Back out r269483 and the line of fixes that followed it.

base/memory/discardable_memory_mac.cc

 // Copyright (c) 2013 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 "base/memory/discardable_memory.h"
 
 #include <mach/mach.h>
+#include <sys/mman.h>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/logging.h"
-#include "base/mac/mach_logging.h"
-#include "base/mac/scoped_mach_vm.h"
 #include "base/memory/discardable_memory_emulated.h"
 #include "base/memory/discardable_memory_malloc.h"
 #include "base/memory/scoped_ptr.h"
 
 namespace base {
 namespace {
 
 // The VM subsystem allows tagging of memory and 240-255 is reserved for
 // application use (see mach/vm_statistics.h). Pick 252 (after chromium's atomic
 // weight of ~52).
 const int kDiscardableMemoryTag = VM_MAKE_TAG(252);
 
 class DiscardableMemoryMac : public DiscardableMemory {
  public:
   explicit DiscardableMemoryMac(size_t size)
-      : memory_(0, 0),
-        size_(mach_vm_round_page(size)) {
+      : buffer_(0),
+        size_(size) {
   }
 
   bool Initialize() {
-    DCHECK_EQ(memory_.size(), 0u);
-    vm_address_t address = 0;
     kern_return_t ret = vm_allocate(mach_task_self(),
-                                    &address,
+                                    &buffer_,
                                     size_,
                                     VM_FLAGS_PURGABLE |
-                                        VM_FLAGS_ANYWHERE |
-                                        kDiscardableMemoryTag);
+                                    VM_FLAGS_ANYWHERE |
+                                    kDiscardableMemoryTag);
     if (ret != KERN_SUCCESS) {
-      MACH_DLOG(ERROR, ret) << "vm_allocate";
+      DLOG(ERROR) << "vm_allocate() failed";
       return false;
     }
 
-    memory_.reset(address, size_);
-
     return true;
   }
 
   virtual ~DiscardableMemoryMac() {
+    if (buffer_)
+      vm_deallocate(mach_task_self(), buffer_, size_);
   }
 
   virtual DiscardableMemoryLockStatus Lock() OVERRIDE {
-    kern_return_t ret;
-    MACH_DCHECK((ret = vm_protect(mach_task_self(),
-                                  memory_.address(),
-                                  memory_.size(),
-                                  FALSE,
-                                  VM_PROT_DEFAULT)) == KERN_SUCCESS, ret);
+    DCHECK_EQ(0, mprotect(reinterpret_cast<void*>(buffer_),
+                          size_,
+                          PROT_READ | PROT_WRITE));
     int state = VM_PURGABLE_NONVOLATILE;
-    ret = vm_purgable_control(mach_task_self(),
-                              memory_.address(),
-                              VM_PURGABLE_SET_STATE,
-                              &state);
+    kern_return_t ret = vm_purgable_control(mach_task_self(),
+                                            buffer_,
+                                            VM_PURGABLE_SET_STATE,
+                                            &state);
     if (ret != KERN_SUCCESS)
       return DISCARDABLE_MEMORY_LOCK_STATUS_FAILED;
 
     return state & VM_PURGABLE_EMPTY ? DISCARDABLE_MEMORY_LOCK_STATUS_PURGED
                                      : DISCARDABLE_MEMORY_LOCK_STATUS_SUCCESS;
   }
 
   virtual void Unlock() OVERRIDE {
     int state = VM_PURGABLE_VOLATILE | VM_VOLATILE_GROUP_DEFAULT;
     kern_return_t ret = vm_purgable_control(mach_task_self(),
-                                            memory_.address(),
+                                            buffer_,
                                             VM_PURGABLE_SET_STATE,
                                             &state);
-    MACH_DLOG_IF(ERROR, ret != KERN_SUCCESS, ret) << "vm_purgable_control";
-    MACH_DCHECK((ret = vm_protect(mach_task_self(),
-                                  memory_.address(),
-                                  memory_.size(),
-                                  FALSE,
-                                  VM_PROT_NONE)) == KERN_SUCCESS, ret);
+    DCHECK_EQ(0, mprotect(reinterpret_cast<void*>(buffer_), size_, PROT_NONE));
+    if (ret != KERN_SUCCESS)
+      DLOG(ERROR) << "Failed to unlock memory.";
   }
 
   virtual void* Memory() const OVERRIDE {
-    return reinterpret_cast<void*>(memory_.address());
+    return reinterpret_cast<void*>(buffer_);
   }
 
  private:
-  mac::ScopedMachVM memory_;
-  size_t size_;
+  vm_address_t buffer_;
+  const size_t size_;
 
   DISALLOW_COPY_AND_ASSIGN(DiscardableMemoryMac);
 };
 
 }  // namespace
 
 // static
 void DiscardableMemory::RegisterMemoryPressureListeners() {
   internal::DiscardableMemoryEmulated::RegisterMemoryPressureListeners();
 }
@@ skipping 51 matching lines @@
 }
 
 // static
 void DiscardableMemory::PurgeForTesting() {
   int state = 0;
   vm_purgable_control(mach_task_self(), 0, VM_PURGABLE_PURGE_ALL, &state);
   internal::DiscardableMemoryEmulated::PurgeForTesting();
 }
 
 }  // namespace base