Revert "Unmap unpinned ashmem regions."

This reverts r232081 since it was a temporary workaround that was needed until
Telemetry supports unpinned ashmem purging before doing memory measurements
(which was added by r235115).

BUG=311633,317626
TBR=willchan

Review URL: https://codereview.chromium.org/64743006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235143 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 4 insertions, 26 deletions

diff --git a/base/memory/discardable_memory_android.cc b/base/memory/discardable_memory_android.cc
index c75d7c1..3850439 100644
--- a/base/memory/discardable_memory_android.cc
+++ b/base/memory/discardable_memory_android.cc
@@ -83,6 +83,7 @@ LockDiscardableMemoryStatus LockAshmemRegion(int fd,
                                              size_t size,
                                              const void* address) {
   const int result = ashmem_pin_region(fd, off, size);
+  DCHECK_EQ(0, mprotect(address, size, PROT_READ | PROT_WRITE));
   return result == ASHMEM_WAS_PURGED ?
       DISCARDABLE_MEMORY_PURGED : DISCARDABLE_MEMORY_SUCCESS;
 }
@@ -91,6 +92,8 @@ bool UnlockAshmemRegion(int fd, size_t off, size_t size, const void* address) {
   const int failed = ashmem_unpin_region(fd, off, size);
   if (failed)
     DLOG(ERROR) << "Failed to unpin memory.";
+  // This allows us to catch accesses to unlocked memory.
+  DCHECK_EQ(0, mprotect(address, size, PROT_NONE));
   return !failed;
 }
 
@@ -110,45 +113,20 @@ class DiscardableMemoryAndroid : public DiscardableMemory {
 
   // DiscardableMemory:
   virtual LockDiscardableMemoryStatus Lock() OVERRIDE {
-    if (!memory_ && !MapRegion())
-      return DISCARDABLE_MEMORY_FAILED;
     return LockAshmemRegion(fd_, 0, size_, memory_);
   }
 
   virtual void Unlock() OVERRIDE {
-    UnmapRegion();
     UnlockAshmemRegion(fd_, 0, size_, memory_);
   }
 
   virtual void* Memory() const OVERRIDE {
-    DCHECK(memory_) << "Trying to access unmapped memory";
     return memory_;
   }
 
  private:
-  // TODO(pliard): http://crbug.com/311633. Remove the two methods below once
-  // memory measurement infrastructure supports unpinned ashmem purging.
-  bool MapRegion() {
-    DCHECK(!memory_) << "Region already mapped";
-    void* const address = mmap(
-        NULL, size_, PROT_READ | PROT_WRITE, MAP_SHARED, fd_, 0);
-    if (address == MAP_FAILED) {
-      DPLOG(ERROR) << "Failed to map memory.";
-      return false;
-    }
-    memory_ = address;
-    return true;
-  }
-
-  void UnmapRegion() {
-    DCHECK(memory_) << "Region already unmapped";
-    if (munmap(memory_, size_) == -1)
-      DPLOG(ERROR) << "Failed to unmap memory.";
-    memory_ = NULL;
-  }
-
   const int fd_;
-  void* memory_;
+  void* const memory_;
   const size_t size_;
 
   DISALLOW_COPY_AND_ASSIGN(DiscardableMemoryAndroid);