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Commit 9415ba0a authored by JW Wang's avatar JW Wang
Browse files

Populate APK files using hard links (2/n) 

This is an effort to improve the storage usage of RollbackManager.

When committing a rollback, the apk/apex files will be deleted after
the install session is committed successfully. We can use hard links
to effectively transfer the files to PackageInstaller to avoid copy.

Bug: 168562373
Test: atest RollbackTest StagedRollbackTest

Change-Id: I749a17d769d1845bb0f9b34c8757b69b40b516f9
parent d6395c51

core/java/android/content/pm/IPackageInstallerSession.aidl

+1 −0
Original line number Diff line number Diff line
@@ -33,6 +33,7 @@ interface IPackageInstallerSession { 
    ParcelFileDescriptor openRead(String name);



    void write(String name, long offsetBytes, long lengthBytes, in ParcelFileDescriptor fd);

    void stageViaHardLink(String target);



    void addChecksums(String name, in Checksum[] checksums);

core/java/android/content/pm/PackageInstaller.java

+25 −0
Original line number Diff line number Diff line
@@ -1048,6 +1048,31 @@ public class PackageInstaller { 
            }

        }



        /**

         * Populate an APK file by creating a hard link to avoid the need to copy.

         * <p>

         * Note this API is used by RollbackManager only and can only be called from system_server.

         * {@code target} will be relabeled if link is created successfully. RollbackManager has

         * to delete {@code target} when the session is committed successfully to avoid SELinux

         * label conflicts.

         * <p>

         * Note No more bytes should be written to the file once the link is created successfully.

         *

         * @param target the path of the link target

         *

         * @hide

         */

        public void stageViaHardLink(String target) throws IOException {

            try {

                mSession.stageViaHardLink(target);

            } catch (RuntimeException e) {

                ExceptionUtils.maybeUnwrapIOException(e);

                throw e;

            } catch (RemoteException e) {

                throw e.rethrowFromSystemServer();

            }

        }



        /**

         * Ensure that any outstanding data for given stream has been committed

         * to disk. This is only valid for streams returned from

services/core/java/com/android/server/pm/PackageInstallerSession.java

+26 −0
Original line number Diff line number Diff line
@@ -110,6 +110,7 @@ import android.os.ParcelableException; 
import android.os.Process;

import android.os.RemoteException;

import android.os.RevocableFileDescriptor;

import android.os.SELinux;

import android.os.SystemProperties;

import android.os.UserHandle;

import android.os.incremental.IStorageHealthListener;
@@ -1092,6 +1093,31 @@ public class PackageInstallerSession extends IPackageInstallerSession.Stub { 
        }

    }



    @Override

    public void stageViaHardLink(String path) {

        final int callingUid = Binder.getCallingUid();

        if (callingUid != Process.SYSTEM_UID) {

            throw new SecurityException("link() can only be run by the system");

        }



        try {

            final File target = new File(path);

            final File source = new File(stageDir, target.getName());

            try {

                Os.link(path, source.getAbsolutePath());

                // Grant READ access for APK to be read successfully

                Os.chmod(source.getAbsolutePath(), 0644);

            } catch (ErrnoException e) {

                e.rethrowAsIOException();

            }

            if (!SELinux.restorecon(source)) {

                throw new IOException("Can't relabel file: " + source);

            }

        } catch (IOException e) {

            throw ExceptionUtils.wrap(e);

        }

    }



    private ParcelFileDescriptor openTargetInternal(String path, int flags, int mode)

            throws IOException, ErrnoException {

        // TODO: this should delegate to DCS so the system process avoids

services/core/java/com/android/server/rollback/Rollback.java

+12 −3
Original line number Diff line number Diff line
@@ -581,9 +581,18 @@ class Rollback { 
                            ParcelFileDescriptor.MODE_READ_ONLY)) {

                        final long token = Binder.clearCallingIdentity();

                        try {

                            boolean fallbackToCopy = false;

                            try {

                                // Populate apk/apex files using hard links to avoid copy

                                session.stageViaHardLink(packageCodePath.getAbsolutePath());

                            } catch (Exception ignore) {

                                fallbackToCopy = true;

                            }

                            if (fallbackToCopy) {

                                session.write(packageCodePath.getName(), 0,

                                        packageCodePath.length(),

                                        fd);

                            }

                        } finally {

                            Binder.restoreCallingIdentity(token);

                        }