Fix clang-tidy performance warnings in system/vold.

* Use const reference type for for-loop index variables
  to avoid unnecessary copy.

Bug: 30413223
Change-Id: Id4d980ae8afec1374fc3be0b23f1c6a39bff86e0
Test: build with WITH_TIDY=1

Disk.cpp

@@ -106,7 +106,7 @@ std::shared_ptr<VolumeBase> Disk::findVolume(const std::string& id) {
 }
 
 void Disk::listVolumes(VolumeBase::Type type, std::list<std::string>& list) {
-    for (auto vol : mVolumes) {
+    for (const auto& vol : mVolumes) {
         if (vol->getType() == type) {
             list.push_back(vol->getId());
         }
@@ -179,7 +179,7 @@ void Disk::createPrivateVolume(dev_t device, const std::string& partGuid) {
 }
 
 void Disk::destroyAllVolumes() {
-    for (auto vol : mVolumes) {
+    for (const auto& vol : mVolumes) {
         vol->destroy();
     }
     mVolumes.clear();
@@ -268,7 +268,7 @@ status_t Disk::readPartitions() {
 
     Table table = Table::kUnknown;
     bool foundParts = false;
-    for (auto line : output) {
+    for (const auto& line : output) {
         char* cline = (char*) line.c_str();
         char* token = strtok(cline, kSgdiskToken);
         if (token == nullptr) continue;
@@ -333,7 +333,7 @@ status_t Disk::readPartitions() {
 }
 
 status_t Disk::unmountAll() {
-    for (auto vol : mVolumes) {
+    for (const auto& vol : mVolumes) {
         vol->unmount();
     }
     return OK;

TrimTask.cpp

@@ -53,7 +53,7 @@ TrimTask::TrimTask(int flags) : mFlags(flags) {
     VolumeManager* vm = VolumeManager::Instance();
     std::list<std::string> privateIds;
     vm->listVolumes(VolumeBase::Type::kPrivate, privateIds);
-    for (auto id : privateIds) {
+    for (const auto& id : privateIds) {
         auto vol = vm->findVolume(id);
         if (vol != nullptr && vol->getState() == VolumeBase::State::kMounted) {
             mPaths.push_back(vol->getPath());
@@ -114,7 +114,7 @@ static void notifyResult(const std::string& path, int64_t bytes, int64_t delta)
 void TrimTask::run() {
     acquire_wake_lock(PARTIAL_WAKE_LOCK, kWakeLock);
 
-    for (auto path : mPaths) {
+    for (const auto& path : mPaths) {
         LOG(DEBUG) << "Starting trim of " << path;
 
         int fd = open(path.c_str(), O_RDONLY | O_DIRECTORY | O_CLOEXEC | O_NOFOLLOW);

Utils.cpp

@@ -208,7 +208,7 @@ static status_t readMetadata(const std::string& path, std::string& fsType,
     }
 
     char value[128];
-    for (auto line : output) {
+    for (const auto& line : output) {
         // Extract values from blkid output, if defined
         const char* cline = line.c_str();
         const char* start = strstr(cline, "TYPE=");

VolumeBase.cpp

@@ -219,7 +219,7 @@ status_t VolumeBase::unmount() {
     }
 
     setState(State::kEjecting);
-    for (auto vol : mVolumes) {
+    for (const auto& vol : mVolumes) {
         if (vol->destroy()) {
             LOG(WARNING) << getId() << " failed to destroy " << vol->getId()
                     << " stacked above";

VolumeManager.cpp

@@ -294,7 +294,7 @@ void VolumeManager::handleBlockEvent(NetlinkEvent *evt) {
 
     switch (evt->getAction()) {
     case NetlinkEvent::Action::kAdd: {
-        for (auto source : mDiskSources) {
+        for (const auto& source : mDiskSources) {
             if (source->matches(eventPath)) {
                 // For now, assume that MMC devices are SD, and that
                 // everything else is USB
@@ -316,7 +316,7 @@ void VolumeManager::handleBlockEvent(NetlinkEvent *evt) {
     }
     case NetlinkEvent::Action::kChange: {
         LOG(DEBUG) << "Disk at " << major << ":" << minor << " changed";
-        for (auto disk : mDisks) {
+        for (const auto& disk : mDisks) {
             if (disk->getDevice() == device) {
                 disk->readMetadata();
                 disk->readPartitions();
@@ -360,7 +360,7 @@ std::shared_ptr<android::vold::VolumeBase> VolumeManager::findVolume(const std::
     if (mInternalEmulated->getId() == id) {
         return mInternalEmulated;
     }
-    for (auto disk : mDisks) {
+    for (const auto& disk : mDisks) {
         auto vol = disk->findVolume(id);
         if (vol != nullptr) {
             return vol;
@@ -372,7 +372,7 @@ std::shared_ptr<android::vold::VolumeBase> VolumeManager::findVolume(const std::
 void VolumeManager::listVolumes(android::vold::VolumeBase::Type type,
         std::list<std::string>& list) {
     list.clear();
-    for (auto disk : mDisks) {
+    for (const auto& disk : mDisks) {
         disk->listVolumes(type, list);
     }
 }
@@ -503,7 +503,7 @@ static int unmount_tree(const char* path) {
     }
     endmntent(fp);
 
-    for (auto path : toUnmount) {
+    for (const auto& path : toUnmount) {
         if (umount2(path.c_str(), MNT_DETACH)) {
             ALOGW("Failed to unmount %s: %s", path.c_str(), strerror(errno));
         }
@@ -629,7 +629,7 @@ int VolumeManager::reset() {
     // newly connected framework hears all events.
     mInternalEmulated->destroy();
     mInternalEmulated->create();
-    for (auto disk : mDisks) {
+    for (const auto& disk : mDisks) {
         disk->destroy();
         disk->create();
     }
@@ -640,7 +640,7 @@ int VolumeManager::reset() {
 
 int VolumeManager::shutdown() {
     mInternalEmulated->destroy();
-    for (auto disk : mDisks) {
+    for (const auto& disk : mDisks) {
         disk->destroy();
     }
     mDisks.clear();
@@ -654,7 +654,7 @@ int VolumeManager::unmountAll() {
     if (mInternalEmulated != nullptr) {
         mInternalEmulated->unmount();
     }
-    for (auto disk : mDisks) {
+    for (const auto& disk : mDisks) {
         disk->unmountAll();
     }
 
@@ -678,7 +678,7 @@ int VolumeManager::unmountAll() {
     }
     endmntent(fp);
 
-    for (auto path : toUnmount) {
+    for (const auto& path : toUnmount) {
         SLOGW("Tearing down stale mount %s", path.c_str());
         android::vold::ForceUnmount(path);
     }