io_queue: rename io_desc_read_write to queued_io_request_completion

This patch is a part of the preparation to route discard requests
via I/O scheduler.

The mentioned 'io_desc_read_write' is used to track the completion
of read and write requests submitted to 'io_sink'. It implements
'io_completion' interface -- its functions are invoked when the
processing of a request via 'reactor_backend' is finished.

In spite of the fact that 'fallocate()' is not supported by Linux AIO
and therefore, discards will not be submitted to 'io_sink' and processed
by 'reactor_backend', discard requests will need to notify 'io_queue'
about completion in the same way that reads and writes do. Thus, to avoid
code duplication 'io_desc_read_write' is renamed to 'queued_io_request_completion'
as it will be used by discard requests.

Signed-off-by: Patryk Wrobel <[email protected]>

include/seastar/core/io_queue.hh

@@ -65,7 +65,7 @@ class io_sink;
 using shard_id = unsigned;
 using stream_id = unsigned;
 
-class io_desc_read_write;
+class queued_io_request_completion;
 class queued_io_request;
 class io_group;
 
@@ -163,10 +163,10 @@ public:
     future<size_t> submit_io_write(internal::priority_class priority_class,
             size_t len, internal::io_request req, io_intent* intent, iovec_keeper iovs = {}) noexcept;
 
-    void submit_request(io_desc_read_write* desc, internal::io_request req) noexcept;
+    void submit_request(queued_io_request_completion* desc, internal::io_request req) noexcept;
     void cancel_request(queued_io_request& req) noexcept;
     void complete_cancelled_request(queued_io_request& req) noexcept;
-    void complete_request(io_desc_read_write& desc) noexcept;
+    void complete_request(queued_io_request_completion& desc) noexcept;
 
     [[deprecated("I/O queue users should not track individual requests, but resources (weight, size) passing through the queue")]]
     size_t queued_requests() const {

src/core/io_queue.cc

@@ -211,7 +211,7 @@ class io_queue::priority_class_data {
     metrics::metric_groups metric_groups;
 };
 
-class io_desc_read_write final : public io_completion {
+class queued_io_request_completion final : public io_completion {
     io_queue& _ioq;
     io_queue::priority_class_data& _pclass;
     io_queue::clock_type::time_point _ts;
@@ -222,7 +222,7 @@ class io_desc_read_write final : public io_completion {
     iovec_keeper _iovs;
 
 public:
-    io_desc_read_write(io_queue& ioq, io_queue::priority_class_data& pc, stream_id stream, io_direction_and_length dnl, fair_queue_entry::capacity_t cap, iovec_keeper iovs)
+    queued_io_request_completion(io_queue& ioq, io_queue::priority_class_data& pc, stream_id stream, io_direction_and_length dnl, fair_queue_entry::capacity_t cap, iovec_keeper iovs)
         : _ioq(ioq)
         , _pclass(pc)
         , _ts(io_queue::clock_type::now())
@@ -277,7 +277,7 @@ class queued_io_request : private internal::io_request {
     const stream_id _stream;
     fair_queue_entry _fq_entry;
     internal::cancellable_queue::link _intent;
-    std::unique_ptr<io_desc_read_write> _desc;
+    std::unique_ptr<queued_io_request_completion> _desc;
 
     bool is_cancelled() const noexcept { return !_desc; }
 
@@ -287,7 +287,7 @@ class queued_io_request : private internal::io_request {
         , _ioq(q)
         , _stream(_ioq.request_stream(dnl))
         , _fq_entry(cap)
-        , _desc(std::make_unique<io_desc_read_write>(_ioq, pc, _stream, dnl, cap, std::move(iovs)))
+        , _desc(std::make_unique<queued_io_request_completion>(_ioq, pc, _stream, dnl, cap, std::move(iovs)))
     {
     }
 
@@ -548,7 +548,7 @@ void io_queue::update_flow_ratio() noexcept {
 }
 
 void
-io_queue::complete_request(io_desc_read_write& desc) noexcept {
+io_queue::complete_request(queued_io_request_completion& desc) noexcept {
     _requests_executing--;
     _requests_completed++;
     _streams[desc.stream()].notify_request_finished(desc.capacity());
@@ -1038,7 +1038,7 @@ void io_queue::poll_io_queue() {
     }
 }
 
-void io_queue::submit_request(io_desc_read_write* desc, internal::io_request req) noexcept {
+void io_queue::submit_request(queued_io_request_completion* desc, internal::io_request req) noexcept {
     _queued_requests--;
     _requests_executing++;
     _requests_dispatched++;