diff --git a/chrome/browser/chromeos/file_system_provider/operations/copy_entry.cc b/chrome/browser/chromeos/file_system_provider/operations/copy_entry.cc
index 56fd67d0a43c1c..a89cfc606c520f 100644
--- a/chrome/browser/chromeos/file_system_provider/operations/copy_entry.cc
+++ b/chrome/browser/chromeos/file_system_provider/operations/copy_entry.cc
@@ -28,6 +28,9 @@ CopyEntry::~CopyEntry() {
 }
 
 bool CopyEntry::Execute(int request_id) {
+  if (!file_system_info_.writable())
+    return false;
+
   scoped_ptr<base::DictionaryValue> values(new base::DictionaryValue);
   values->SetString("sourcePath", source_path_.AsUTF8Unsafe());
   values->SetString("targetPath", target_path_.AsUTF8Unsafe());
diff --git a/chrome/browser/chromeos/file_system_provider/operations/copy_entry_unittest.cc b/chrome/browser/chromeos/file_system_provider/operations/copy_entry_unittest.cc
index 1144a74d803407..20f75cd7a48b77 100644
--- a/chrome/browser/chromeos/file_system_provider/operations/copy_entry_unittest.cc
+++ b/chrome/browser/chromeos/file_system_provider/operations/copy_entry_unittest.cc
@@ -108,6 +108,29 @@ TEST_F(FileSystemProviderOperationsCopyEntryTest, Execute_NoListener) {
   EXPECT_FALSE(copy_entry.Execute(kRequestId));
 }
 
+TEST_F(FileSystemProviderOperationsCopyEntryTest, Execute_ReadOnly) {
+  util::LoggingDispatchEventImpl dispatcher(true /* dispatch_reply */);
+  util::StatusCallbackLog callback_log;
+
+  const ProvidedFileSystemInfo read_only_file_system_info(
+      kExtensionId,
+      kFileSystemId,
+      "" /* file_system_name */,
+      false /* writable */,
+      base::FilePath() /* mount_path */);
+
+  CopyEntry copy_entry(NULL,
+                       read_only_file_system_info,
+                       base::FilePath::FromUTF8Unsafe(kSourcePath),
+                       base::FilePath::FromUTF8Unsafe(kTargetPath),
+                       base::Bind(&util::LogStatusCallback, &callback_log));
+  copy_entry.SetDispatchEventImplForTesting(
+      base::Bind(&util::LoggingDispatchEventImpl::OnDispatchEventImpl,
+                 base::Unretained(&dispatcher)));
+
+  EXPECT_FALSE(copy_entry.Execute(kRequestId));
+}
+
 TEST_F(FileSystemProviderOperationsCopyEntryTest, OnSuccess) {
   util::LoggingDispatchEventImpl dispatcher(true /* dispatch_reply */);
   util::StatusCallbackLog callback_log;
diff --git a/chrome/browser/chromeos/file_system_provider/operations/create_directory.cc b/chrome/browser/chromeos/file_system_provider/operations/create_directory.cc
index bacd7364bf5120..77984affa1a986 100644
--- a/chrome/browser/chromeos/file_system_provider/operations/create_directory.cc
+++ b/chrome/browser/chromeos/file_system_provider/operations/create_directory.cc
@@ -31,6 +31,9 @@ CreateDirectory::~CreateDirectory() {
 }
 
 bool CreateDirectory::Execute(int request_id) {
+  if (!file_system_info_.writable())
+    return false;
+
   scoped_ptr<base::DictionaryValue> values(new base::DictionaryValue);
   values->SetString("directoryPath", directory_path_.AsUTF8Unsafe());
   values->SetBoolean("exclusive", exclusive_);
diff --git a/chrome/browser/chromeos/file_system_provider/operations/create_directory_unittest.cc b/chrome/browser/chromeos/file_system_provider/operations/create_directory_unittest.cc
index 6d1869a18b4bf9..e4f191bb91a607 100644
--- a/chrome/browser/chromeos/file_system_provider/operations/create_directory_unittest.cc
+++ b/chrome/browser/chromeos/file_system_provider/operations/create_directory_unittest.cc
@@ -115,6 +115,31 @@ TEST_F(FileSystemProviderOperationsCreateDirectoryTest, Execute_NoListener) {
   EXPECT_FALSE(create_directory.Execute(kRequestId));
 }
 
+TEST_F(FileSystemProviderOperationsCreateDirectoryTest, Execute_ReadOnly) {
+  util::LoggingDispatchEventImpl dispatcher(true /* dispatch_reply */);
+  util::StatusCallbackLog callback_log;
+
+  const ProvidedFileSystemInfo read_only_file_system_info(
+      kExtensionId,
+      kFileSystemId,
+      "" /* file_system_name */,
+      false /* writable */,
+      base::FilePath() /* mount_path */);
+
+  CreateDirectory create_directory(
+      NULL,
+      read_only_file_system_info,
+      base::FilePath::FromUTF8Unsafe(kDirectoryPath),
+      false /* exclusive */,
+      true /* recursive */,
+      base::Bind(&util::LogStatusCallback, &callback_log));
+  create_directory.SetDispatchEventImplForTesting(
+      base::Bind(&util::LoggingDispatchEventImpl::OnDispatchEventImpl,
+                 base::Unretained(&dispatcher)));
+
+  EXPECT_FALSE(create_directory.Execute(kRequestId));
+}
+
 TEST_F(FileSystemProviderOperationsCreateDirectoryTest, OnSuccess) {
   util::LoggingDispatchEventImpl dispatcher(true /* dispatch_reply */);
   util::StatusCallbackLog callback_log;
diff --git a/chrome/browser/chromeos/file_system_provider/operations/create_file.cc b/chrome/browser/chromeos/file_system_provider/operations/create_file.cc
index 9f861c78029498..27fb164a9a2c9c 100644
--- a/chrome/browser/chromeos/file_system_provider/operations/create_file.cc
+++ b/chrome/browser/chromeos/file_system_provider/operations/create_file.cc
@@ -26,6 +26,9 @@ CreateFile::~CreateFile() {
 }
 
 bool CreateFile::Execute(int request_id) {
+  if (!file_system_info_.writable())
+    return false;
+
   scoped_ptr<base::DictionaryValue> values(new base::DictionaryValue);
   values->SetString("filePath", file_path_.AsUTF8Unsafe());
 
diff --git a/chrome/browser/chromeos/file_system_provider/operations/create_file_unittest.cc b/chrome/browser/chromeos/file_system_provider/operations/create_file_unittest.cc
index 1dbce12445c432..37f77cbd8c436c 100644
--- a/chrome/browser/chromeos/file_system_provider/operations/create_file_unittest.cc
+++ b/chrome/browser/chromeos/file_system_provider/operations/create_file_unittest.cc
@@ -101,6 +101,28 @@ TEST_F(FileSystemProviderOperationsCreateFileTest, Execute_NoListener) {
   EXPECT_FALSE(create_file.Execute(kRequestId));
 }
 
+TEST_F(FileSystemProviderOperationsCreateFileTest, Execute_ReadOnly) {
+  util::LoggingDispatchEventImpl dispatcher(true /* dispatch_reply */);
+  util::StatusCallbackLog callback_log;
+
+  const ProvidedFileSystemInfo read_only_file_system_info(
+      kExtensionId,
+      kFileSystemId,
+      "" /* file_system_name */,
+      false /* writable */,
+      base::FilePath() /* mount_path */);
+
+  CreateFile create_file(NULL,
+                         read_only_file_system_info,
+                         base::FilePath::FromUTF8Unsafe(kFilePath),
+                         base::Bind(&util::LogStatusCallback, &callback_log));
+  create_file.SetDispatchEventImplForTesting(
+      base::Bind(&util::LoggingDispatchEventImpl::OnDispatchEventImpl,
+                 base::Unretained(&dispatcher)));
+
+  EXPECT_FALSE(create_file.Execute(kRequestId));
+}
+
 TEST_F(FileSystemProviderOperationsCreateFileTest, OnSuccess) {
   util::LoggingDispatchEventImpl dispatcher(true /* dispatch_reply */);
   util::StatusCallbackLog callback_log;
diff --git a/chrome/browser/chromeos/file_system_provider/operations/delete_entry.cc b/chrome/browser/chromeos/file_system_provider/operations/delete_entry.cc
index 867653c2660741..513b3fdf7362af 100644
--- a/chrome/browser/chromeos/file_system_provider/operations/delete_entry.cc
+++ b/chrome/browser/chromeos/file_system_provider/operations/delete_entry.cc
@@ -28,6 +28,9 @@ DeleteEntry::~DeleteEntry() {
 }
 
 bool DeleteEntry::Execute(int request_id) {
+  if (!file_system_info_.writable())
+    return false;
+
   scoped_ptr<base::DictionaryValue> values(new base::DictionaryValue);
   values->SetString("entryPath", entry_path_.AsUTF8Unsafe());
   values->SetBoolean("recursive", recursive_);
diff --git a/chrome/browser/chromeos/file_system_provider/operations/delete_entry_unittest.cc b/chrome/browser/chromeos/file_system_provider/operations/delete_entry_unittest.cc
index c70dc2d2f42457..9a40423918839b 100644
--- a/chrome/browser/chromeos/file_system_provider/operations/delete_entry_unittest.cc
+++ b/chrome/browser/chromeos/file_system_provider/operations/delete_entry_unittest.cc
@@ -41,7 +41,7 @@ class FileSystemProviderOperationsDeleteEntryTest : public testing::Test {
         ProvidedFileSystemInfo(kExtensionId,
                                kFileSystemId,
                                "" /* file_system_name */,
-                               false /* writable */,
+                               true /* writable */,
                                base::FilePath() /* mount_path */);
   }
 
@@ -107,6 +107,29 @@ TEST_F(FileSystemProviderOperationsDeleteEntryTest, Execute_NoListener) {
   EXPECT_FALSE(delete_entry.Execute(kRequestId));
 }
 
+TEST_F(FileSystemProviderOperationsDeleteEntryTest, Execute_ReadOnly) {
+  util::LoggingDispatchEventImpl dispatcher(true /* dispatch_reply */);
+  util::StatusCallbackLog callback_log;
+
+  const ProvidedFileSystemInfo read_only_file_system_info(
+      kExtensionId,
+      kFileSystemId,
+      "" /* file_system_name */,
+      false /* writable */,
+      base::FilePath() /* mount_path */);
+
+  DeleteEntry delete_entry(NULL,
+                           read_only_file_system_info,
+                           base::FilePath::FromUTF8Unsafe(kEntryPath),
+                           true /* recursive */,
+                           base::Bind(&util::LogStatusCallback, &callback_log));
+  delete_entry.SetDispatchEventImplForTesting(
+      base::Bind(&util::LoggingDispatchEventImpl::OnDispatchEventImpl,
+                 base::Unretained(&dispatcher)));
+
+  EXPECT_FALSE(delete_entry.Execute(kRequestId));
+}
+
 TEST_F(FileSystemProviderOperationsDeleteEntryTest, OnSuccess) {
   util::LoggingDispatchEventImpl dispatcher(true /* dispatch_reply */);
   util::StatusCallbackLog callback_log;
diff --git a/chrome/browser/chromeos/file_system_provider/operations/move_entry.cc b/chrome/browser/chromeos/file_system_provider/operations/move_entry.cc
index ec5ec7a146a491..909bb35676c3a0 100644
--- a/chrome/browser/chromeos/file_system_provider/operations/move_entry.cc
+++ b/chrome/browser/chromeos/file_system_provider/operations/move_entry.cc
@@ -28,6 +28,9 @@ MoveEntry::~MoveEntry() {
 }
 
 bool MoveEntry::Execute(int request_id) {
+  if (!file_system_info_.writable())
+    return false;
+
   scoped_ptr<base::DictionaryValue> values(new base::DictionaryValue);
   values->SetString("sourcePath", source_path_.AsUTF8Unsafe());
   values->SetString("targetPath", target_path_.AsUTF8Unsafe());
diff --git a/chrome/browser/chromeos/file_system_provider/operations/move_entry_unittest.cc b/chrome/browser/chromeos/file_system_provider/operations/move_entry_unittest.cc
index d8e1a211637c91..857cbf4fbb35fc 100644
--- a/chrome/browser/chromeos/file_system_provider/operations/move_entry_unittest.cc
+++ b/chrome/browser/chromeos/file_system_provider/operations/move_entry_unittest.cc
@@ -108,6 +108,29 @@ TEST_F(FileSystemProviderOperationsMoveEntryTest, Execute_NoListener) {
   EXPECT_FALSE(move_entry.Execute(kRequestId));
 }
 
+TEST_F(FileSystemProviderOperationsMoveEntryTest, Execute_ReadOnly) {
+  util::LoggingDispatchEventImpl dispatcher(true /* dispatch_reply */);
+  util::StatusCallbackLog callback_log;
+
+  const ProvidedFileSystemInfo read_only_file_system_info(
+      kExtensionId,
+      kFileSystemId,
+      "" /* file_system_name */,
+      false /* writable */,
+      base::FilePath() /* mount_path */);
+
+  MoveEntry move_entry(NULL,
+                       read_only_file_system_info,
+                       base::FilePath::FromUTF8Unsafe(kSourcePath),
+                       base::FilePath::FromUTF8Unsafe(kTargetPath),
+                       base::Bind(&util::LogStatusCallback, &callback_log));
+  move_entry.SetDispatchEventImplForTesting(
+      base::Bind(&util::LoggingDispatchEventImpl::OnDispatchEventImpl,
+                 base::Unretained(&dispatcher)));
+
+  EXPECT_FALSE(move_entry.Execute(kRequestId));
+}
+
 TEST_F(FileSystemProviderOperationsMoveEntryTest, OnSuccess) {
   util::LoggingDispatchEventImpl dispatcher(true /* dispatch_reply */);
   util::StatusCallbackLog callback_log;
diff --git a/chrome/browser/chromeos/file_system_provider/operations/open_file.cc b/chrome/browser/chromeos/file_system_provider/operations/open_file.cc
index 8a1a3617f8e4d4..93c930f4fed32c 100644
--- a/chrome/browser/chromeos/file_system_provider/operations/open_file.cc
+++ b/chrome/browser/chromeos/file_system_provider/operations/open_file.cc
@@ -29,6 +29,11 @@ OpenFile::~OpenFile() {
 }
 
 bool OpenFile::Execute(int request_id) {
+  if (!file_system_info_.writable() &&
+      mode_ == ProvidedFileSystemInterface::OPEN_FILE_MODE_WRITE) {
+    return false;
+  }
+
   scoped_ptr<base::DictionaryValue> values(new base::DictionaryValue);
   values->SetString("filePath", file_path_.AsUTF8Unsafe());
 
diff --git a/chrome/browser/chromeos/file_system_provider/operations/open_file_unittest.cc b/chrome/browser/chromeos/file_system_provider/operations/open_file_unittest.cc
index db3d84d96ef40d..749f40249d01e6 100644
--- a/chrome/browser/chromeos/file_system_provider/operations/open_file_unittest.cc
+++ b/chrome/browser/chromeos/file_system_provider/operations/open_file_unittest.cc
@@ -147,6 +147,48 @@ TEST_F(FileSystemProviderOperationsOpenFileTest, Execute_NoListener) {
   EXPECT_FALSE(open_file.Execute(kRequestId));
 }
 
+TEST_F(FileSystemProviderOperationsOpenFileTest, Execute_ReadOnly) {
+  util::LoggingDispatchEventImpl dispatcher(true /* dispatch_reply */);
+  CallbackLogger callback_logger;
+
+  const ProvidedFileSystemInfo read_only_file_system_info(
+      kExtensionId,
+      kFileSystemId,
+      "" /* file_system_name */,
+      false /* writable */,
+      base::FilePath() /* mount_path */);
+
+  // Opening for read on a read-only file system is allowed.
+  {
+    OpenFile open_file(NULL,
+                       read_only_file_system_info,
+                       base::FilePath::FromUTF8Unsafe(kFilePath),
+                       ProvidedFileSystemInterface::OPEN_FILE_MODE_READ,
+                       base::Bind(&CallbackLogger::OnOpenFile,
+                                  base::Unretained(&callback_logger)));
+    open_file.SetDispatchEventImplForTesting(
+        base::Bind(&util::LoggingDispatchEventImpl::OnDispatchEventImpl,
+                   base::Unretained(&dispatcher)));
+
+    EXPECT_TRUE(open_file.Execute(kRequestId));
+  }
+
+  // Opening for write on a read-only file system is forbidden and must fail.
+  {
+    OpenFile open_file(NULL,
+                       read_only_file_system_info,
+                       base::FilePath::FromUTF8Unsafe(kFilePath),
+                       ProvidedFileSystemInterface::OPEN_FILE_MODE_WRITE,
+                       base::Bind(&CallbackLogger::OnOpenFile,
+                                  base::Unretained(&callback_logger)));
+    open_file.SetDispatchEventImplForTesting(
+        base::Bind(&util::LoggingDispatchEventImpl::OnDispatchEventImpl,
+                   base::Unretained(&dispatcher)));
+
+    EXPECT_FALSE(open_file.Execute(kRequestId));
+  }
+}
+
 TEST_F(FileSystemProviderOperationsOpenFileTest, OnSuccess) {
   util::LoggingDispatchEventImpl dispatcher(true /* dispatch_reply */);
   CallbackLogger callback_logger;
diff --git a/chrome/browser/chromeos/file_system_provider/operations/truncate.cc b/chrome/browser/chromeos/file_system_provider/operations/truncate.cc
index c7537a46aab256..f167aef1a3be7e 100644
--- a/chrome/browser/chromeos/file_system_provider/operations/truncate.cc
+++ b/chrome/browser/chromeos/file_system_provider/operations/truncate.cc
@@ -28,6 +28,9 @@ Truncate::~Truncate() {
 }
 
 bool Truncate::Execute(int request_id) {
+  if (!file_system_info_.writable())
+    return false;
+
   scoped_ptr<base::DictionaryValue> values(new base::DictionaryValue);
   values->SetString("filePath", file_path_.AsUTF8Unsafe());
   values->SetDouble("length", length_);
diff --git a/chrome/browser/chromeos/file_system_provider/operations/truncate_unittest.cc b/chrome/browser/chromeos/file_system_provider/operations/truncate_unittest.cc
index 66e2adcbede4aa..1ba6a14c29f743 100644
--- a/chrome/browser/chromeos/file_system_provider/operations/truncate_unittest.cc
+++ b/chrome/browser/chromeos/file_system_provider/operations/truncate_unittest.cc
@@ -108,6 +108,29 @@ TEST_F(FileSystemProviderOperationsTruncateTest, Execute_NoListener) {
   EXPECT_FALSE(truncate.Execute(kRequestId));
 }
 
+TEST_F(FileSystemProviderOperationsTruncateTest, Execute_ReadOnly) {
+  util::LoggingDispatchEventImpl dispatcher(false /* dispatch_reply */);
+  util::StatusCallbackLog callback_log;
+
+  const ProvidedFileSystemInfo read_only_file_system_info(
+      kExtensionId,
+      kFileSystemId,
+      "" /* file_system_name */,
+      false /* writable */,
+      base::FilePath() /* mount_path */);
+
+  Truncate truncate(NULL,
+                    file_system_info_,
+                    base::FilePath::FromUTF8Unsafe(kFilePath),
+                    kTruncateLength,
+                    base::Bind(&util::LogStatusCallback, &callback_log));
+  truncate.SetDispatchEventImplForTesting(
+      base::Bind(&util::LoggingDispatchEventImpl::OnDispatchEventImpl,
+                 base::Unretained(&dispatcher)));
+
+  EXPECT_FALSE(truncate.Execute(kRequestId));
+}
+
 TEST_F(FileSystemProviderOperationsTruncateTest, OnSuccess) {
   util::LoggingDispatchEventImpl dispatcher(true /* dispatch_reply */);
   util::StatusCallbackLog callback_log;
diff --git a/chrome/test/data/extensions/api_test/file_system_provider/test_util/test_util.js b/chrome/test/data/extensions/api_test/file_system_provider/test_util/test_util.js
index 047e4c89a5c061..2ce6ce00d9c289 100644
--- a/chrome/test/data/extensions/api_test/file_system_provider/test_util/test_util.js
+++ b/chrome/test/data/extensions/api_test/file_system_provider/test_util/test_util.js
@@ -69,7 +69,8 @@ test_util.mountFileSystem = function(callback) {
   chrome.fileSystemProvider.mount(
       {
         fileSystemId: test_util.FILE_SYSTEM_ID,
-        displayName: test_util.FILE_SYSTEM_NAME
+        displayName: test_util.FILE_SYSTEM_NAME,
+        writable: true
       },
       function() {
         var volumeId =