@@ -512,7 +510,7 @@ class Vfs_cbe_crypto::Keys_file_system : public Vfs::File_system
 				return SYNC_OK;
 			}
 
-			virtual bool read_ready() = 0;
+			virtual bool read_ready() const = 0;
 		};
 
 
@@ -606,7 +604,7 @@ class Vfs_cbe_crypto::Keys_file_system : public Vfs::File_system
 				return WRITE_ERR_INVALID;
 			}
 
-			bool read_ready() override { return true; }
+			bool read_ready() const override { return true; }
 
 		};
 
@@ -892,7 +890,7 @@ class Vfs_cbe_crypto::Keys_file_system : public Vfs::File_system
 			return READ_ERR_IO;
 		}
 
-		bool read_ready(Vfs::Vfs_handle *) override
+		bool read_ready(Vfs::Vfs_handle const &) const override
 		{
 			return true;
 		}
@@ -1006,8 +1004,7 @@ class Vfs_cbe_crypto::Management_file_system : public Vfs::Single_file_system
 				return WRITE_ERR_IO;
 			}
 
-			bool read_ready() override { return true; }
-
+			bool read_ready()  const override { return true; }
 			bool write_ready() const override { return true; }
 		};
 
diff --git a/repos/gems/src/lib/vfs/cbe_trust_anchor/vfs.cc b/repos/gems/src/lib/vfs/cbe_trust_anchor/vfs.cc
index ec92a4356c..fb7f163787 100644
--- a/repos/gems/src/lib/vfs/cbe_trust_anchor/vfs.cc
+++ b/repos/gems/src/lib/vfs/cbe_trust_anchor/vfs.cc
@@ -1369,8 +1369,7 @@ class Vfs_cbe_trust_anchor::Hashsum_file_system : public Vfs::Single_file_system
 				return WRITE_OK;
 			}
 
-			bool read_ready() override { return true; }
-
+			bool read_ready()  const override { return true; }
 			bool write_ready() const override { return true; }
 		};
 
@@ -1477,8 +1476,7 @@ class Vfs_cbe_trust_anchor::Generate_key_file_system : public Vfs::Single_file_s
 				return WRITE_ERR_IO;
 			}
 
-			bool read_ready() override { return true; }
-
+			bool read_ready()  const override { return true; }
 			bool write_ready() const override { return false; }
 		};
 
@@ -1607,8 +1605,7 @@ class Vfs_cbe_trust_anchor::Encrypt_file_system : public Vfs::Single_file_system
 				return WRITE_OK;
 			}
 
-			bool read_ready() override { return true; }
-
+			bool read_ready()  const override { return true; }
 			bool write_ready() const override { return true; }
 		};
 
@@ -1736,8 +1733,7 @@ class Vfs_cbe_trust_anchor::Decrypt_file_system : public Vfs::Single_file_system
 				return WRITE_OK;
 			}
 
-			bool read_ready() override { return true; }
-
+			bool read_ready()  const override { return true; }
 			bool write_ready() const override { return true; }
 		};
 
@@ -1858,8 +1854,7 @@ class Vfs_cbe_trust_anchor::Initialize_file_system : public Vfs::Single_file_sys
 				return WRITE_OK;
 			}
 
-			bool read_ready() override { return true; }
-
+			bool read_ready()  const override { return true; }
 			bool write_ready() const override { return true; }
 		};
 
diff --git a/repos/gems/src/lib/vfs/gpu/vfs.cc b/repos/gems/src/lib/vfs/gpu/vfs.cc
index 2d89c17c46..73a561bd1d 100644
--- a/repos/gems/src/lib/vfs/gpu/vfs.cc
+++ b/repos/gems/src/lib/vfs/gpu/vfs.cc
@@ -79,8 +79,7 @@ struct Vfs_gpu::File_system : Single_file_system
 			return WRITE_ERR_IO;
 		}
 
-		bool read_ready() override { return _complete; }
-
+		bool read_ready()  const override { return _complete; }
 		bool write_ready() const override { return true; }
 
 		Id_space::Id id() const { return _elem.id(); }
diff --git a/repos/gems/src/lib/vfs/import/plugin.cc b/repos/gems/src/lib/vfs/import/plugin.cc
index 0bb90e0c18..603d320471 100644
--- a/repos/gems/src/lib/vfs/import/plugin.cc
+++ b/repos/gems/src/lib/vfs/import/plugin.cc
@@ -284,7 +284,7 @@ class Vfs_import::File_system : public Vfs::File_system
 		                          file_size&) override {
 			return READ_ERR_INVALID; }
 
-		bool read_ready(Vfs_handle*) override {
+		bool read_ready(Vfs_handle const &) const override {
 			return true; }
 
 		bool write_ready(Vfs_handle const &) const override {
diff --git a/repos/gems/src/lib/vfs/pipe/plugin.cc b/repos/gems/src/lib/vfs/pipe/plugin.cc
index 2382e85795..86ce8c2cb0 100644
--- a/repos/gems/src/lib/vfs/pipe/plugin.cc
+++ b/repos/gems/src/lib/vfs/pipe/plugin.cc
@@ -76,7 +76,7 @@ struct Vfs_pipe::Pipe_handle : Vfs::Vfs_handle, private Pipe_handle_registry_ele
 	                 file_size count,
 	                 file_size &out_count);
 
-	bool read_ready();
+	bool read_ready()  const;
 	bool write_ready() const;
 	bool notify_read_ready();
 };
@@ -275,14 +275,16 @@ Vfs_pipe::Pipe_handle::write(const char *buf,
 
 
 Vfs_pipe::Read_result
-Vfs_pipe::Pipe_handle::read(char *buf,
-	                        file_size count,
-	                        file_size &out_count) {
-	return Pipe_handle::pipe.read(*this, buf, count, out_count); }
+Vfs_pipe::Pipe_handle::read(char *buf, file_size count, file_size &out_count)
+{
+	return Pipe_handle::pipe.read(*this, buf, count, out_count);
+}
 
 
-bool Vfs_pipe::Pipe_handle::read_ready() {
-	return !writer && !pipe.buffer.empty(); }
+bool Vfs_pipe::Pipe_handle::read_ready() const
+{
+	return !writer && !pipe.buffer.empty();
+}
 
 
 bool Vfs_pipe::Pipe_handle::write_ready() const
@@ -599,9 +601,9 @@ class Vfs_pipe::File_system : public Vfs::File_system
 			return READ_ERR_INVALID;
 		}
 
-		bool read_ready(Vfs_handle *vfs_handle) override
+		bool read_ready(Vfs_handle const &vfs_handle) const override
 		{
-			if (Pipe_handle *handle = dynamic_cast<Pipe_handle*>(vfs_handle))
+			if (Pipe_handle const *handle = dynamic_cast<Pipe_handle const *>(&vfs_handle))
 				return handle->read_ready();
 			return true;
 		}
diff --git a/repos/gems/src/lib/vfs/trace/vfs.cc b/repos/gems/src/lib/vfs/trace/vfs.cc
index b1c53f2ba4..2fa3f88bbb 100644
--- a/repos/gems/src/lib/vfs/trace/vfs.cc
+++ b/repos/gems/src/lib/vfs/trace/vfs.cc
@@ -147,8 +147,7 @@ class Vfs_trace::Trace_buffer_file_system : public Single_file_system
 				return WRITE_ERR_INVALID;
 			}
 
-			bool read_ready() override { return true; }
-
+			bool read_ready()  const override { return true; }
 			bool write_ready() const override { return false; }
 		};
 
diff --git a/repos/gems/src/lib/vfs/ttf/glyphs_file_system.h b/repos/gems/src/lib/vfs/ttf/glyphs_file_system.h
index 6dcd327e8a..4ae51b2b32 100644
--- a/repos/gems/src/lib/vfs/ttf/glyphs_file_system.h
+++ b/repos/gems/src/lib/vfs/ttf/glyphs_file_system.h
@@ -106,8 +106,7 @@ class Vfs::Glyphs_file_system : public Vfs::Single_file_system
 				return WRITE_ERR_IO;
 			}
 
-			bool read_ready() override { return true; }
-
+			bool read_ready()  const override { return true; }
 			bool write_ready() const override { return false; }
 		};
 
diff --git a/repos/libports/src/lib/libc/vfs_plugin.cc b/repos/libports/src/lib/libc/vfs_plugin.cc
index 95d0601ad4..56762754ec 100644
--- a/repos/libports/src/lib/libc/vfs_plugin.cc
+++ b/repos/libports/src/lib/libc/vfs_plugin.cc
@@ -219,7 +219,7 @@ namespace Libc {
 
 		handle->fs().notify_read_ready(handle);
 
-		return handle->fs().read_ready(handle);
+		return handle->fs().read_ready(*handle);
 	}
 
 	bool write_ready_from_kernel(File_descriptor *fd)
@@ -2721,7 +2721,7 @@ int Libc::Vfs_plugin::select(int nfds,
 			if (!handle) continue;
 
 			if (fd_in_readfds) {
-				if (handle->fs().read_ready(handle)) {
+				if (handle->fs().read_ready(*handle)) {
 					FD_SET(fd, readfds);
 					++nready;
 				} else {
diff --git a/repos/libports/src/lib/vfs/fatfs/vfs_fatfs.cc b/repos/libports/src/lib/vfs/fatfs/vfs_fatfs.cc
index 986cc19e60..a700a529f7 100644
--- a/repos/libports/src/lib/vfs/fatfs/vfs_fatfs.cc
+++ b/repos/libports/src/lib/vfs/fatfs/vfs_fatfs.cc
@@ -777,7 +777,7 @@ class Fatfs::File_system : public Vfs::File_system
 				FTRUNCATE_OK : FTRUNCATE_ERR_NO_PERM;
 		}
 
-		bool read_ready(Vfs_handle *) override { return true; }
+		bool read_ready(Vfs_handle const &) const override { return true; }
 
 		bool write_ready(Vfs_handle const &) const override
 		{
diff --git a/repos/libports/src/lib/vfs/jitterentropy/vfs_jitterentropy.h b/repos/libports/src/lib/vfs/jitterentropy/vfs_jitterentropy.h
index 54d5ffaa21..69159eef32 100644
--- a/repos/libports/src/lib/vfs/jitterentropy/vfs_jitterentropy.h
+++ b/repos/libports/src/lib/vfs/jitterentropy/vfs_jitterentropy.h
@@ -94,8 +94,7 @@ class Jitterentropy_file_system : public Vfs::Single_file_system
 					return WRITE_ERR_IO;
 				}
 
-				bool read_ready() override { return true; }
-
+				bool read_ready()  const override { return true; }
 				bool write_ready() const override { return false; }
 		};
 
diff --git a/repos/libports/src/lib/vfs/libusb/vfs_libusb.cc b/repos/libports/src/lib/vfs/libusb/vfs_libusb.cc
index a3c5cf4dc8..822390ef19 100644
--- a/repos/libports/src/lib/vfs/libusb/vfs_libusb.cc
+++ b/repos/libports/src/lib/vfs/libusb/vfs_libusb.cc
@@ -77,9 +77,10 @@ class Libusb_file_system : public Vfs::Single_file_system
 					libusb_genode_usb_connection(&_usb_connection);
 				}
 
-				bool read_ready() override
+				bool read_ready() const override
 				{
-					return _usb_connection.source()->ack_avail();
+					auto &nonconst_this = const_cast<Libusb_vfs_handle &>(*this);
+					return nonconst_this._usb_connection.source()->ack_avail();
 				}
 
 				Read_result read(char *dst, Vfs::file_size count,
diff --git a/repos/libports/src/lib/vfs/lwip/vfs.cc b/repos/libports/src/lib/vfs/lwip/vfs.cc
index 55f939c5ff..b8da2e6e27 100644
--- a/repos/libports/src/lib/vfs/lwip/vfs.cc
+++ b/repos/libports/src/lib/vfs/lwip/vfs.cc
@@ -426,8 +426,7 @@ struct Lwip::Socket_dir : Lwip::Directory
 		                           char const *src, file_size count,
 		                           file_size &out_count) = 0;
 
-		virtual bool read_ready(Lwip_file_handle&) = 0;
-
+		virtual bool read_ready (Lwip_file_handle const &) const = 0;
 		virtual bool write_ready(Lwip_file_handle const &) const = 0;
 
 		/**
@@ -891,7 +890,7 @@ class Lwip::Udp_socket_dir final :
 		 ** Socket_dir interface **
 		 **************************/
 
-		bool read_ready(Lwip_file_handle &handle) override
+		bool read_ready(Lwip_file_handle const &handle) const override
 		{
 			switch (handle.kind) {
 			case Lwip_file_handle::DATA:
@@ -1254,7 +1253,7 @@ class Lwip::Tcp_socket_dir final :
 		 ** Socket_dir interface **
 		 **************************/
 
-		bool read_ready(Lwip_file_handle &handle) override
+		bool read_ready(Lwip_file_handle const &handle) const override
 		{
 			switch (handle.kind) {
 			case Lwip_file_handle::DATA:
@@ -2111,12 +2110,13 @@ class Lwip::File_system final : public Vfs::File_system, public Lwip::Directory,
 			return false;
 		}
 
-		bool read_ready(Vfs_handle *vfs_handle) override
+		bool read_ready(Vfs_handle const &vfs_handle) const override
 		{
-			if (Lwip_file_handle *handle = dynamic_cast<Lwip_file_handle*>(vfs_handle)) {
-				if (handle->socket)
-					return handle->socket->read_ready(*handle);
-			}
+			Lwip_file_handle const * const handle_ptr =
+				dynamic_cast<Lwip_file_handle const *>(&vfs_handle);
+
+			if (handle_ptr && handle_ptr->socket)
+				return handle_ptr->socket->read_ready(*handle_ptr);
 
 			/*
 			 * in this case the polled file is a 'new_socket'
diff --git a/repos/libports/src/lib/vfs/oss/vfs_oss.cc b/repos/libports/src/lib/vfs/oss/vfs_oss.cc
index 00a5edae66..d4059ca371 100644
--- a/repos/libports/src/lib/vfs/oss/vfs_oss.cc
+++ b/repos/libports/src/lib/vfs/oss/vfs_oss.cc
@@ -285,7 +285,7 @@ struct Vfs::Oss_file_system::Audio
 			_in->overrun_sigh(sigh);
 		}
 
-		bool read_ready()
+		bool read_ready() const
 		{
 			return _info.ifrag_bytes > 0;
 		}
@@ -681,7 +681,7 @@ class Vfs::Oss_file_system::Data_file_system : public Single_file_system
 				return result;
 			}
 
-			bool read_ready() override
+			bool read_ready() const override
 			{
 				return _audio.read_ready();
 			}
diff --git a/repos/os/include/vfs/dir_file_system.h b/repos/os/include/vfs/dir_file_system.h
index b8bb62a28b..eb203e8686 100644
--- a/repos/os/include/vfs/dir_file_system.h
+++ b/repos/os/include/vfs/dir_file_system.h
@@ -965,12 +965,12 @@ class Vfs::Dir_file_system : public File_system
 			return FTRUNCATE_ERR_NO_PERM;
 		}
 
-		bool read_ready(Vfs_handle *handle) override
+		bool read_ready(Vfs_handle const &handle) const override
 		{
-			if (&handle->fs() == this)
+			if (&handle.fs() == this)
 				return true;
 
-			return handle->fs().read_ready(handle);
+			return handle.fs().read_ready(handle);
 		}
 
 		bool write_ready(Vfs_handle const &handle) const override
diff --git a/repos/os/include/vfs/file_io_service.h b/repos/os/include/vfs/file_io_service.h
index 491e00dd7e..eaf8d3e22d 100644
--- a/repos/os/include/vfs/file_io_service.h
+++ b/repos/os/include/vfs/file_io_service.h
@@ -67,7 +67,7 @@ struct Vfs::File_io_service : Interface
 	/**
 	 * Return true if the handle has readable data
 	 */
-	virtual bool read_ready(Vfs_handle *) = 0;
+	virtual bool read_ready(Vfs_handle const &) const = 0;
 
 	/**
 	 * Return true if the handle might accept a write operation
diff --git a/repos/os/include/vfs/readonly_value_file_system.h b/repos/os/include/vfs/readonly_value_file_system.h
index a1ea01c9a8..9aebe0df5f 100644
--- a/repos/os/include/vfs/readonly_value_file_system.h
+++ b/repos/os/include/vfs/readonly_value_file_system.h
@@ -72,8 +72,7 @@ class Vfs::Readonly_value_file_system : public Vfs::Single_file_system
 				return WRITE_ERR_IO;
 			}
 
-			bool read_ready() override { return true; }
-
+			bool read_ready()  const override { return true; }
 			bool write_ready() const override { return false; }
 		};
 
diff --git a/repos/os/include/vfs/single_file_system.h b/repos/os/include/vfs/single_file_system.h
index f84ead2d9a..868edc5e54 100644
--- a/repos/os/include/vfs/single_file_system.h
+++ b/repos/os/include/vfs/single_file_system.h
@@ -48,7 +48,7 @@ class Vfs::Single_file_system : public File_system
 				return SYNC_OK;
 			}
 
-			virtual bool read_ready() = 0;
+			virtual bool read_ready() const = 0;
 
 			virtual bool write_ready() const = 0;
 
@@ -132,8 +132,7 @@ class Vfs::Single_file_system : public File_system
 					return WRITE_ERR_INVALID;
 				}
 
-				bool read_ready() override { return true; }
-
+				bool read_ready()  const override { return true; }
 				bool write_ready() const override { return true; }
 		};
 
@@ -281,15 +280,12 @@ class Vfs::Single_file_system : public File_system
 			return WRITE_ERR_INVALID;
 		}
 
-		bool read_ready(Vfs_handle *vfs_handle) override
+		bool read_ready(Vfs_handle const &vfs_handle) const override
 		{
-			Single_vfs_handle *handle =
-				static_cast<Single_vfs_handle*>(vfs_handle);
+			Single_vfs_handle const &handle =
+				static_cast<Single_vfs_handle const &>(vfs_handle);
 
-			if (handle)
-				return handle->read_ready();
-
-			return false;
+			return handle.read_ready();
 		}
 
 		bool write_ready(Vfs_handle const &vfs_handle) const override
diff --git a/repos/os/include/vfs/value_file_system.h b/repos/os/include/vfs/value_file_system.h
index 24875ea792..9805147c8f 100644
--- a/repos/os/include/vfs/value_file_system.h
+++ b/repos/os/include/vfs/value_file_system.h
@@ -84,8 +84,7 @@ class Vfs::Value_file_system : public Vfs::Single_file_system
 				return WRITE_OK;
 			}
 
-			bool read_ready() override { return true; }
-
+			bool read_ready()  const override { return true; }
 			bool write_ready() const override { return true; }
 
 			private:
diff --git a/repos/os/src/lib/vfs/block_file_system.h b/repos/os/src/lib/vfs/block_file_system.h
index 28ba455ed2..ef4f1df033 100644
--- a/repos/os/src/lib/vfs/block_file_system.h
+++ b/repos/os/src/lib/vfs/block_file_system.h
@@ -337,8 +337,7 @@ class Vfs::Block_file_system::Data_file_system : public Single_file_system
 					return SYNC_OK;
 				}
 
-				bool read_ready() override { return true; }
-
+				bool read_ready()  const override { return true; }
 				bool write_ready() const override { return true; }
 		};
 
diff --git a/repos/os/src/lib/vfs/capture/plugin.cc b/repos/os/src/lib/vfs/capture/plugin.cc
index 1faa92e4bb..ac802c4e86 100644
--- a/repos/os/src/lib/vfs/capture/plugin.cc
+++ b/repos/os/src/lib/vfs/capture/plugin.cc
@@ -67,8 +67,7 @@ class Vfs_capture::Data_file_system : public Single_file_system
 				_capture(capture), _capture_ds(capture_ds)
 			{ }
 
-			bool read_ready() override { return true; }
-
+			bool read_ready()  const override { return true; }
 			bool write_ready() const override { return true; }
 
 			Read_result read(char *dst, file_size count,
diff --git a/repos/os/src/lib/vfs/fs_file_system.h b/repos/os/src/lib/vfs/fs_file_system.h
index d1cbbd8124..b5715da148 100644
--- a/repos/os/src/lib/vfs/fs_file_system.h
+++ b/repos/os/src/lib/vfs/fs_file_system.h
@@ -953,11 +953,11 @@ class Vfs::Fs_file_system : public File_system, private Remote_io
 			return result;
 		}
 
-		bool read_ready(Vfs_handle *vfs_handle) override
+		bool read_ready(Vfs_handle const &vfs_handle) const override
 		{
-			Fs_vfs_handle *handle = static_cast<Fs_vfs_handle *>(vfs_handle);
+			Fs_vfs_handle const &handle = static_cast<Fs_vfs_handle const &>(vfs_handle);
 
-			return handle->read_ready_state == Handle_state::Read_ready_state::READY;
+			return handle.read_ready_state == Handle_state::Read_ready_state::READY;
 		}
 
 		bool write_ready(Vfs_handle const &) const override
diff --git a/repos/os/src/lib/vfs/inline_file_system.h b/repos/os/src/lib/vfs/inline_file_system.h
index d60edd1e35..37a6f96ff8 100644
--- a/repos/os/src/lib/vfs/inline_file_system.h
+++ b/repos/os/src/lib/vfs/inline_file_system.h
@@ -89,8 +89,7 @@ class Vfs::Inline_file_system : public Single_file_system
 					return WRITE_ERR_INVALID;
 				}
 
-				bool read_ready() override { return true; }
-
+				bool read_ready()  const override { return true; }
 				bool write_ready() const override { return false; }
 		};
 
diff --git a/repos/os/src/lib/vfs/log_file_system.h b/repos/os/src/lib/vfs/log_file_system.h
index ffa0aec7f6..5d494bb497 100644
--- a/repos/os/src/lib/vfs/log_file_system.h
+++ b/repos/os/src/lib/vfs/log_file_system.h
@@ -126,8 +126,7 @@ class Vfs::Log_file_system : public Single_file_system
 					return WRITE_OK;
 				}
 
-				bool read_ready() override { return false; }
-
+				bool read_ready()  const override { return false; }
 				bool write_ready() const override { return true; }
 
 				Sync_result sync() override
diff --git a/repos/os/src/lib/vfs/null_file_system.h b/repos/os/src/lib/vfs/null_file_system.h
index 89733a6722..655b68148e 100644
--- a/repos/os/src/lib/vfs/null_file_system.h
+++ b/repos/os/src/lib/vfs/null_file_system.h
@@ -53,8 +53,7 @@ struct Vfs::Null_file_system : Single_file_system
 			return WRITE_OK;
 		}
 
-		bool read_ready() override { return false; }
-
+		bool read_ready()  const override { return false; }
 		bool write_ready() const override { return true; }
 	};
 
diff --git a/repos/os/src/lib/vfs/ram_file_system.h b/repos/os/src/lib/vfs/ram_file_system.h
index b345977b2a..9354331fd1 100644
--- a/repos/os/src/lib/vfs/ram_file_system.h
+++ b/repos/os/src/lib/vfs/ram_file_system.h
@@ -966,8 +966,7 @@ class Vfs::Ram_file_system : public Vfs::File_system
 			return handle->node.complete_read(dst, count, handle->seek(), out_count);
 		}
 
-		bool read_ready(Vfs_handle *) override { return true; }
-
+		bool read_ready (Vfs_handle const &) const override { return true; }
 		bool write_ready(Vfs_handle const &) const override { return true; }
 
 		Ftruncate_result ftruncate(Vfs_handle * const vfs_handle, file_size len) override
diff --git a/repos/os/src/lib/vfs/rom_file_system.h b/repos/os/src/lib/vfs/rom_file_system.h
index 9c5f28f937..b3e720c351 100644
--- a/repos/os/src/lib/vfs/rom_file_system.h
+++ b/repos/os/src/lib/vfs/rom_file_system.h
@@ -112,8 +112,7 @@ class Vfs::Rom_file_system : public Single_file_system
 					return WRITE_ERR_INVALID;
 				}
 
-				bool read_ready() override { return true; }
-
+				bool read_ready()  const override { return true; }
 				bool write_ready() const override { return false; }
 		};
 
diff --git a/repos/os/src/lib/vfs/rtc_file_system.h b/repos/os/src/lib/vfs/rtc_file_system.h
index 8de6ff66c2..f1aad5e915 100644
--- a/repos/os/src/lib/vfs/rtc_file_system.h
+++ b/repos/os/src/lib/vfs/rtc_file_system.h
@@ -81,8 +81,7 @@ class Vfs::Rtc_file_system : public Single_file_system
 					return WRITE_ERR_IO;
 				}
 
-				bool read_ready() override { return true; }
-
+				bool read_ready()  const override { return true; }
 				bool write_ready() const override { return false; }
 		};
 
diff --git a/repos/os/src/lib/vfs/symlink_file_system.h b/repos/os/src/lib/vfs/symlink_file_system.h
index c42341344e..d6c0b8244e 100644
--- a/repos/os/src/lib/vfs/symlink_file_system.h
+++ b/repos/os/src/lib/vfs/symlink_file_system.h
@@ -53,8 +53,7 @@ class Vfs::Symlink_file_system : public Single_file_system
 			                   file_size&) override {
 				return WRITE_ERR_INVALID; }
 
-			bool read_ready() override { return true; }
-
+			bool read_ready()  const override { return true; }
 			bool write_ready() const override { return false; }
 		};
 
diff --git a/repos/os/src/lib/vfs/tap/nic_file_system.h b/repos/os/src/lib/vfs/tap/nic_file_system.h
index aeea5f262e..3da29955ca 100644
--- a/repos/os/src/lib/vfs/tap/nic_file_system.h
+++ b/repos/os/src/lib/vfs/tap/nic_file_system.h
@@ -131,8 +131,13 @@ class Vfs::Nic_file_system::Nic_vfs_handle : public Single_vfs_handle
 		 * Vfs_handle interface *
 		 ************************/
 
-		bool read_ready() override {
-			return _link_state && _nic.rx()->packet_avail() && _nic.rx()->ready_to_ack(); }
+		bool read_ready() const override
+		{
+			auto &nonconst_this = const_cast<Nic_vfs_handle &>(*this);
+			auto &rx = *nonconst_this._nic.rx();
+
+			return _link_state && rx.packet_avail() && rx.ready_to_ack();
+		}
 
 		bool write_ready() const override
 		{
diff --git a/repos/os/src/lib/vfs/tap/uplink_file_system.h b/repos/os/src/lib/vfs/tap/uplink_file_system.h
index 967a3ee01f..e921b8ff8a 100644
--- a/repos/os/src/lib/vfs/tap/uplink_file_system.h
+++ b/repos/os/src/lib/vfs/tap/uplink_file_system.h
@@ -121,8 +121,13 @@ class Vfs::Uplink_file_system::Uplink_vfs_handle : public Single_vfs_handle,
 		 * Vfs_handle interface *
 		 ************************/
 
-		bool read_ready() override {
-			return _drv_link_state && _conn->rx()->packet_avail() && _conn->rx()->ready_to_ack(); }
+		bool read_ready() const override
+		{
+			auto &nonconst_this = const_cast<Uplink_vfs_handle &>(*this);
+			auto &rx = *nonconst_this._conn->rx();
+
+			return _drv_link_state && rx.packet_avail() && rx.ready_to_ack();
+		}
 
 		bool write_ready() const override
 		{
diff --git a/repos/os/src/lib/vfs/tar_file_system.h b/repos/os/src/lib/vfs/tar_file_system.h
index ea6c64dcd3..054e2c8d55 100644
--- a/repos/os/src/lib/vfs/tar_file_system.h
+++ b/repos/os/src/lib/vfs/tar_file_system.h
@@ -775,8 +775,7 @@ class Vfs::Tar_file_system : public File_system
 			return FTRUNCATE_ERR_NO_PERM;
 		}
 
-		bool read_ready(Vfs_handle *) override { return true; }
-
+		bool read_ready (Vfs_handle const &) const override { return true; }
 		bool write_ready(Vfs_handle const &) const override { return false; }
 };
 
diff --git a/repos/os/src/lib/vfs/terminal_file_system.h b/repos/os/src/lib/vfs/terminal_file_system.h
index 207c8e3893..bd08b2b72f 100644
--- a/repos/os/src/lib/vfs/terminal_file_system.h
+++ b/repos/os/src/lib/vfs/terminal_file_system.h
@@ -134,7 +134,7 @@ class Vfs::Terminal_file_system::Data_file_system : public Single_file_system
 				_raw(raw)
 			{ }
 
-			bool read_ready() override {
+			bool read_ready() const override {
 				return !_read_buffer.empty(); }
 
 			bool write_ready() const override { return true; }
diff --git a/repos/os/src/lib/vfs/zero_file_system.h b/repos/os/src/lib/vfs/zero_file_system.h
index da85585320..78bc9de746 100644
--- a/repos/os/src/lib/vfs/zero_file_system.h
+++ b/repos/os/src/lib/vfs/zero_file_system.h
@@ -81,8 +81,7 @@ struct Vfs::Zero_file_system : Single_file_system
 			return WRITE_OK;
 		}
 
-		bool read_ready() override { return true; }
-
+		bool read_ready()  const override { return true; }
 		bool write_ready() const override { return true; }
 	};
 
diff --git a/repos/os/src/server/vfs/node.h b/repos/os/src/server/vfs/node.h
index 62fb2be59f..5ccd38c5f9 100644
--- a/repos/os/src/server/vfs/node.h
+++ b/repos/os/src/server/vfs/node.h
@@ -351,7 +351,7 @@ class Vfs_server::Io_node : public Vfs_server::Node,
 		{
 			_read_ready_state = Read_ready_state::REQUESTED;
 
-			if (_handle.fs().read_ready(&_handle)) {
+			if (_handle.fs().read_ready(_handle)) {
 				/* if the handle is ready, send a packet back immediately */
 				read_ready_response();
 			} else {