fix

src/server/models/attachment.js

@@ -35,7 +35,7 @@ module.exports = function(crowi) {
     //   2. ensure backward compatibility of data
 
     // return `/files/${this._id}`;
-    return fileUploader.generateUrl(this.filePath);
+     return fileUploader.generateUrl(this.filePath);
   });
 
   attachmentSchema.statics.findById = function(id) {

src/server/routes/attachment.js

@@ -140,8 +140,9 @@ module.exports = function(crowi, app) {
 
     var tmpFile = req.file || null;
     const usingFilesSize = await fileUploader.getCollectionSize();
-    if (tmpFile.size > usingFilesSize) {
-      throw new Error('mongoDB for file uploading reaches the limit');
+    const usableCapacity = +process.env.GRIDFS_LIMIT - usingFilesSize;
+    if (tmpFile.size > usableCapacity) {
+      throw new Error('mongoDB for file uploading reaches limit');
     }
     debug('Uploaded tmpFile: ', tmpFile);
     if (!tmpFile) {