Conditionally use sdcardfs.

In preparation of sdcardfs going away on devices launching with R,
conditionally use it.

Bug: 146419093
Test: cuttlefish with sdcardfs, cuttlefish without sdcardfs but with
FUSE
Change-Id: I2c1d4b428dcb43c3fd274dde84d5088984161993

Utils.cpp

@@ -1017,9 +1017,6 @@ status_t MountUserFuse(userid_t user_id, const std::string& absolute_lower_path,
     std::string pass_through_path(
             StringPrintf("%s/%s", pre_pass_through_path.c_str(), relative_upper_path.c_str()));
 
-    std::string sdcardfs_path(
-            StringPrintf("/mnt/runtime/full/%s", relative_upper_path.c_str()));
-
     // Create directories.
     auto result = PrepareDir(pre_fuse_path, 0700, AID_ROOT, AID_ROOT);
     if (result != android::OK) {
@@ -1081,8 +1078,16 @@ status_t MountUserFuse(userid_t user_id, const std::string& absolute_lower_path,
         return -errno;
     }
 
+    if (IsFilesystemSupported("sdcardfs")) {
+        std::string sdcardfs_path(
+                StringPrintf("/mnt/runtime/full/%s", relative_upper_path.c_str()));
+
         LOG(INFO) << "Bind mounting " << sdcardfs_path << " to " << pass_through_path;
         return BindMount(sdcardfs_path, pass_through_path);
+    } else {
+        LOG(INFO) << "Bind mounting " << absolute_lower_path << " to " << pass_through_path;
+        return BindMount(absolute_lower_path, pass_through_path);
+    }
 }
 
 status_t UnmountUserFuse(userid_t user_id, const std::string& absolute_lower_path,

model/EmulatedVolume.cpp

@@ -48,6 +48,7 @@ EmulatedVolume::EmulatedVolume(const std::string& rawPath, int userId)
     mRawPath = rawPath;
     mLabel = "emulated";
     mFuseMounted = false;
+    mUseSdcardFs = IsFilesystemSupported("sdcardfs");
 }
 
 EmulatedVolume::EmulatedVolume(const std::string& rawPath, dev_t device, const std::string& fsUuid,
@@ -57,6 +58,7 @@ EmulatedVolume::EmulatedVolume(const std::string& rawPath, dev_t device, const s
     mRawPath = rawPath;
     mLabel = fsUuid;
     mFuseMounted = false;
+    mUseSdcardFs = IsFilesystemSupported("sdcardfs");
 }
 
 EmulatedVolume::~EmulatedVolume() {}
@@ -71,18 +73,23 @@ std::string EmulatedVolume::getLabel() {
     }
 }
 
-static status_t mountFuseBindMounts(int userId, const std::string& label) {
-    // TODO(b/134706060) we don't actually want to mount the "write" view by
-    // default, since it gives write access to all OBB dirs.
-    std::string androidSource(
-            StringPrintf("/mnt/runtime/default/%s/%d/Android", label.c_str(), userId));
+status_t EmulatedVolume::mountFuseBindMounts() {
+    std::string androidSource;
+    std::string label = getLabel();
+    int userId = getMountUserId();
+
+    if (mUseSdcardFs) {
+        androidSource = StringPrintf("/mnt/runtime/default/%s/%d/Android", label.c_str(), userId);
+    } else {
+        androidSource = StringPrintf("/%s/%d/Android", mRawPath.c_str(), userId);
+    }
     std::string androidTarget(
             StringPrintf("/mnt/user/%d/%s/%d/Android", userId, label.c_str(), userId));
 
     if (access(androidSource.c_str(), F_OK) != 0) {
         // Android path may not exist yet if users has just been created; create it on
         // the lower fs.
-        if (fs_prepare_dir(androidSource.c_str(), 0771, AID_ROOT, AID_ROOT) != 0) {
+        if (fs_prepare_dir(androidSource.c_str(), 0771, AID_MEDIA_RW, AID_MEDIA_RW) != 0) {
             PLOG(ERROR) << "Failed to create " << androidSource;
             return -errno;
         }
@@ -97,7 +104,10 @@ static status_t mountFuseBindMounts(int userId, const std::string& label) {
     return OK;
 }
 
-static status_t unmountFuseBindMounts(int userId, const std::string& label) {
+status_t EmulatedVolume::unmountFuseBindMounts() {
+    std::string label = getLabel();
+    int userId = getMountUserId();
+
     std::string androidTarget(
             StringPrintf("/mnt/user/%d/%s/%d/Android", userId, label.c_str(), userId));
 
@@ -137,7 +147,7 @@ status_t EmulatedVolume::doMount() {
 
     // Mount sdcardfs regardless of FUSE, since we need it to bind-mount on top of the
     // FUSE volume for various reasons.
-    if (getMountUserId() == 0) {
+    if (mUseSdcardFs && getMountUserId() == 0) {
         LOG(INFO) << "Executing sdcardfs";
         int sdcardFsPid;
         if (!(sdcardFsPid = fork())) {
@@ -203,7 +213,7 @@ status_t EmulatedVolume::doMount() {
         }
 
         // Only do the bind-mounts when we know for sure the FUSE daemon can resolve the path.
-        return mountFuseBindMounts(user_id, label);
+        return mountFuseBindMounts();
     }
 
     return OK;
@@ -231,7 +241,7 @@ status_t EmulatedVolume::doUnmount() {
         // Ignoring unmount return status because we do want to try to unmount
         // the rest cleanly.
 
-        unmountFuseBindMounts(userId, label);
+        unmountFuseBindMounts();
         if (UnmountUserFuse(userId, getInternalPath(), label) != OK) {
             PLOG(INFO) << "UnmountUserFuse failed on emulated fuse volume";
             return -errno;
@@ -239,7 +249,7 @@ status_t EmulatedVolume::doUnmount() {
 
         mFuseMounted = false;
     }
-    if (getMountUserId() != 0) {
+    if (getMountUserId() != 0 || !mUseSdcardFs) {
         // For sdcardfs, only unmount for user 0, since user 0 will always be running
         // and the paths don't change for different users.
         return OK;

model/EmulatedVolume.h

@@ -46,6 +46,9 @@ class EmulatedVolume : public VolumeBase {
     status_t doUnmount() override;
 
   private:
+    status_t mountFuseBindMounts();
+    status_t unmountFuseBindMounts();
+
     std::string getLabel();
     std::string mRawPath;
     std::string mLabel;
@@ -58,6 +61,9 @@ class EmulatedVolume : public VolumeBase {
     /* Whether we mounted FUSE for this volume */
     bool mFuseMounted;
 
+    /* Whether to use sdcardfs for this volume */
+    bool mUseSdcardFs;
+
     DISALLOW_COPY_AND_ASSIGN(EmulatedVolume);
 };
 

model/PublicVolume.cpp

@@ -51,6 +51,7 @@ PublicVolume::PublicVolume(dev_t device) : VolumeBase(Type::kPublic), mDevice(de
     setId(StringPrintf("public:%u,%u", major(device), minor(device)));
     mDevPath = StringPrintf("/dev/block/vold/%s", getId().c_str());
     mFuseMounted = false;
+    mUseSdcardFs = IsFilesystemSupported("sdcardfs");
 }
 
 PublicVolume::~PublicVolume() {}
@@ -161,6 +162,7 @@ status_t PublicVolume::doMount() {
         return OK;
     }
 
+    if (mUseSdcardFs) {
         if (fs_prepare_dir(mSdcardFsDefault.c_str(), 0700, AID_ROOT, AID_ROOT) ||
             fs_prepare_dir(mSdcardFsRead.c_str(), 0700, AID_ROOT, AID_ROOT) ||
             fs_prepare_dir(mSdcardFsWrite.c_str(), 0700, AID_ROOT, AID_ROOT) ||
@@ -222,6 +224,7 @@ status_t PublicVolume::doMount() {
         }
         /* sdcardfs will have exited already. The filesystem will still be running */
         TEMP_FAILURE_RETRY(waitpid(sdcardFsPid, nullptr, 0));
+    }
 
     bool isFuse = base::GetBoolProperty(kPropFuse, false);
     if (isFuse) {
@@ -275,22 +278,24 @@ status_t PublicVolume::doUnmount() {
 
     ForceUnmount(kAsecPath);
 
+    if (mUseSdcardFs) {
         ForceUnmount(mSdcardFsDefault);
         ForceUnmount(mSdcardFsRead);
         ForceUnmount(mSdcardFsWrite);
         ForceUnmount(mSdcardFsFull);
-    ForceUnmount(mRawPath);
 
         rmdir(mSdcardFsDefault.c_str());
         rmdir(mSdcardFsRead.c_str());
         rmdir(mSdcardFsWrite.c_str());
         rmdir(mSdcardFsFull.c_str());
-    rmdir(mRawPath.c_str());
 
         mSdcardFsDefault.clear();
         mSdcardFsRead.clear();
         mSdcardFsWrite.clear();
         mSdcardFsFull.clear();
+    }
+    ForceUnmount(mRawPath);
+    rmdir(mRawPath.c_str());
     mRawPath.clear();
 
     return OK;

model/PublicVolume.h

@@ -68,6 +68,9 @@ class PublicVolume : public VolumeBase {
     /* Whether we mounted FUSE for this volume */
     bool mFuseMounted;
 
+    /* Whether to use sdcardfs for this volume */
+    bool mUseSdcardFs;
+
     /* Filesystem type */
     std::string mFsType;
     /* Filesystem UUID */