diff --git a/Android.bp b/Android.bp
index 8d88e5f..e1877b9 100644
--- a/Android.bp
+++ b/Android.bp
@@ -28,6 +28,7 @@
     name: "vold_default_libs",
 
     static_libs: [
+        "libasync_safe",
         "libavb",
         "libbootloader_message",
         "libdm",
@@ -235,6 +236,7 @@
         "libhardware_legacy",
         "libhidlbase",
         "libkeymaster4support",
+        "libutils",
     ],
 }
 
@@ -271,6 +273,7 @@
     srcs: [
         "binder/android/os/IVold.aidl",
         "binder/android/os/IVoldListener.aidl",
+        "binder/android/os/IVoldMountCallback.aidl",
         "binder/android/os/IVoldTaskListener.aidl",
     ],
     path: "binder",
diff --git a/Keymaster.h b/Keymaster.h
index 42a2b5d..9a0616d 100644
--- a/Keymaster.h
+++ b/Keymaster.h
@@ -115,7 +115,7 @@
     bool isSecure();
 
   private:
-    std::unique_ptr<KmDevice> mDevice;
+    sp<KmDevice> mDevice;
     DISALLOW_COPY_AND_ASSIGN(Keymaster);
     static bool hmacKeyGenerated;
 };
diff --git a/Utils.cpp b/Utils.cpp
index 1616d80..af93824 100644
--- a/Utils.cpp
+++ b/Utils.cpp
@@ -165,7 +165,7 @@
     if (!umount2(cpath, UMOUNT_NOFOLLOW) || errno == EINVAL || errno == ENOENT) {
         return OK;
     }
-
+    PLOG(INFO) << "ForceUnmount failed";
     return -errno;
 }
 
@@ -985,5 +985,107 @@
     return true;
 }
 
+status_t MountUserFuse(userid_t user_id, const std::string& absolute_lower_path,
+                       const std::string& relative_upper_path, android::base::unique_fd* fuse_fd) {
+    std::string pre_fuse_path(StringPrintf("/mnt/user/%d", user_id));
+    std::string fuse_path(
+            StringPrintf("%s/%s", pre_fuse_path.c_str(), relative_upper_path.c_str()));
+
+    std::string pre_pass_through_path(StringPrintf("/mnt/pass_through/%d", user_id));
+    std::string pass_through_path(
+            StringPrintf("%s/%s", pre_pass_through_path.c_str(), relative_upper_path.c_str()));
+
+    // Force remove the existing mount before we attempt to prepare the
+    // directory. If we have a dangling mount, then PrepareDir may fail if the
+    // indirection to FUSE doesn't work.
+    android::status_t result = UnmountUserFuse(pass_through_path, fuse_path);
+    if (result != android::OK) {
+        return -1;
+    }
+
+    // Create directories.
+    result = PrepareDir(pre_fuse_path, 0700, AID_ROOT, AID_ROOT);
+    if (result != android::OK) {
+        PLOG(ERROR) << "Failed to prepare directory " << pre_fuse_path;
+        return -1;
+    }
+
+    result = PrepareDir(fuse_path, 0700, AID_ROOT, AID_ROOT);
+    if (result != android::OK) {
+        PLOG(ERROR) << "Failed to prepare directory " << fuse_path;
+        return -1;
+    }
+
+    result = PrepareDir(pre_pass_through_path, 0755, AID_ROOT, AID_ROOT);
+    if (result != android::OK) {
+        PLOG(ERROR) << "Failed to prepare directory " << pre_pass_through_path;
+        return -1;
+    }
+
+    result = PrepareDir(pass_through_path, 0755, AID_ROOT, AID_ROOT);
+    if (result != android::OK) {
+        PLOG(ERROR) << "Failed to prepare directory " << pass_through_path;
+        return -1;
+    }
+
+    if (relative_upper_path == "emulated") {
+        std::string linkpath(StringPrintf("/mnt/user/%d/self", user_id));
+        result = PrepareDir(linkpath, 0755, AID_ROOT, AID_ROOT);
+        if (result != android::OK) {
+            PLOG(ERROR) << "Failed to prepare directory " << linkpath;
+            return -1;
+        }
+        linkpath += "/primary";
+
+        Symlink(fuse_path + "/" + std::to_string(user_id), linkpath);
+    }
+
+    // Open fuse fd.
+    fuse_fd->reset(open("/dev/fuse", O_RDWR | O_CLOEXEC));
+    if (fuse_fd->get() == -1) {
+        PLOG(ERROR) << "Failed to open /dev/fuse";
+        return -1;
+    }
+
+    // Note: leaving out default_permissions since we don't want kernel to do lower filesystem
+    // permission checks before routing to FUSE daemon.
+    const auto opts = StringPrintf(
+        "fd=%i,"
+        "rootmode=40000,"
+        "allow_other,"
+        "user_id=0,group_id=0,",
+        fuse_fd->get());
+
+    result = TEMP_FAILURE_RETRY(mount("/dev/fuse", fuse_path.c_str(), "fuse",
+                                      MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_NOATIME | MS_LAZYTIME,
+                                      opts.c_str()));
+    if (result != 0) {
+        PLOG(ERROR) << "Failed to mount " << fuse_path;
+        return -errno;
+    }
+    LOG(INFO) << "Bind mounting to " << absolute_lower_path;
+    return BindMount(absolute_lower_path, pass_through_path);
+}
+
+status_t UnmountUserFuse(const std::string& pass_through_path, const std::string& fuse_path) {
+    // Best effort unmount pass_through path
+    sSleepOnUnmount = false;
+    ForceUnmount(pass_through_path);
+    android::status_t result = ForceUnmount(fuse_path);
+    sSleepOnUnmount = true;
+    if (result != android::OK) {
+        // TODO(b/135341433): MNT_DETACH is needed for fuse because umount2 can fail with EBUSY.
+        // Figure out why we get EBUSY and remove this special casing if possible.
+        PLOG(ERROR) << "Failed to unmount. Trying MNT_DETACH " << fuse_path << " ...";
+        if (umount2(fuse_path.c_str(), UMOUNT_NOFOLLOW | MNT_DETACH) && errno != EINVAL &&
+            errno != ENOENT) {
+            PLOG(ERROR) << "Failed to unmount with MNT_DETACH " << fuse_path;
+            return -errno;
+        }
+        return android::OK;
+    }
+    return result;
+}
+
 }  // namespace vold
 }  // namespace android
diff --git a/Utils.h b/Utils.h
index af4e401..375e175 100644
--- a/Utils.h
+++ b/Utils.h
@@ -20,6 +20,7 @@
 #include "KeyBuffer.h"
 
 #include <android-base/macros.h>
+#include <android-base/unique_fd.h>
 #include <cutils/multiuser.h>
 #include <selinux/selinux.h>
 #include <utils/Errors.h>
@@ -33,6 +34,8 @@
 namespace android {
 namespace vold {
 
+static const char* kPropFuseSnapshot = "sys.fuse_snapshot";
+
 /* SELinux contexts used depending on the block device type */
 extern security_context_t sBlkidContext;
 extern security_context_t sBlkidUntrustedContext;
@@ -147,6 +150,12 @@
 bool FsyncDirectory(const std::string& dirname);
 
 bool writeStringToFile(const std::string& payload, const std::string& filename);
+
+status_t MountUserFuse(userid_t user_id, const std::string& absolute_lower_path,
+                       const std::string& relative_upper_path, android::base::unique_fd* fuse_fd);
+
+status_t UnmountUserFuse(const std::string& pass_through_path, const std::string& fuse_path);
+
 }  // namespace vold
 }  // namespace android
 
diff --git a/VoldNativeService.cpp b/VoldNativeService.cpp
index cc32820..b82ea06 100644
--- a/VoldNativeService.cpp
+++ b/VoldNativeService.cpp
@@ -108,7 +108,7 @@
         return exception(binder::Status::EX_ILLEGAL_ARGUMENT, "Missing ID");
     }
     for (const char& c : id) {
-        if (!std::isalnum(c) && c != ':' && c != ',') {
+        if (!std::isalnum(c) && c != ':' && c != ',' && c != ';') {
             return exception(binder::Status::EX_ILLEGAL_ARGUMENT,
                              StringPrintf("ID %s is malformed", id.c_str()));
         }
@@ -326,8 +326,9 @@
     return translate(VolumeManager::Instance()->forgetPartition(partGuid, fsUuid));
 }
 
-binder::Status VoldNativeService::mount(const std::string& volId, int32_t mountFlags,
-                                        int32_t mountUserId) {
+binder::Status VoldNativeService::mount(
+        const std::string& volId, int32_t mountFlags, int32_t mountUserId,
+        const android::sp<android::os::IVoldMountCallback>& callback) {
     ENFORCE_SYSTEM_OR_ROOT;
     CHECK_ARGUMENT_ID(volId);
     ACQUIRE_LOCK;
@@ -340,10 +341,14 @@
     vol->setMountFlags(mountFlags);
     vol->setMountUserId(mountUserId);
 
+    vol->setMountCallback(callback);
     int res = vol->mount();
+    vol->setMountCallback(nullptr);
+
     if (res != OK) {
         return translate(res);
     }
+
     if ((mountFlags & MOUNT_FLAG_PRIMARY) != 0) {
         res = VolumeManager::Instance()->setPrimary(vol);
         if (res != OK) {
diff --git a/VoldNativeService.h b/VoldNativeService.h
index 0718263..ebd9041 100644
--- a/VoldNativeService.h
+++ b/VoldNativeService.h
@@ -52,7 +52,8 @@
     binder::Status partition(const std::string& diskId, int32_t partitionType, int32_t ratio);
     binder::Status forgetPartition(const std::string& partGuid, const std::string& fsUuid);
 
-    binder::Status mount(const std::string& volId, int32_t mountFlags, int32_t mountUserId);
+    binder::Status mount(const std::string& volId, int32_t mountFlags, int32_t mountUserId,
+                         const android::sp<android::os::IVoldMountCallback>& callback);
     binder::Status unmount(const std::string& volId);
     binder::Status format(const std::string& volId, const std::string& fsType);
     binder::Status benchmark(const std::string& volId,
diff --git a/VolumeManager.cpp b/VolumeManager.cpp
index 44bff5a..f1cd232 100644
--- a/VolumeManager.cpp
+++ b/VolumeManager.cpp
@@ -40,6 +40,7 @@
 #include <android-base/properties.h>
 #include <android-base/stringprintf.h>
 #include <android-base/strings.h>
+#include <async_safe/log.h>
 
 #include <cutils/fs.h>
 #include <utils/Trace.h>
@@ -67,6 +68,7 @@
 #include "fs/Vfat.h"
 #include "model/EmulatedVolume.h"
 #include "model/ObbVolume.h"
+#include "model/PrivateVolume.h"
 #include "model/StubVolume.h"
 
 using android::OK;
@@ -79,10 +81,12 @@
 using android::vold::CreateDir;
 using android::vold::DeleteDirContents;
 using android::vold::DeleteDirContentsAndDir;
+using android::vold::PrivateVolume;
 using android::vold::Symlink;
 using android::vold::Unlink;
 using android::vold::UnmountTree;
 using android::vold::VoldNativeService;
+using android::vold::VolumeBase;
 
 static const char* kPathUserMount = "/mnt/user";
 static const char* kPathVirtualDisk = "/data/misc/vold/virtual_disk";
@@ -174,10 +178,13 @@
 
     // Assume that we always have an emulated volume on internal
     // storage; the framework will decide if it should be mounted.
-    CHECK(mInternalEmulated == nullptr);
-    mInternalEmulated = std::shared_ptr<android::vold::VolumeBase>(
-        new android::vold::EmulatedVolume("/data/media"));
-    mInternalEmulated->create();
+    CHECK(mInternalEmulatedVolumes.empty());
+
+    auto vol = std::shared_ptr<android::vold::VolumeBase>(
+            new android::vold::EmulatedVolume("/data/media", 0));
+    vol->setMountUserId(0);
+    vol->create();
+    mInternalEmulatedVolumes.push_back(vol);
 
     // Consider creating a virtual disk
     updateVirtualDisk();
@@ -186,9 +193,12 @@
 }
 
 int VolumeManager::stop() {
-    CHECK(mInternalEmulated != nullptr);
-    mInternalEmulated->destroy();
-    mInternalEmulated = nullptr;
+    CHECK(!mInternalEmulatedVolumes.empty());
+    for (const auto& vol : mInternalEmulatedVolumes) {
+        vol->destroy();
+    }
+    mInternalEmulatedVolumes.clear();
+
     return 0;
 }
 
@@ -310,11 +320,10 @@
 }
 
 std::shared_ptr<android::vold::VolumeBase> VolumeManager::findVolume(const std::string& id) {
-    // Vold could receive "mount" after "shutdown" command in the extreme case.
-    // If this happens, mInternalEmulated will equal nullptr and
-    // we need to deal with it in order to avoid null pointer crash.
-    if (mInternalEmulated != nullptr && mInternalEmulated->getId() == id) {
-        return mInternalEmulated;
+    for (const auto& vol : mInternalEmulatedVolumes) {
+        if (vol->getId() == id) {
+            return vol;
+        }
     }
     for (const auto& disk : mDisks) {
         auto vol = disk->findVolume(id);
@@ -365,45 +374,123 @@
 }
 
 int VolumeManager::linkPrimary(userid_t userId) {
-    std::string source(mPrimary->getPath());
-    if (mPrimary->isEmulated()) {
-        source = StringPrintf("%s/%d", source.c_str(), userId);
-        fs_prepare_dir(source.c_str(), 0755, AID_ROOT, AID_ROOT);
-    }
+    if (!GetBoolProperty(android::vold::kPropFuseSnapshot, false)) {
+        std::string source(mPrimary->getPath());
+        if (mPrimary->isEmulated()) {
+            source = StringPrintf("%s/%d", source.c_str(), userId);
+            fs_prepare_dir(source.c_str(), 0755, AID_ROOT, AID_ROOT);
+        }
 
-    std::string target(StringPrintf("/mnt/user/%d/primary", userId));
-    LOG(DEBUG) << "Linking " << source << " to " << target;
-    Symlink(source, target);
+        std::string target(StringPrintf("/mnt/user/%d/primary", userId));
+        LOG(DEBUG) << "Linking " << source << " to " << target;
+        Symlink(source, target);
+    }
     return 0;
 }
 
+void VolumeManager::destroyEmulatedVolumesForUser(userid_t userId) {
+    // Destroy and remove all unstacked EmulatedVolumes for the user
+    auto i = mInternalEmulatedVolumes.begin();
+    while (i != mInternalEmulatedVolumes.end()) {
+        auto vol = *i;
+        if (vol->getMountUserId() == userId) {
+            vol->destroy();
+            i = mInternalEmulatedVolumes.erase(i);
+        } else {
+            i++;
+        }
+    }
+
+    // Destroy and remove all stacked EmulatedVolumes for the user on each mounted private volume
+    std::list<std::string> private_vols;
+    listVolumes(VolumeBase::Type::kPrivate, private_vols);
+    for (const std::string& id : private_vols) {
+        PrivateVolume* pvol = static_cast<PrivateVolume*>(findVolume(id).get());
+        std::list<std::shared_ptr<VolumeBase>> vols_to_remove;
+        if (pvol->getState() == VolumeBase::State::kMounted) {
+            for (const auto& vol : pvol->getVolumes()) {
+                if (vol->getMountUserId() == userId) {
+                    vols_to_remove.push_back(vol);
+                }
+            }
+            for (const auto& vol : vols_to_remove) {
+                vol->destroy();
+                pvol->removeVolume(vol);
+            }
+        }  // else EmulatedVolumes will be destroyed on VolumeBase#unmount
+    }
+}
+
+void VolumeManager::createEmulatedVolumesForUser(userid_t userId) {
+    // Create unstacked EmulatedVolumes for the user
+    auto vol = std::shared_ptr<android::vold::VolumeBase>(
+            new android::vold::EmulatedVolume("/data/media", userId));
+    vol->setMountUserId(userId);
+    mInternalEmulatedVolumes.push_back(vol);
+    vol->create();
+
+    // Create stacked EmulatedVolumes for the user on each PrivateVolume
+    std::list<std::string> private_vols;
+    listVolumes(VolumeBase::Type::kPrivate, private_vols);
+    for (const std::string& id : private_vols) {
+        PrivateVolume* pvol = static_cast<PrivateVolume*>(findVolume(id).get());
+        if (pvol->getState() == VolumeBase::State::kMounted) {
+            auto evol =
+                    std::shared_ptr<android::vold::VolumeBase>(new android::vold::EmulatedVolume(
+                            pvol->getPath() + "/media", pvol->getRawDevice(), pvol->getFsUuid(),
+                            userId));
+            evol->setMountUserId(userId);
+            pvol->addVolume(evol);
+            evol->create();
+        }  // else EmulatedVolumes will be created per user when on PrivateVolume#doMount
+    }
+}
+
 int VolumeManager::onUserAdded(userid_t userId, int userSerialNumber) {
+    LOG(INFO) << "onUserAdded: " << userId;
+
     mAddedUsers[userId] = userSerialNumber;
     return 0;
 }
 
 int VolumeManager::onUserRemoved(userid_t userId) {
+    LOG(INFO) << "onUserRemoved: " << userId;
+
+    onUserStopped(userId);
     mAddedUsers.erase(userId);
     return 0;
 }
 
 int VolumeManager::onUserStarted(userid_t userId) {
-    LOG(VERBOSE) << "onUserStarted: " << userId;
-    // Note that sometimes the system will spin up processes from Zygote
-    // before actually starting the user, so we're okay if Zygote
-    // already created this directory.
-    std::string path(StringPrintf("%s/%d", kPathUserMount, userId));
-    fs_prepare_dir(path.c_str(), 0755, AID_ROOT, AID_ROOT);
+    LOG(INFO) << "onUserStarted: " << userId;
+
+    if (mStartedUsers.find(userId) == mStartedUsers.end()) {
+        createEmulatedVolumesForUser(userId);
+    }
+
+    if (!GetBoolProperty(android::vold::kPropFuseSnapshot, false)) {
+        // Note that sometimes the system will spin up processes from Zygote
+        // before actually starting the user, so we're okay if Zygote
+        // already created this directory.
+        std::string path(StringPrintf("%s/%d", kPathUserMount, userId));
+        fs_prepare_dir(path.c_str(), 0755, AID_ROOT, AID_ROOT);
+
+        if (mPrimary) {
+            linkPrimary(userId);
+        }
+    }
 
     mStartedUsers.insert(userId);
-    if (mPrimary) {
-        linkPrimary(userId);
-    }
     return 0;
 }
 
 int VolumeManager::onUserStopped(userid_t userId) {
     LOG(VERBOSE) << "onUserStopped: " << userId;
+
+    if (mStartedUsers.find(userId) != mStartedUsers.end()) {
+        destroyEmulatedVolumesForUser(userId);
+    }
+
     mStartedUsers.erase(userId);
     return 0;
 }
@@ -430,7 +517,56 @@
     return 0;
 }
 
+// This code is executed after a fork so it's very important that the set of
+// methods we call here is strictly limited.
+//
+// TODO: Get rid of this guesswork altogether and instead exec a process
+// immediately after fork to do our bindding for us.
+static bool childProcess(const char* storageSource, const char* userSource, int nsFd,
+                         struct dirent* de) {
+    if (setns(nsFd, CLONE_NEWNS) != 0) {
+        async_safe_format_log(ANDROID_LOG_ERROR, "vold", "Failed to setns for %s :%s", de->d_name,
+                              strerror(errno));
+        return false;
+    }
+
+    // NOTE: Inlined from vold::UnmountTree here to avoid using PLOG methods and
+    // to also protect against future changes that may cause issues across a
+    // fork.
+    if (TEMP_FAILURE_RETRY(umount2("/storage/", MNT_DETACH)) < 0 && errno != EINVAL &&
+        errno != ENOENT) {
+        async_safe_format_log(ANDROID_LOG_ERROR, "vold", "Failed to unmount /storage/ :%s",
+                              strerror(errno));
+        return false;
+    }
+
+    if (TEMP_FAILURE_RETRY(mount(storageSource, "/storage", NULL, MS_BIND | MS_REC, NULL)) == -1) {
+        async_safe_format_log(ANDROID_LOG_ERROR, "vold", "Failed to mount %s for %s :%s",
+                              storageSource, de->d_name, strerror(errno));
+        return false;
+    }
+
+    if (TEMP_FAILURE_RETRY(mount(NULL, "/storage", NULL, MS_REC | MS_SLAVE, NULL)) == -1) {
+        async_safe_format_log(ANDROID_LOG_ERROR, "vold",
+                              "Failed to set MS_SLAVE to /storage for %s :%s", de->d_name,
+                              strerror(errno));
+        return false;
+    }
+
+    if (TEMP_FAILURE_RETRY(mount(userSource, "/storage/self", NULL, MS_BIND, NULL)) == -1) {
+        async_safe_format_log(ANDROID_LOG_ERROR, "vold", "Failed to mount %s for %s :%s",
+                              userSource, de->d_name, strerror(errno));
+        return false;
+    }
+
+    return true;
+}
+
 int VolumeManager::remountUid(uid_t uid, int32_t mountMode) {
+    if (GetBoolProperty(android::vold::kPropFuseSnapshot, false)) {
+        // TODO(135341433): Implement fuse specific logic.
+        return 0;
+    }
     std::string mode;
     switch (mountMode) {
         case VoldNativeService::REMOUNT_MODE_NONE:
@@ -450,6 +586,9 @@
         case VoldNativeService::REMOUNT_MODE_FULL:
             mode = "full";
             break;
+        case VoldNativeService::REMOUNT_MODE_PASS_THROUGH:
+            mode = "pass_through";
+            break;
         default:
             PLOG(ERROR) << "Unknown mode " << std::to_string(mountMode);
             return -1;
@@ -464,6 +603,8 @@
     int nsFd;
     struct stat sb;
     pid_t child;
+    std::string userSource;
+    std::string storageSource;
 
     static bool apexUpdatable = android::sysprop::ApexProperties::updatable().value_or(false);
 
@@ -539,47 +680,28 @@
             goto next;
         }
 
+        if (mode == "default") {
+            storageSource = "/mnt/runtime/default";
+        } else if (mode == "read") {
+            storageSource = "/mnt/runtime/read";
+        } else if (mode == "write") {
+            storageSource = "/mnt/runtime/write";
+        } else if (mode == "full") {
+            storageSource = "/mnt/runtime/full";
+        } else {
+            // Sane default of no storage visible. No need to fork a child
+            // to remount uid.
+            goto next;
+        }
+
+        // Mount user-specific symlink helper into place
+        userSource = StringPrintf("/mnt/user/%d", multiuser_get_user_id(uid));
         if (!(child = fork())) {
-            if (setns(nsFd, CLONE_NEWNS) != 0) {
-                PLOG(ERROR) << "Failed to setns for " << de->d_name;
-                _exit(1);
-            }
-
-            android::vold::UnmountTree("/storage/");
-
-            std::string storageSource;
-            if (mode == "default") {
-                storageSource = "/mnt/runtime/default";
-            } else if (mode == "read") {
-                storageSource = "/mnt/runtime/read";
-            } else if (mode == "write") {
-                storageSource = "/mnt/runtime/write";
-            } else if (mode == "full") {
-                storageSource = "/mnt/runtime/full";
-            } else {
-                // Sane default of no storage visible
+            if (childProcess(storageSource.c_str(), userSource.c_str(), nsFd, de)) {
                 _exit(0);
-            }
-            if (TEMP_FAILURE_RETRY(
-                    mount(storageSource.c_str(), "/storage", NULL, MS_BIND | MS_REC, NULL)) == -1) {
-                PLOG(ERROR) << "Failed to mount " << storageSource << " for " << de->d_name;
+            } else {
                 _exit(1);
             }
-            if (TEMP_FAILURE_RETRY(mount(NULL, "/storage", NULL, MS_REC | MS_SLAVE, NULL)) == -1) {
-                PLOG(ERROR) << "Failed to set MS_SLAVE to /storage for " << de->d_name;
-                _exit(1);
-            }
-
-            // Mount user-specific symlink helper into place
-            userid_t user_id = multiuser_get_user_id(uid);
-            std::string userSource(StringPrintf("/mnt/user/%d", user_id));
-            if (TEMP_FAILURE_RETRY(
-                    mount(userSource.c_str(), "/storage/self", NULL, MS_BIND, NULL)) == -1) {
-                PLOG(ERROR) << "Failed to mount " << userSource << " for " << de->d_name;
-                _exit(1);
-            }
-
-            _exit(0);
         }
 
         if (child == -1) {
@@ -600,10 +722,11 @@
 int VolumeManager::reset() {
     // Tear down all existing disks/volumes and start from a blank slate so
     // newly connected framework hears all events.
-    if (mInternalEmulated != nullptr) {
-        mInternalEmulated->destroy();
-        mInternalEmulated->create();
+    for (const auto& vol : mInternalEmulatedVolumes) {
+        vol->destroy();
     }
+    mInternalEmulatedVolumes.clear();
+
     for (const auto& disk : mDisks) {
         disk->destroy();
         disk->create();
@@ -616,15 +739,18 @@
 
 // Can be called twice (sequentially) during shutdown. should be safe for that.
 int VolumeManager::shutdown() {
-    if (mInternalEmulated == nullptr) {
+    if (mInternalEmulatedVolumes.empty()) {
         return 0;  // already shutdown
     }
     android::vold::sSleepOnUnmount = false;
-    mInternalEmulated->destroy();
-    mInternalEmulated = nullptr;
+    for (const auto& vol : mInternalEmulatedVolumes) {
+        vol->destroy();
+    }
     for (const auto& disk : mDisks) {
         disk->destroy();
     }
+
+    mInternalEmulatedVolumes.clear();
     mStubVolumes.clear();
     mDisks.clear();
     mPendingDisks.clear();
@@ -637,8 +763,8 @@
     ATRACE_NAME("VolumeManager::unmountAll()");
 
     // First, try gracefully unmounting all known devices
-    if (mInternalEmulated != nullptr) {
-        mInternalEmulated->unmount();
+    for (const auto& vol : mInternalEmulatedVolumes) {
+        vol->unmount();
     }
     for (const auto& stub : mStubVolumes) {
         stub->unmount();
diff --git a/VolumeManager.h b/VolumeManager.h
index 9bf7599..aff5aaf 100644
--- a/VolumeManager.h
+++ b/VolumeManager.h
@@ -84,6 +84,8 @@
 
     void listVolumes(android::vold::VolumeBase::Type type, std::list<std::string>& list) const;
 
+    const std::unordered_set<userid_t>& getStartedUsers() const { return mStartedUsers; }
+
     int forgetPartition(const std::string& partGuid, const std::string& fsUuid);
 
     int onUserAdded(userid_t userId, int userSerialNumber);
@@ -137,6 +139,9 @@
 
     int linkPrimary(userid_t userId);
 
+    void createEmulatedVolumesForUser(userid_t userId);
+    void destroyEmulatedVolumesForUser(userid_t userId);
+
     void handleDiskAdded(const std::shared_ptr<android::vold::Disk>& disk);
     void handleDiskChanged(dev_t device);
     void handleDiskRemoved(dev_t device);
@@ -151,13 +156,13 @@
     std::list<std::shared_ptr<android::vold::Disk>> mPendingDisks;
     std::list<std::shared_ptr<android::vold::VolumeBase>> mObbVolumes;
     std::list<std::shared_ptr<android::vold::VolumeBase>> mStubVolumes;
+    std::list<std::shared_ptr<android::vold::VolumeBase>> mInternalEmulatedVolumes;
 
     std::unordered_map<userid_t, int> mAddedUsers;
     std::unordered_set<userid_t> mStartedUsers;
 
     std::string mVirtualDiskPath;
     std::shared_ptr<android::vold::Disk> mVirtualDisk;
-    std::shared_ptr<android::vold::VolumeBase> mInternalEmulated;
     std::shared_ptr<android::vold::VolumeBase> mPrimary;
 
     int mNextObbId;
diff --git a/binder/android/os/IVold.aidl b/binder/android/os/IVold.aidl
index 681e9dc..975d94c 100644
--- a/binder/android/os/IVold.aidl
+++ b/binder/android/os/IVold.aidl
@@ -18,6 +18,7 @@
 
 import android.os.incremental.IncrementalFileSystemControlParcel;
 import android.os.IVoldListener;
+import android.os.IVoldMountCallback;
 import android.os.IVoldTaskListener;
 
 /** {@hide} */
@@ -41,7 +42,8 @@
     void partition(@utf8InCpp String diskId, int partitionType, int ratio);
     void forgetPartition(@utf8InCpp String partGuid, @utf8InCpp String fsUuid);
 
-    void mount(@utf8InCpp String volId, int mountFlags, int mountUserId);
+    void mount(@utf8InCpp String volId, int mountFlags, int mountUserId,
+         @nullable IVoldMountCallback callback);
     void unmount(@utf8InCpp String volId);
     void format(@utf8InCpp String volId, @utf8InCpp String fsType);
     void benchmark(@utf8InCpp String volId, IVoldTaskListener listener);
@@ -164,6 +166,7 @@
     const int REMOUNT_MODE_LEGACY = 4;
     const int REMOUNT_MODE_INSTALLER = 5;
     const int REMOUNT_MODE_FULL = 6;
+    const int REMOUNT_MODE_PASS_THROUGH = 7;
 
     const int VOLUME_STATE_UNMOUNTED = 0;
     const int VOLUME_STATE_CHECKING = 1;
diff --git a/binder/android/os/IVoldListener.aidl b/binder/android/os/IVoldListener.aidl
index 0dcfc04..b3e4ba5 100644
--- a/binder/android/os/IVoldListener.aidl
+++ b/binder/android/os/IVoldListener.aidl
@@ -25,7 +25,7 @@
     void onDiskDestroyed(@utf8InCpp String diskId);
 
     void onVolumeCreated(@utf8InCpp String volId,
-            int type, @utf8InCpp String diskId, @utf8InCpp String partGuid);
+            int type, @utf8InCpp String diskId, @utf8InCpp String partGuid, int userId);
     void onVolumeStateChanged(@utf8InCpp String volId, int state);
     void onVolumeMetadataChanged(@utf8InCpp String volId,
             @utf8InCpp String fsType, @utf8InCpp String fsUuid, @utf8InCpp String fsLabel);
diff --git a/binder/android/os/IVoldMountCallback.aidl b/binder/android/os/IVoldMountCallback.aidl
new file mode 100644
index 0000000..6bf46d7
--- /dev/null
+++ b/binder/android/os/IVoldMountCallback.aidl
@@ -0,0 +1,23 @@
+/*
+ * Copyright (C) 2019 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.
+ */
+
+package android.os;
+
+/** {@hide} */
+interface IVoldMountCallback {
+    boolean onVolumeChecking(FileDescriptor fuseFd, @utf8InCpp String path,
+        @utf8InCpp String internalPath);
+}
diff --git a/model/EmulatedVolume.cpp b/model/EmulatedVolume.cpp
index 552fe2f..eb6b8a3 100644
--- a/model/EmulatedVolume.cpp
+++ b/model/EmulatedVolume.cpp
@@ -15,10 +15,13 @@
  */
 
 #include "EmulatedVolume.h"
+
+#include "AppFuseUtil.h"
 #include "Utils.h"
 #include "VolumeManager.h"
 
 #include <android-base/logging.h>
+#include <android-base/properties.h>
 #include <android-base/stringprintf.h>
 #include <cutils/fs.h>
 #include <private/android_filesystem_config.h>
@@ -39,16 +42,17 @@
 
 static const char* kFusePath = "/system/bin/sdcard";
 
-EmulatedVolume::EmulatedVolume(const std::string& rawPath)
+EmulatedVolume::EmulatedVolume(const std::string& rawPath, int userId)
     : VolumeBase(Type::kEmulated), mFusePid(0) {
-    setId("emulated");
+    setId(StringPrintf("emulated;%u", userId));
     mRawPath = rawPath;
     mLabel = "emulated";
 }
 
-EmulatedVolume::EmulatedVolume(const std::string& rawPath, dev_t device, const std::string& fsUuid)
+EmulatedVolume::EmulatedVolume(const std::string& rawPath, dev_t device, const std::string& fsUuid,
+                               int userId)
     : VolumeBase(Type::kEmulated), mFusePid(0) {
-    setId(StringPrintf("emulated:%u,%u", major(device), minor(device)));
+    setId(StringPrintf("emulated:%u,%u;%u", major(device), minor(device), userId));
     mRawPath = rawPath;
     mLabel = fsUuid;
 }
@@ -81,6 +85,37 @@
 
     dev_t before = GetDevice(mFuseFull);
 
+    bool isFuse = base::GetBoolProperty(kPropFuseSnapshot, false);
+
+    if (isFuse) {
+        LOG(INFO) << "Mounting emulated fuse volume";
+        android::base::unique_fd fd;
+        int user_id = getMountUserId();
+        int result = MountUserFuse(user_id, getInternalPath(), label, &fd);
+
+        if (result != 0) {
+            PLOG(ERROR) << "Failed to mount emulated fuse volume";
+            return -result;
+        }
+
+        auto callback = getMountCallback();
+        if (callback) {
+            bool is_ready = false;
+            callback->onVolumeChecking(std::move(fd), getPath(), getInternalPath(), &is_ready);
+            if (!is_ready) {
+                return -EIO;
+            }
+        }
+
+        return OK;
+    } else if (getMountUserId() != 0) {
+        // For sdcardfs, only mount for user 0, since user 0 will always be running
+        // and the paths don't change for different users. Trying to double mount
+        // will cause sepolicy to scream since sdcardfs prevents 'mounton'
+        return OK;
+    }
+
+    LOG(INFO) << "Executing sdcardfs";
     if (!(mFusePid = fork())) {
         // clang-format off
         if (execl(kFusePath, kFusePath,
@@ -131,6 +166,33 @@
     // ENOTCONN until the unmount completes. This is an exotic and unusual
     // error code and might cause broken behaviour in applications.
     KillProcessesUsingPath(getPath());
+
+    bool isFuse = base::GetBoolProperty(kPropFuseSnapshot, false);
+    if (isFuse) {
+        // We could have migrated storage to an adopted private volume, so always
+        // call primary storage "emulated" to avoid media rescans.
+        std::string label = mLabel;
+        if (getMountFlags() & MountFlags::kPrimary) {
+            label = "emulated";
+        }
+
+        std::string fuse_path(StringPrintf("/mnt/user/%d/%s", getMountUserId(), label.c_str()));
+        std::string pass_through_path(
+                StringPrintf("/mnt/pass_through/%d/%s", getMountUserId(), label.c_str()));
+        if (UnmountUserFuse(pass_through_path, fuse_path) != OK) {
+            PLOG(INFO) << "UnmountUserFuse failed on emulated fuse volume";
+            return -errno;
+        }
+
+        rmdir(fuse_path.c_str());
+        rmdir(pass_through_path.c_str());
+        return OK;
+    } else if (getMountUserId() != 0) {
+        // 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;
+    }
+
     ForceUnmount(mFuseDefault);
     ForceUnmount(mFuseRead);
     ForceUnmount(mFuseWrite);
diff --git a/model/EmulatedVolume.h b/model/EmulatedVolume.h
index fddfe4e..8d4c490 100644
--- a/model/EmulatedVolume.h
+++ b/model/EmulatedVolume.h
@@ -37,8 +37,8 @@
  */
 class EmulatedVolume : public VolumeBase {
   public:
-    explicit EmulatedVolume(const std::string& rawPath);
-    EmulatedVolume(const std::string& rawPath, dev_t device, const std::string& fsUuid);
+    explicit EmulatedVolume(const std::string& rawPath, int userId);
+    EmulatedVolume(const std::string& rawPath, dev_t device, const std::string& fsUuid, int userId);
     virtual ~EmulatedVolume();
 
   protected:
diff --git a/model/PrivateVolume.cpp b/model/PrivateVolume.cpp
index de2a09f..5098e5d 100644
--- a/model/PrivateVolume.cpp
+++ b/model/PrivateVolume.cpp
@@ -155,12 +155,18 @@
         return -EIO;
     }
 
-    // Create a new emulated volume stacked above us, it will automatically
-    // be destroyed during unmount
+    auto vol_manager = VolumeManager::Instance();
     std::string mediaPath(mPath + "/media");
-    auto vol = std::shared_ptr<VolumeBase>(new EmulatedVolume(mediaPath, mRawDevice, mFsUuid));
-    addVolume(vol);
-    vol->create();
+
+    // Create a new emulated volume stacked above us for all added users, they will automatically
+    // be destroyed during unmount
+    for (userid_t user : vol_manager->getStartedUsers()) {
+        auto vol = std::shared_ptr<VolumeBase>(
+                new EmulatedVolume(mediaPath, mRawDevice, mFsUuid, user));
+        vol->setMountUserId(user);
+        addVolume(vol);
+        vol->create();
+    }
 
     return OK;
 }
diff --git a/model/PrivateVolume.h b/model/PrivateVolume.h
index cb8e75d..656172f 100644
--- a/model/PrivateVolume.h
+++ b/model/PrivateVolume.h
@@ -42,6 +42,8 @@
     const std::string& getFsType() const { return mFsType; };
     const std::string& getRawDevPath() const { return mRawDevPath; };
     const std::string& getRawDmDevPath() const { return mDmDevPath; };
+    const std::string& getFsUuid() const { return mFsUuid; };
+    dev_t getRawDevice() const { return mRawDevice; };
 
   protected:
     status_t doCreate() override;
diff --git a/model/PublicVolume.cpp b/model/PublicVolume.cpp
index 0a6b351..d1b63a3 100644
--- a/model/PublicVolume.cpp
+++ b/model/PublicVolume.cpp
@@ -15,6 +15,8 @@
  */
 
 #include "PublicVolume.h"
+
+#include "AppFuseUtil.h"
 #include "Utils.h"
 #include "VolumeManager.h"
 #include "fs/Exfat.h"
@@ -167,6 +169,30 @@
 
     dev_t before = GetDevice(mFuseFull);
 
+    bool isFuse = base::GetBoolProperty(kPropFuseSnapshot, false);
+    if (isFuse) {
+        LOG(INFO) << "Mounting public fuse volume";
+        android::base::unique_fd fd;
+        int user_id = getMountUserId();
+        int result = MountUserFuse(user_id, getInternalPath(), stableName, &fd);
+
+        if (result != 0) {
+            LOG(ERROR) << "Failed to mount public fuse volume";
+            return -result;
+        }
+
+        auto callback = getMountCallback();
+        if (callback) {
+            bool is_ready = false;
+            callback->onVolumeChecking(std::move(fd), getPath(), getInternalPath(), &is_ready);
+            if (!is_ready) {
+                return -EIO;
+            }
+        }
+
+        return OK;
+    }
+
     if (!(mFusePid = fork())) {
         if (getMountFlags() & MountFlags::kPrimary) {
             // clang-format off
@@ -229,6 +255,32 @@
     // error code and might cause broken behaviour in applications.
     KillProcessesUsingPath(getPath());
 
+    bool isFuse = base::GetBoolProperty(kPropFuseSnapshot, false);
+    if (isFuse) {
+        // Use UUID as stable name, if available
+        std::string stableName = getId();
+        if (!mFsUuid.empty()) {
+            stableName = mFsUuid;
+        }
+
+        std::string fuse_path(
+                StringPrintf("/mnt/user/%d/%s", getMountUserId(), stableName.c_str()));
+        std::string pass_through_path(
+                StringPrintf("/mnt/pass_through/%d/%s", getMountUserId(), stableName.c_str()));
+        if (UnmountUserFuse(pass_through_path, fuse_path) != OK) {
+            PLOG(INFO) << "UnmountUserFuse failed on public fuse volume";
+            return -errno;
+        }
+        ForceUnmount(kAsecPath);
+        ForceUnmount(mRawPath);
+
+        rmdir(fuse_path.c_str());
+        rmdir(pass_through_path.c_str());
+        rmdir(mRawPath.c_str());
+        mRawPath.clear();
+        return OK;
+    }
+
     ForceUnmount(kAsecPath);
 
     ForceUnmount(mFuseDefault);
diff --git a/model/VolumeBase.cpp b/model/VolumeBase.cpp
index ffc7900..636c065 100644
--- a/model/VolumeBase.cpp
+++ b/model/VolumeBase.cpp
@@ -143,6 +143,16 @@
     return OK;
 }
 
+status_t VolumeBase::setMountCallback(
+        const android::sp<android::os::IVoldMountCallback>& callback) {
+    mMountCallback = callback;
+    return OK;
+}
+
+sp<android::os::IVoldMountCallback> VolumeBase::getMountCallback() const {
+    return mMountCallback;
+}
+
 android::sp<android::os::IVoldListener> VolumeBase::getListener() const {
     if (mSilent) {
         return nullptr;
@@ -176,7 +186,8 @@
 
     auto listener = getListener();
     if (listener) {
-        listener->onVolumeCreated(getId(), static_cast<int32_t>(mType), mDiskId, mPartGuid);
+        listener->onVolumeCreated(getId(), static_cast<int32_t>(mType), mDiskId, mPartGuid,
+                                  mMountUserId);
     }
 
     setState(State::kUnmounted);
diff --git a/model/VolumeBase.h b/model/VolumeBase.h
index 53eeb6f..1d88d1b 100644
--- a/model/VolumeBase.h
+++ b/model/VolumeBase.h
@@ -19,6 +19,7 @@
 
 #include "Utils.h"
 #include "android/os/IVoldListener.h"
+#include "android/os/IVoldMountCallback.h"
 
 #include <cutils/multiuser.h>
 #include <utils/Errors.h>
@@ -87,11 +88,13 @@
     State getState() const { return mState; }
     const std::string& getPath() const { return mPath; }
     const std::string& getInternalPath() const { return mInternalPath; }
+    const std::list<std::shared_ptr<VolumeBase>>& getVolumes() const { return mVolumes; }
 
     status_t setDiskId(const std::string& diskId);
     status_t setPartGuid(const std::string& partGuid);
     status_t setMountFlags(int mountFlags);
     status_t setMountUserId(userid_t mountUserId);
+    status_t setMountCallback(const android::sp<android::os::IVoldMountCallback>& callback);
     status_t setSilent(bool silent);
 
     void addVolume(const std::shared_ptr<VolumeBase>& volume);
@@ -123,6 +126,7 @@
     status_t setInternalPath(const std::string& internalPath);
 
     android::sp<android::os::IVoldListener> getListener() const;
+    android::sp<android::os::IVoldMountCallback> getMountCallback() const;
 
   private:
     /* ID that uniquely references volume while alive */
@@ -147,6 +151,7 @@
     std::string mInternalPath;
     /* Flag indicating that volume should emit no events */
     bool mSilent;
+    android::sp<android::os::IVoldMountCallback> mMountCallback;
 
     /* Volumes stacked on top of this volume */
     std::list<std::shared_ptr<VolumeBase>> mVolumes;