Better mount-point management

This adds the option to watch individual mount-points for mount and
umount events from the kernel.

(this is a manual cherry-pick of 34a562c2f55d391 from dev)

Change-Id: Icba453ef4b5ecb7499b6a5df028184737f4610cc
Reviewed-by: Dominik Holland <dominik.holland@qt.io>

5 files changed, 330 insertions, 57 deletions

diff --git a/src/common-lib/common-lib.pro b/src/common-lib/common-lib.pro
index ed98d0ad..f240bbef 100644
--- a/src/common-lib/common-lib.pro
+++ b/src/common-lib/common-lib.pro
@@ -25,6 +25,7 @@ contains(DEFINES, "AM_USE_STACKWALKER"):include($$SOURCE_DIR/3rdparty/stackwalke
 
 SOURCES += \
     exception.cpp \
+    filesystemmountwatcher.cpp \
     utilities.cpp \
     qtyaml.cpp \
     startuptimer.cpp \
@@ -42,6 +43,7 @@ HEADERS += \
     global.h \
     error.h \
     exception.h \
+    filesystemmountwatcher.h \
     utilities.h \
     qtyaml.h \
     startuptimer.h \
diff --git a/src/common-lib/filesystemmountwatcher.cpp b/src/common-lib/filesystemmountwatcher.cpp
new file mode 100644
index 00000000..9b63de71
--- /dev/null
+++ b/src/common-lib/filesystemmountwatcher.cpp
@@ -0,0 +1,251 @@
+/****************************************************************************
+**
+** Copyright (C) 2021 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the Qt Application Manager.
+**
+** $QT_BEGIN_LICENSE:LGPL-QTAS$
+** Commercial License Usage
+** Licensees holding valid commercial Qt Automotive Suite licenses may use
+** this file in accordance with the commercial license agreement provided
+** with the Software or, alternatively, in accordance with the terms
+** contained in a written agreement between you and The Qt Company.  For
+** licensing terms and conditions see https://www.qt.io/terms-conditions.
+** For further information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+** SPDX-License-Identifier: LGPL-3.0
+**
+****************************************************************************/
+
+#include <QSocketNotifier>
+#include <QFileSystemWatcher>
+
+#if defined(Q_OS_MACOS) || defined(Q_OS_IOS)
+#  include <unistd.h>
+#  include <sys/statvfs.h>
+#  include <sys/mount.h>
+#elif defined(Q_OS_LINUX)
+#  include <mntent.h>
+#endif
+#include <qplatformdefs.h>
+
+#include "filesystemmountwatcher.h"
+
+QT_BEGIN_NAMESPACE_AM
+
+
+class FileSystemMountWatcherPrivate
+{
+public:
+    FileSystemMountWatcherPrivate()
+    {
+#if defined(Q_OS_LINUX)
+        if (s_mountTabFile.isEmpty()) {
+            s_mountTabFile = "/proc/self/mounts";;
+
+            m_procMountsFd = QT_OPEN(s_mountTabFile.constData(), O_RDONLY);
+            if (m_procMountsFd >= 0) {
+                m_procMountsNotifier = new QSocketNotifier(m_procMountsFd, QSocketNotifier::Exception);
+                QObject::connect(m_procMountsNotifier, &QSocketNotifier::activated,
+                                 [this]() { mountsChanged(); });
+            }
+        } else {
+            m_autoTestMountTabWatcher = new QFileSystemWatcher({ QString::fromLocal8Bit(s_mountTabFile) });
+            QObject::connect(m_autoTestMountTabWatcher, &QFileSystemWatcher::fileChanged,
+                             [this]() { mountsChanged(); });
+        }
+#endif
+    }
+
+    ~FileSystemMountWatcherPrivate()
+    {
+        delete m_autoTestMountTabWatcher;
+        delete m_procMountsNotifier;
+        if (m_procMountsFd >= 0)
+            QT_CLOSE(m_procMountsFd);
+    }
+
+    bool add(FileSystemMountWatcher *watcher, const QString &mountPoint)
+    {
+        if ((!m_procMountsNotifier && !m_autoTestMountTabWatcher) || !watcher || mountPoint.isEmpty())
+            return false;
+
+        m_mountPoints.insert(mountPoint, watcher);
+
+        if (m_mountPoints.size() == 1)
+            m_mounts = currentMountPoints(); // we need to know from where we started
+        return true;
+    }
+
+    bool remove(FileSystemMountWatcher *watcher, const QString &mountPoint)
+    {
+        if ((!m_procMountsNotifier && !m_autoTestMountTabWatcher) || !watcher || mountPoint.isEmpty())
+            return false;
+
+        m_mountPoints.remove(mountPoint, watcher);
+        return true;
+    }
+
+    void attach()
+    {
+        m_ref.ref();
+    }
+
+    bool detach(FileSystemMountWatcher *watcher)
+    {
+        for (auto it = m_mountPoints.begin(); it != m_mountPoints.end(); ) {
+            if (it.value() == watcher)
+                it = m_mountPoints.erase(it);
+            else
+                ++it;
+        }
+        return !m_ref.deref();
+    }
+
+    static QMultiMap<QString, QString> currentMountPoints()
+    {
+        QMultiMap<QString, QString> result;
+#if defined(Q_OS_WIN)
+        return result; // no mounts on Windows
+
+#elif defined(Q_OS_MACOS) || defined(Q_OS_IOS)
+        struct statfs *sfs = nullptr;
+        int count = getmntinfo(&sfs, MNT_NOWAIT);
+
+        for (int i = 0; i < count; ++i, ++sfs) {
+            result.insert(QString::fromLocal8Bit(sfs->f_mntonname), QString::fromLocal8Bit(sfs->f_mntfromname));
+        }
+#else
+        FILE *pm = fopen(s_mountTabFile.constData(), "r");
+        if (!pm)
+            return result;
+
+#  if defined(Q_OS_ANDROID)
+        while (struct mntent *mntPtr = getmntent(pm)) {
+            result.insert(QString::fromLocal8Bit(mntPtr->mnt_dir),
+                          QString::fromLocal8Bit(mntPtr->mnt_fsname));
+        }
+#  else
+        static const int pathMax = static_cast<int>(pathconf("/", _PC_PATH_MAX)) * 2 + 1024;  // quite big, but better be safe than sorry
+        QScopedArrayPointer<char> strBuf(new char[pathMax]);
+        struct mntent mntBuf;
+
+        while (getmntent_r(pm, &mntBuf, strBuf.data(), pathMax - 1)) {
+            result.insert(QString::fromLocal8Bit(mntBuf.mnt_dir),
+                          QString::fromLocal8Bit(mntBuf.mnt_fsname));
+        }
+#  endif
+        fclose(pm);
+#endif
+
+        return result;
+    }
+
+    void mountsChanged()
+    {
+        if (m_mountPoints.isEmpty())
+            return;
+
+        auto newMounts = currentMountPoints();
+
+        for (auto it = m_mountPoints.cbegin(); it != m_mountPoints.cend(); ++it) {
+            const QString mp = it.key();
+            bool isMounted = newMounts.contains(mp);
+            bool wasMounted = m_mounts.contains(mp);
+
+            if (isMounted != wasMounted)
+                emit it.value()->mountChanged(mp, newMounts.value(mp));
+        }
+
+        m_mounts = newMounts;
+    }
+
+private:
+    QAtomicInt m_ref;
+
+    static QByteArray s_mountTabFile;
+
+    int m_procMountsFd = -1;
+    QSocketNotifier *m_procMountsNotifier = nullptr;
+    QFileSystemWatcher *m_autoTestMountTabWatcher = nullptr;
+    QMultiMap<QString, FileSystemMountWatcher *> m_mountPoints;
+    QMultiMap<QString, QString> m_mounts;
+
+    friend class FileSystemMountWatcher;
+};
+
+QByteArray FileSystemMountWatcherPrivate::s_mountTabFile;
+
+
+FileSystemMountWatcherPrivate *FileSystemMountWatcher::d = nullptr;
+
+FileSystemMountWatcher::FileSystemMountWatcher(QObject *parent)
+    : QObject(parent)
+{
+    if (!d)
+        d = new FileSystemMountWatcherPrivate();
+    d->attach();
+}
+
+FileSystemMountWatcher::~FileSystemMountWatcher()
+{
+    if (d->detach(this)) {
+        delete d;
+        d = nullptr;
+    }
+}
+
+QMultiMap<QString, QString> FileSystemMountWatcher::currentMountPoints()
+{
+    // if we have an active cache, then use it
+    if (d && d->m_procMountsNotifier)
+        return d->m_mounts;
+    return FileSystemMountWatcherPrivate::currentMountPoints();
+}
+
+void FileSystemMountWatcher::addMountPoint(const QString &directory)
+{
+    d->add(this, directory);
+}
+
+void FileSystemMountWatcher::removeMountPoint(const QString &directory)
+{
+    d->remove(this, directory);
+}
+
+bool FileSystemMountWatcher::setMountTabFileForTesting(const QString &mtabFile)
+{
+    if (d)
+        return false; // too late
+#if defined(Q_OS_LINUX)
+    FileSystemMountWatcherPrivate::s_mountTabFile = mtabFile.toLocal8Bit();
+    return true;
+#else
+    Q_UNUSED(mtabFile)
+    return false;
+#endif
+}
+
+QT_END_NAMESPACE_AM
diff --git a/src/common-lib/filesystemmountwatcher.h b/src/common-lib/filesystemmountwatcher.h
new file mode 100644
index 00000000..4062f46f
--- /dev/null
+++ b/src/common-lib/filesystemmountwatcher.h
@@ -0,0 +1,75 @@
+/****************************************************************************
+**
+** Copyright (C) 2021 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the Qt Application Manager.
+**
+** $QT_BEGIN_LICENSE:LGPL-QTAS$
+** Commercial License Usage
+** Licensees holding valid commercial Qt Automotive Suite licenses may use
+** this file in accordance with the commercial license agreement provided
+** with the Software or, alternatively, in accordance with the terms
+** contained in a written agreement between you and The Qt Company.  For
+** licensing terms and conditions see https://www.qt.io/terms-conditions.
+** For further information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+** SPDX-License-Identifier: LGPL-3.0
+**
+****************************************************************************/
+
+#pragma once
+
+#include <QObject>
+#include <QMultiMap>
+#include <QtAppManCommon/global.h>
+
+QT_BEGIN_NAMESPACE_AM
+
+class FileSystemMountWatcherPrivate;
+
+class FileSystemMountWatcher : public QObject
+{
+    Q_OBJECT
+
+public:
+    FileSystemMountWatcher(QObject *parent = nullptr);
+    ~FileSystemMountWatcher();
+
+    static QMultiMap<QString, QString> currentMountPoints();
+
+    void addMountPoint(const QString &directory);
+    void removeMountPoint(const QString &directory);
+
+    // Auto-test API, only functional on Linux. Needs to be called before constructor:
+    static bool setMountTabFileForTesting(const QString &mtabFile);
+
+Q_SIGNALS:
+    void mountChanged(const QString &mountPoint, const QString &device);
+
+private:
+    static FileSystemMountWatcherPrivate *d;
+};
+
+QT_END_NAMESPACE_AM
diff --git a/src/common-lib/utilities.cpp b/src/common-lib/utilities.cpp
index eeee57c3..41e1535a 100644
--- a/src/common-lib/utilities.cpp
+++ b/src/common-lib/utilities.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2019 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Copyright (C) 2019 Luxoft Sweden AB
 ** Copyright (C) 2018 Pelagicore AG
 ** Contact: https://www.qt.io/licensing/
@@ -63,19 +63,7 @@
 #  include <tlhelp32.h>
 #elif defined(Q_OS_MACOS) || defined(Q_OS_IOS)
 #  include <unistd.h>
-#  include <sys/mount.h>
-#  include <sys/statvfs.h>
 #  include <sys/sysctl.h>
-#else
-#  include <mntent.h>
-#  include <sys/stat.h>
-#  if defined(Q_OS_ANDROID)
-#    include <sys/vfs.h>
-#    define statvfs statfs
-#  else
-#    include <sys/statvfs.h>
-#  endif
-#  include <qplatformdefs.h>
 #endif
 
 QT_BEGIN_NAMESPACE_AM
@@ -142,46 +130,6 @@ YamlFormat checkYamlFormat(const QVector<QVariant> &docs, int numberOfDocuments,
     return actualFormatTypeAndVersion;
 }
 
-QMultiMap<QString, QString> mountedDirectories()
-{
-    QMultiMap<QString, QString> result;
-#if defined(Q_OS_WIN)
-    return result; // no mounts on Windows
-
-#elif defined(Q_OS_MACOS) || defined(Q_OS_IOS)
-    struct statfs *sfs = nullptr;
-    int count = getmntinfo(&sfs, MNT_NOWAIT);
-
-    for (int i = 0; i < count; ++i, ++sfs) {
-        result.insert(QString::fromLocal8Bit(sfs->f_mntonname),
-                      QString::fromLocal8Bit(sfs->f_mntfromname));
-    }
-#else
-    FILE *pm = fopen("/proc/self/mounts", "r");
-    if (!pm)
-        return result;
-
-#  if defined(Q_OS_ANDROID)
-    while (struct mntent *mntPtr = getmntent(pm)) {
-        result.insert(QString::fromLocal8Bit(mntPtr->mnt_dir),
-                      QString::fromLocal8Bit(mntPtr->mnt_fsname));
-    }
-#  else
-    int pathMax = static_cast<int>(pathconf("/", _PC_PATH_MAX)) * 2 + 1024;  // quite big, but better be safe than sorry
-    QScopedArrayPointer<char> strBuf(new char[pathMax]);
-    struct mntent mntBuf;
-
-    while (getmntent_r(pm, &mntBuf, strBuf.data(), pathMax - 1)) {
-        result.insert(QString::fromLocal8Bit(mntBuf.mnt_dir),
-                      QString::fromLocal8Bit(mntBuf.mnt_fsname));
-    }
-#  endif
-    fclose(pm);
-#endif
-
-    return result;
-}
-
 bool safeRemove(const QString &path, RecursiveOperationType type)
 {
    static const QFileDevice::Permissions fullAccess =
diff --git a/src/common-lib/utilities.h b/src/common-lib/utilities.h
index 0d51fc6f..fa99f90f 100644
--- a/src/common-lib/utilities.h
+++ b/src/common-lib/utilities.h
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2019 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Copyright (C) 2019 Luxoft Sweden AB
 ** Copyright (C) 2018 Pelagicore AG
 ** Contact: https://www.qt.io/licensing/
@@ -46,7 +46,6 @@
 #include <QVector>
 #include <QPair>
 #include <QByteArray>
-#include <QMultiMap>
 #include <QVariant>
 #include <QString>
 #include <QUrl>
@@ -106,8 +105,6 @@ inline QString toAbsoluteFilePath(const QString &path, const QString &baseDir =
 */
 void recursiveMergeVariantMap(QVariantMap &into, const QVariantMap &from);
 
-QMultiMap<QString, QString> mountedDirectories();
-
 enum class RecursiveOperationType
 {
     EnterDirectory,