content: Close in-process discardable memory segments.

This prevents in-process discardable shared memory instances
from requiring an open file descriptor.

BUG=489174
TEST=base_unittests --gtest_filter=DiscardableSharedMemory.Close

Review URL: https://codereview.chromium.org/1146103002

Cr-Commit-Position: refs/heads/master@{#330806}

base/memory/discardable_shared_memory.cc

@@ -157,6 +157,14 @@ bool DiscardableSharedMemory::Map(size_t size) {
   return true;
 }
 
+bool DiscardableSharedMemory::Unmap() {
+  if (!shared_memory_.Unmap())
+    return false;
+
+  mapped_size_ = 0;
+  return true;
+}
+
 DiscardableSharedMemory::LockResult DiscardableSharedMemory::Lock(
     size_t offset, size_t length) {
   DCHECK_EQ(AlignToPageSize(offset), offset);
@@ -212,11 +220,12 @@ DiscardableSharedMemory::LockResult DiscardableSharedMemory::Lock(
 
 #if defined(OS_ANDROID)
   SharedMemoryHandle handle = shared_memory_.handle();
-  DCHECK(SharedMemory::IsHandleValid(handle));
+  if (SharedMemory::IsHandleValid(handle)) {
     if (ashmem_pin_region(
             handle.fd, AlignToPageSize(sizeof(SharedState)) + offset, length)) {
       return PURGED;
     }
+  }
 #endif
 
   return SUCCESS;
@@ -237,11 +246,12 @@ void DiscardableSharedMemory::Unlock(size_t offset, size_t length) {
 
 #if defined(OS_ANDROID)
   SharedMemoryHandle handle = shared_memory_.handle();
-  DCHECK(SharedMemory::IsHandleValid(handle));
+  if (SharedMemory::IsHandleValid(handle)) {
     if (ashmem_unpin_region(
             handle.fd, AlignToPageSize(sizeof(SharedState)) + offset, length)) {
       DPLOG(ERROR) << "ashmem_unpin_region() failed";
     }
+  }
 #endif
 
   size_t start = offset / base::GetPageSize();
@@ -336,9 +346,7 @@ bool DiscardableSharedMemory::IsMemoryResident() const {
 }
 
 void DiscardableSharedMemory::Close() {
-  shared_memory_.Unmap();
   shared_memory_.Close();
-  mapped_size_ = 0;
 }
 
 #if defined(DISCARDABLE_SHARED_MEMORY_SHRINKING)

base/memory/discardable_shared_memory.h

@@ -48,6 +48,11 @@ class BASE_EXPORT DiscardableSharedMemory {
   // Returns true on success, false otherwise.
   bool Map(size_t size);
 
+  // Unmaps the discardable shared memory from the caller's address space.
+  // Returns true if successful; returns false on error or if the memory is
+  // not mapped.
+  bool Unmap();
+
   // The actual size of the mapped memory (may be larger than requested).
   size_t mapped_size() const { return mapped_size_; }
 

base/memory/discardable_shared_memory_unittest.cc

@@ -306,11 +306,34 @@ TEST(DiscardableSharedMemoryTest, MappedSize) {
 
   EXPECT_LE(kDataSize, memory.mapped_size());
 
-  // Mapped size should be 0 after memory segment has been closed.
-  memory.Close();
+  // Mapped size should be 0 after memory segment has been unmapped.
+  rv = memory.Unmap();
+  EXPECT_TRUE(rv);
   EXPECT_EQ(0u, memory.mapped_size());
 }
 
+TEST(DiscardableSharedMemoryTest, Close) {
+  const uint32 kDataSize = 1024;
+
+  TestDiscardableSharedMemory memory;
+  bool rv = memory.CreateAndMap(kDataSize);
+  ASSERT_TRUE(rv);
+
+  // Mapped size should be unchanged after memory segment has been closed.
+  memory.Close();
+  EXPECT_LE(kDataSize, memory.mapped_size());
+
+  // Memory is initially locked. Unlock it.
+  memory.SetNow(Time::FromDoubleT(1));
+  memory.Unlock(0, 0);
+
+  // Lock and unlock memory.
+  auto lock_rv = memory.Lock(0, 0);
+  EXPECT_EQ(DiscardableSharedMemory::SUCCESS, lock_rv);
+  memory.SetNow(Time::FromDoubleT(2));
+  memory.Unlock(0, 0);
+}
+
 #if defined(DISCARDABLE_SHARED_MEMORY_SHRINKING)
 TEST(DiscardableSharedMemoryTest, Shrink) {
   const uint32 kDataSize = 1024;

content/common/host_discardable_shared_memory_manager.cc

@@ -132,6 +132,8 @@ HostDiscardableSharedMemoryManager::AllocateLockedDiscardableMemory(
   scoped_ptr<base::DiscardableSharedMemory> memory(
       new base::DiscardableSharedMemory(handle));
   CHECK(memory->Map(size));
+  // Close file descriptor to avoid running out.
+  memory->Close();
   return make_scoped_ptr(new DiscardableMemoryImpl(
       memory.Pass(),
       base::Bind(
@@ -246,6 +248,11 @@ void HostDiscardableSharedMemoryManager::AllocateLockedDiscardableSharedMemory(
   bytes_allocated_ = checked_bytes_allocated.ValueOrDie();
   BytesAllocatedChanged(bytes_allocated_);
 
+#if !defined(DISCARDABLE_SHARED_MEMORY_SHRINKING)
+  // Close file descriptor to avoid running out.
+  memory->Close();
+#endif
+
   scoped_refptr<MemorySegment> segment(new MemorySegment(memory.Pass()));
   process_segments[id] = segment.get();
   segments_.push_back(segment.get());
@@ -374,6 +381,7 @@ void HostDiscardableSharedMemoryManager::ReleaseMemory(
   // Note: We intentionally leave the segment in the |segments| vector to
   // avoid reconstructing the heap. The element will be removed from the heap
   // when its last usage time is older than all other segments.
+  memory->Unmap();
   memory->Close();
 }