quota: Add error_r to get_resource() of quota_backend_vfuncs

src/plugins/quota/quota-count.c

@@ -228,13 +228,16 @@ count_quota_root_get_resources(struct quota_root *root ATTR_UNUSED)
 
 static int
 count_quota_get_resource(struct quota_root *_root,
-			 const char *name, uint64_t *value_r)
+			 const char *name, uint64_t *value_r,
+			 const char **error_r)
 {
 	struct count_quota_root *root = (struct count_quota_root *)_root;
 	uint64_t bytes, count;
 
-	if (quota_count_cached(root, &bytes, &count) < 0)
+	if (quota_count_cached(root, &bytes, &count) < 0) {
+		*error_r = "quota-count failed";
 		return -1;
+	}
 
 	if (strcmp(name, QUOTA_NAME_STORAGE_BYTES) == 0)
 		*value_r = bytes;

src/plugins/quota/quota-dict.c

@@ -140,7 +140,8 @@ dict_quota_count(struct dict_quota_root *root,
 
 static int
 dict_quota_get_resource(struct quota_root *_root,
-			const char *name, uint64_t *value_r)
+			const char *name, uint64_t *value_r,
+			const char **error_r)
 {
 	struct dict_quota_root *root = (struct dict_quota_root *)_root;
 	bool want_bytes;
@@ -176,6 +177,8 @@ dict_quota_get_resource(struct quota_root *_root,
 					       value_r);
 		}
 	}
+	if (ret < 0)
+		*error_r = "quota-dict failed";
 	return ret;
 }
 

src/plugins/quota/quota-dirsize.c

@@ -192,7 +192,7 @@ get_quota_root_usage(struct quota_root *root, uint64_t *value_r)
 
 static int
 dirsize_quota_get_resource(struct quota_root *_root, const char *name,
-			   uint64_t *value_r)
+			   uint64_t *value_r, const char **error_r)
 {
 	int ret;
 
@@ -201,6 +201,9 @@ dirsize_quota_get_resource(struct quota_root *_root, const char *name,
 
 	ret = get_quota_root_usage(_root, value_r);
 
+	if (ret < 0)
+		*error_r = "quota-dirsize failed";
+
 	return ret < 0 ? -1 : 1;
 }
 

src/plugins/quota/quota-fs.c

@@ -856,7 +856,7 @@ static bool fs_quota_match_box(struct quota_root *_root, struct mailbox *box)
 
 static int
 fs_quota_get_resource(struct quota_root *_root, const char *name,
-		      uint64_t *value_r)
+		      uint64_t *value_r, const char **error_r)
 {
 	struct fs_quota_root *root = (struct fs_quota_root *)_root;
 	uint64_t bytes_value, count_value;
@@ -887,6 +887,8 @@ fs_quota_get_resource(struct quota_root *_root, const char *name,
 						     &count_value, &count_limit);
 		}
 	}
+	if (ret < 0)
+		*error_r = "quota-fs failed";
 	if (ret <= 0)
 		return ret;
 

src/plugins/quota/quota-imapc.c

@@ -423,12 +423,14 @@ imapc_quota_root_get_resources(struct quota_root *root ATTR_UNUSED)
 
 static int
 imapc_quota_get_resource(struct quota_root *_root, const char *name,
-			 uint64_t *value_r)
+			 uint64_t *value_r, const char **error_r)
 {
 	struct imapc_quota_root *root = (struct imapc_quota_root *)_root;
 
-	if (imapc_quota_refresh(root) < 0)
+	if (imapc_quota_refresh(root) < 0) {
+		*error_r = "quota-imapc failed";
 		return -1;
+	}
 
 	if (strcmp(name, QUOTA_NAME_STORAGE_BYTES) == 0)
 		*value_r = root->bytes_last;

src/plugins/quota/quota-maildir.c

@@ -836,13 +836,15 @@ maildir_quota_root_get_resources(struct quota_root *root ATTR_UNUSED)
 
 static int
 maildir_quota_get_resource(struct quota_root *_root, const char *name,
-			   uint64_t *value_r)
+			   uint64_t *value_r, const char **error_r)
 {
 	struct maildir_quota_root *root = (struct maildir_quota_root *)_root;
 	bool recalculated;
 
-	if (maildirquota_refresh(root, &recalculated) < 0)
+	if (maildirquota_refresh(root, &recalculated) < 0) {
+		*error_r = "quota-maildir failed";
 		return -1;
+	}
 
 	if (strcmp(name, QUOTA_NAME_STORAGE_BYTES) == 0) {
 		*value_r = root->total_bytes;

src/plugins/quota/quota-private.h

@@ -69,7 +69,8 @@ struct quota_backend_vfuncs {
 	/* Returns 1 if value was returned, 0 if resource name doesn't exist,
 	   -1 if internal error. */
 	int (*get_resource)(struct quota_root *root,
-			    const char *name, uint64_t *value_r);
+			    const char *name, uint64_t *value_r,
+			    const char **error_r);
 
 	int (*update)(struct quota_root *root, 
 		      struct quota_transaction_context *ctx);

src/plugins/quota/quota.c

@@ -772,11 +772,12 @@ quota_get_resource(struct quota_root *root, const char *mailbox_name,
 
 	/* Get the value first. This call may also update quota limits if
 	   they're defined externally. */
-	ret = root->backend.v.get_resource(root, name, value_r);
+	const char *error;
+	ret = root->backend.v.get_resource(root, name, value_r, &error);
 	if (ret < 0) {
 		*error_r = t_strdup_printf(
-			"Could not get %s from quota backend for mailbox %s",
-			name, mailbox_name);
+			"Could not get %s from quota backend for mailbox %s: %s",
+			name, mailbox_name, error);
 		return QUOTA_GET_RESULT_INTERNAL_ERROR;
 	} else if (ret == 0) {
 		*error_r = t_strdup_printf(
@@ -785,7 +786,6 @@ quota_get_resource(struct quota_root *root, const char *mailbox_name,
 		return QUOTA_GET_RESULT_UNKNOWN_RESOURCE;
 	}
 
-	const char *error;
 	if (quota_root_get_rule_limits(root, mailbox_name,
 				       &bytes_limit, &count_limit,
 				       &ignored, &error) < 0) {