Fix issues discovered by Coverity (#2535)

src/curl.cpp

@@ -1858,7 +1858,9 @@ bool S3fsCurl::AddUserAgent(const CurlUniquePtr& hCurl)
         return false;
     }
     if(S3fsCurl::IsUserAgentFlag()){
-        curl_easy_setopt(hCurl, CURLOPT_USERAGENT, S3fsCurl::userAgent.c_str());
+        if(CURLE_OK != curl_easy_setopt(hCurl, CURLOPT_USERAGENT, S3fsCurl::userAgent.c_str())){
+            return false;
+        }
     }
     return true;
 }

src/curl_multi.cpp

@@ -115,7 +115,7 @@ bool S3fsMultiCurl::SetS3fsCurlObject(std::unique_ptr<S3fsCurl> s3fscurl)
 int S3fsMultiCurl::MultiPerform()
 {
     std::map<std::thread::id, std::pair<std::thread, std::future<int>>> threads;
-    bool                     success = true;
+    int                      result = 0;
     bool                     isMultiHead = false;
     Semaphore                sem(GetMaxParallelism());
 
@@ -164,12 +164,13 @@ int S3fsMultiCurl::MultiPerform()
         long int int_retval = it->second.second.get();
         if (int_retval && !(int_retval == -ENOENT && isMultiHead)) {
             S3FS_PRN_WARN("thread terminated with non-zero return code: %ld", int_retval);
+            result = int_retval;
         }
         threads.erase(it);
     }
     completed_tids.clear();
 
-    return success ? 0 : -EIO;
+    return result;
 }
 
 int S3fsMultiCurl::MultiRead()

src/fdcache_entity.cpp

@@ -1203,13 +1203,13 @@ int FdEntity::NoCacheLoadAndPost(PseudoFdInfo* pseudo_obj, off_t start, off_t si
                 fdpage page(iter->offset, start - iter->offset, iter->loaded, false);
                 iter->bytes -= (start - iter->offset);
                 iter->offset = start;
-                pagelist.pages.insert(iter, page);
+                iter = pagelist.pages.insert(iter, page);
             }
             if(0 != size && start + size < iter->next()){
                 fdpage page(iter->offset, start + size - iter->offset, true, false);
                 iter->bytes -= (start + size - iter->offset);
                 iter->offset = start + size;
-                pagelist.pages.insert(iter, page);
+                iter = pagelist.pages.insert(iter, page);
             }else{
                 iter->loaded   = true;
                 iter->modified = false;

test/write_multiblock.cc

@@ -73,6 +73,9 @@ static std::unique_ptr<unsigned char[]> create_random_data(off_t size)
             readcnt = 0;
         }
     }
+
+    close(fd);
+
     return pbuff;
 }