Revert "libsnapshot: Implement OnlineKernelSnapshotWriter::OpenReader."

This reverts commit 39f250896a9ae991a6e80a4231954fbae8a8d125.

Reason for revert: b/169981170, update crash for droidfooders.

Change-Id: I6a3d096df3174596d36195bf59fa8fbc88c982d0
diff --git a/fs_mgr/libsnapshot/Android.bp b/fs_mgr/libsnapshot/Android.bp
index 046ea74..a3384e4 100644
--- a/fs_mgr/libsnapshot/Android.bp
+++ b/fs_mgr/libsnapshot/Android.bp
@@ -74,7 +74,6 @@
         "android/snapshot/snapshot.proto",
         "device_info.cpp",
         "snapshot.cpp",
-        "snapshot_reader.cpp",
         "snapshot_stats.cpp",
         "snapshot_stub.cpp",
         "snapshot_metadata_updater.cpp",
diff --git a/fs_mgr/libsnapshot/snapshot.cpp b/fs_mgr/libsnapshot/snapshot.cpp
index b672d0e..8ac2f83 100644
--- a/fs_mgr/libsnapshot/snapshot.cpp
+++ b/fs_mgr/libsnapshot/snapshot.cpp
@@ -44,7 +44,6 @@
 #include "device_info.h"
 #include "partition_cow_creator.h"
 #include "snapshot_metadata_updater.h"
-#include "snapshot_reader.h"
 #include "utility.h"
 
 namespace android {
diff --git a/fs_mgr/libsnapshot/snapshot_reader.cpp b/fs_mgr/libsnapshot/snapshot_reader.cpp
deleted file mode 100644
index 0d47468..0000000
--- a/fs_mgr/libsnapshot/snapshot_reader.cpp
+++ /dev/null
@@ -1,77 +0,0 @@
-//
-// Copyright (C) 2020 The Android Open Source Project
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//      http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-//
-
-#include <ext4_utils/ext4_utils.h>
-
-#include "snapshot_reader.h"
-
-namespace android {
-namespace snapshot {
-
-// Not supported.
-bool ReadOnlyFileDescriptor::Open(const char*, int, mode_t) {
-    errno = EINVAL;
-    return false;
-}
-
-bool ReadOnlyFileDescriptor::Open(const char*, int) {
-    errno = EINVAL;
-    return false;
-}
-
-ssize_t ReadOnlyFileDescriptor::Write(const void*, size_t) {
-    errno = EINVAL;
-    return false;
-}
-
-bool ReadOnlyFileDescriptor::BlkIoctl(int, uint64_t, uint64_t, int*) {
-    errno = EINVAL;
-    return false;
-}
-
-ReadFdFileDescriptor::ReadFdFileDescriptor(android::base::unique_fd&& fd) : fd_(std::move(fd)) {}
-
-ssize_t ReadFdFileDescriptor::Read(void* buf, size_t count) {
-    return read(fd_.get(), buf, count);
-}
-
-off64_t ReadFdFileDescriptor::Seek(off64_t offset, int whence) {
-    return lseek(fd_.get(), offset, whence);
-}
-
-uint64_t ReadFdFileDescriptor::BlockDevSize() {
-    return get_block_device_size(fd_.get());
-}
-
-bool ReadFdFileDescriptor::Close() {
-    fd_ = {};
-    return true;
-}
-
-bool ReadFdFileDescriptor::IsSettingErrno() {
-    return true;
-}
-
-bool ReadFdFileDescriptor::IsOpen() {
-    return fd_ >= 0;
-}
-
-bool ReadFdFileDescriptor::Flush() {
-    return true;
-}
-
-}  // namespace snapshot
-}  // namespace android
diff --git a/fs_mgr/libsnapshot/snapshot_reader.h b/fs_mgr/libsnapshot/snapshot_reader.h
deleted file mode 100644
index 1f2ffe2..0000000
--- a/fs_mgr/libsnapshot/snapshot_reader.h
+++ /dev/null
@@ -1,50 +0,0 @@
-//
-// Copyright (C) 2020 The Android Open Source Project
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//      http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-//
-
-#pragma once
-
-#include <android-base/file.h>
-#include <payload_consumer/file_descriptor.h>
-
-namespace android {
-namespace snapshot {
-
-class ReadOnlyFileDescriptor : public chromeos_update_engine::FileDescriptor {
-  public:
-    bool Open(const char* path, int flags, mode_t mode) override;
-    bool Open(const char* path, int flags) override;
-    ssize_t Write(const void* buf, size_t count) override;
-    bool BlkIoctl(int request, uint64_t start, uint64_t length, int* result) override;
-};
-
-class ReadFdFileDescriptor : public ReadOnlyFileDescriptor {
-  public:
-    explicit ReadFdFileDescriptor(android::base::unique_fd&& fd);
-
-    ssize_t Read(void* buf, size_t count) override;
-    off64_t Seek(off64_t offset, int whence) override;
-    uint64_t BlockDevSize() override;
-    bool Close() override;
-    bool IsSettingErrno() override;
-    bool IsOpen() override;
-    bool Flush() override;
-
-  private:
-    android::base::unique_fd fd_;
-};
-
-}  // namespace snapshot
-}  // namespace android
diff --git a/fs_mgr/libsnapshot/snapshot_writer.cpp b/fs_mgr/libsnapshot/snapshot_writer.cpp
index 584f15e..1958f18 100644
--- a/fs_mgr/libsnapshot/snapshot_writer.cpp
+++ b/fs_mgr/libsnapshot/snapshot_writer.cpp
@@ -19,12 +19,10 @@
 #include <android-base/file.h>
 #include <android-base/logging.h>
 #include <payload_consumer/file_descriptor.h>
-#include "snapshot_reader.h"
 
 namespace android {
 namespace snapshot {
 
-using android::base::unique_fd;
 using chromeos_update_engine::FileDescriptor;
 
 ISnapshotWriter::ISnapshotWriter(const CowOptions& options) : ICowWriter(options) {}
@@ -85,12 +83,8 @@
 }
 
 std::unique_ptr<FileDescriptor> OnlineKernelSnapshotWriter::OpenReader() {
-    unique_fd fd(dup(snapshot_fd_.get()));
-    if (fd < 0) {
-        PLOG(ERROR) << "dup2 failed in OpenReader";
-        return nullptr;
-    }
-    return std::make_unique<ReadFdFileDescriptor>(std::move(fd));
+    LOG(ERROR) << "OnlineKernelSnapshotWriter::OpenReader not yet implemented";
+    return nullptr;
 }
 
 }  // namespace snapshot