[HTTP Cache] Prevent memory backend from exceeding its max size

net/disk_cache/memory/mem_backend_impl.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/disk_cache/memory/mem_backend_impl.h"
 
 #include <algorithm>
 #include <functional>
 #include <utility>
 
@@ skipping 30 matching lines @@
 }  // namespace
 
 MemBackendImpl::MemBackendImpl(net::NetLog* net_log)
     : max_size_(0), current_size_(0), net_log_(net_log), weak_factory_(this) {
 }
 
 MemBackendImpl::~MemBackendImpl() {
   DCHECK(CheckLRUListOrder(lru_list_));
   while (!entries_.empty())
     entries_.begin()->second->Doom();
-  DCHECK(!current_size_);
+  DCHECK_EQ(0, current_size_);

[jkarlin, 2017/03/30 15:04:42]

Hmm. I'm skeptical that this DCHECK even makes sense. Doomed entries can  live
beyond the backend and current_size_ isn't decremented until the doomed entry is
deleted.

[Randy Smith (Not in Mondays), 2017/03/30 16:38:11]

Plausible skepticism.  I'd say not your problem, though.

[jkarlin, 2017/03/30 17:18:27]

Acknowledged.

 }
 
 // static
 std::unique_ptr<Backend> MemBackendImpl::CreateBackend(int max_bytes,
                                                        net::NetLog* net_log) {
   std::unique_ptr<MemBackendImpl> cache(new MemBackendImpl(net_log));
   cache->SetMaxSize(max_bytes);
   if (cache->Init())
     return std::move(cache);
 
@@ skipping 59 matching lines @@
   // LinkedList<>::RemoveFromList() removes |entry| from |lru_list_|.
   entry->RemoveFromList();
 }
 
 void MemBackendImpl::ModifyStorageSize(int32_t delta) {
   current_size_ += delta;
   if (delta > 0)
     EvictIfNeeded();
 }
 
+bool MemBackendImpl::HasExceededStorageSize() const {
+  return current_size_ > max_size_;
+}
+
 net::CacheType MemBackendImpl::GetCacheType() const {
   return net::MEMORY_CACHE;
 }
 
 int32_t MemBackendImpl::GetEntryCount() const {
   return static_cast<int32_t>(entries_.size());
 }
 
 int MemBackendImpl::OpenEntry(const std::string& key,
                               Entry** entry,
@@ skipping 174 matching lines @@
   base::LinkNode<MemEntryImpl>* entry = lru_list_.head();
   while (current_size_ > target_size && entry != lru_list_.end()) {
     MemEntryImpl* to_doom = entry->value();
     entry = entry->next();
     if (!to_doom->InUse())
       to_doom->Doom();
   }
 }
 
 }  // namespace disk_cache