base: Introduce SharedMemoryTracker for POSIX (but not macOS)

base/memory/shared_memory_posix.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 "base/memory/shared_memory.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #include <stddef.h>
 #include <sys/mman.h>
 #include <sys/stat.h>
 #include <unistd.h>
 
 #include "base/files/file_util.h"
 #include "base/files/scoped_file.h"
 #include "base/logging.h"
 #include "base/memory/shared_memory_helper.h"
+#include "base/memory/shared_memory_tracker.h"
 #include "base/posix/eintr_wrapper.h"
 #include "base/posix/safe_strerror.h"
 #include "base/process/process_metrics.h"
 #include "base/scoped_generic.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/threading/thread_restrictions.h"
+#include "base/trace_event/trace_event.h"
 #include "build/build_config.h"
 
 #if defined(OS_ANDROID)
 #include "base/os_compat_android.h"
 #include "third_party/ashmem/ashmem.h"
 #endif
 
 namespace base {
 
 SharedMemory::SharedMemory()
@@ skipping 242 matching lines @@
     bytes = ashmem_bytes;
   }
 #endif
 
   memory_ = mmap(NULL, bytes, PROT_READ | (read_only_ ? 0 : PROT_WRITE),
                  MAP_SHARED, mapped_file_, offset);
 
   bool mmap_succeeded = memory_ != (void*)-1 && memory_ != NULL;
   if (mmap_succeeded) {
     mapped_size_ = bytes;
-    DCHECK_EQ(0U, reinterpret_cast<uintptr_t>(memory_) &
-        (SharedMemory::MAP_MINIMUM_ALIGNMENT - 1));
+    DCHECK_EQ(0U,
+              reinterpret_cast<uintptr_t>(memory_) &
+                  (SharedMemory::MAP_MINIMUM_ALIGNMENT - 1));
+    SharedMemoryTracker::GetInstance()->IncrementMemoryUsage(*this);
   } else {
     memory_ = NULL;
   }
 
   return mmap_succeeded;
 }
 
 bool SharedMemory::Unmap() {
   if (memory_ == NULL)
     return false;
 
   munmap(memory_, mapped_size_);
+  SharedMemoryTracker::GetInstance()->DecrementMemoryUsage(*this);
   memory_ = NULL;
   mapped_size_ = 0;
   return true;
 }
 
 SharedMemoryHandle SharedMemory::handle() const {
   return FileDescriptor(mapped_file_, false);
 }
 
 SharedMemoryHandle SharedMemory::TakeHandle() {
@@ skipping 73 matching lines @@
   new_handle->auto_close = true;
 
   if (close_self) {
     Unmap();
     Close();
   }
 
   return true;
 }
 
+bool SharedMemory::GetUniqueId(SharedMemory::UniqueId* id) const {
+  // This function is called just after mmap. fstat is a system call that might
+  // cause I/O. It's safe to call fstat here because mmap for shared memory is
+  // called in two cases:
+  // 1) To handle file-mapped memory
+  // 2) To handle annonymous shared memory
+  // In 1), I/O is already permitted. In 2), the backend is on page cache and
+  // fstat doesn't cause I/O access to the disk. See the discussion at
+  // crbug.com/604726#c41.
+  base::ThreadRestrictions::ScopedAllowIO allow_io;
+  struct stat file_stat;
+  if (HANDLE_EINTR(::fstat(static_cast<int>(handle().fd), &file_stat)) != 0)
+    return false;
+  id->first = file_stat.st_dev;
+  id->second = file_stat.st_ino;
+  return true;
+}
+
 }  // namespace base