quota-count: Cache quota usage within the same ioloop run.

This mainly means that when both STORAGE and MESSAGES quota is looked up we
don't need to calculate them twice.

src/plugins/quota/quota-count.c

@@ -1,9 +1,17 @@
 /* Copyright (c) 2006-2016 Dovecot authors, see the included COPYING file */
 
 #include "lib.h"
+#include "ioloop.h"
 #include "mailbox-list-iter.h"
 #include "quota-private.h"
 
+struct count_quota_root {
+	struct quota_root root;
+
+	struct timeval cache_timeval;
+	uint64_t cached_bytes, cached_count;
+};
+
 struct quota_mailbox_iter {
 	struct quota_root *root;
 	struct mail_namespace *ns;
@@ -137,10 +145,19 @@ quota_mailbox_iter_next(struct quota_mailbox_iter *iter)
 
 int quota_count(struct quota_root *root, uint64_t *bytes_r, uint64_t *count_r)
 {
+	struct count_quota_root *croot = (struct count_quota_root *)root;
 	struct quota_mailbox_iter *iter;
 	const struct mailbox_info *info;
 	int ret = 0, ret2;
 
+	if (croot->cache_timeval.tv_usec == ioloop_timeval.tv_usec &&
+	    croot->cache_timeval.tv_sec == ioloop_timeval.tv_sec &&
+	    ioloop_timeval.tv_sec != 0) {
+		*bytes_r = croot->cached_bytes;
+		*count_r = croot->cached_count;
+		return 1;
+	}
+
 	*bytes_r = *count_r = 0;
 	if (root->recounting)
 		return 0;
@@ -159,12 +176,20 @@ int quota_count(struct quota_root *root, uint64_t *bytes_r, uint64_t *count_r)
 	}
 	quota_mailbox_iter_deinit(&iter);
 	root->recounting = FALSE;
+	if (ret > 0) {
+		croot->cache_timeval = ioloop_timeval;
+		croot->cached_bytes = *bytes_r;
+		croot->cached_count = *count_r;
+	}
 	return ret < 0 ? -1 : 0;
 }
 
 static struct quota_root *count_quota_alloc(void)
 {
-	return i_new(struct quota_root, 1);
+	struct count_quota_root *root;
+
+	root = i_new(struct count_quota_root, 1);
+	return &root->root;
 }
 
 static int count_quota_init(struct quota_root *root, const char *args,
@@ -273,6 +298,9 @@ static int
 count_quota_update(struct quota_root *root,
 		   struct quota_transaction_context *ctx)
 {
+	struct count_quota_root *croot = (struct count_quota_root *)root;
+
+	croot->cache_timeval.tv_sec = 0;
 	if (ctx->recalculate) {
 		if (quota_count_recalculate(root) < 0)
 			return -1;