core: restructure IO queue callbacks

mc_resp is the proper owner of a pending IO once it's been initialized;
release it during resp_finish(). Also adds a completion callback which
runs on the submitted stack after returning to the worker thread but
before the response is transmitted.

allows re-queueing for pending IO if processing a response generates
another pending IO. also allows a further refactor to run more extstore
code on the worker thread instead of the IO threads.

uses proper conn_io_queue state to describe connections waiting for
pending IO's.

1 files changed, 10 insertions, 2 deletions

diff --git a/storage.h b/storage.h
index 05e420d..ca59102 100644
--- a/storage.h
+++ b/storage.h
@@ -11,18 +11,26 @@ void storage_delete(void *e, item *it);
 #define STORAGE_delete(...)
 #endif
 
+// API.
 void storage_stats(ADD_STAT add_stats, conn *c);
 void process_extstore_stats(ADD_STAT add_stats, conn *c);
 bool storage_validate_item(void *e, item *it);
 int storage_get_item(conn *c, item *it, mc_resp *resp);
-void storage_submit_cb(void *ctx, io_pending_t *pending);
-void storage_free_cb(void *ctx, io_pending_t *pending);
+
+// callbacks for the IO queue subsystem.
+void storage_submit_cb(void *ctx, void *stack);
+void storage_complete_cb(void *ctx, void *stack);
+void storage_finalize_cb(io_pending_t *pending);
+
+// Thread functions.
 int start_storage_write_thread(void *arg);
 void storage_write_pause(void);
 void storage_write_resume(void);
 int start_storage_compact_thread(void *arg);
 void storage_compact_pause(void);
 void storage_compact_resume(void);
+
+// Init functions.
 struct extstore_conf_file *storage_conf_parse(char *arg, unsigned int page_size);
 void *storage_init_config(struct settings *s);
 int storage_read_config(void *conf, char **subopt);