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Enable overlayFS on DSU system

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Enable overlayFS (adb remount) within DSU only if the DM device
scratch_gsi exists. Under DSU mode the backing scratch device of
overlayFS must be scratch_gsi. The scratch_gsi partition must be
created by gsid on the host system and initialized during
first-stage-init. fs_mgr_overlayfs mustn't create any scratch device
for DSU, instead it should just check the existence of the dm node
and initialize the scratch partition (if any).

Bug: 165925766
Test: (In host)
  adb shell gsi_tool create-partition --partition system \
      --size $(du -b system.img | cut -f1) <system.img
  adb shell gsi_tool create-partition --readwirte --partition userdata \
      --size $((8 * 1024 * 1024 * 1024))
  adb shell gsi_tool create-partition --readwirte --partition scratch \
      --size $((200 * 1024 * 1024))
  adb reboot
Test: (In DSU guest)
  # Ensure next reboot is still DSU
  adb shell gsi_tool enable
  adb remount -R
  # Check the output of "adb shell mount"; "/system", "/vendor" ...
  # should be remounted as RW.
Test: adb-remount-test.sh in DSU system
Test: adb-remount-test.sh in normal system
Change-Id: I3267f551313e6b4d4ee63a4f1021040076126e6b
This commit is contained in:
Yo Chiang 2020-10-21 22:25:21 +08:00
parent 346e6792b4
commit 0267bf0e96
1 changed files with 118 additions and 10 deletions
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128
fs_mgr/fs_mgr_overlayfs.cpp
View file

@ -73,6 +73,25 @@ bool fs_mgr_access(const std::string& path) {
return ret;
}
bool fs_mgr_in_recovery() {
// Check the existence of recovery binary instead of using the compile time
// macro, because first-stage-init is compiled with __ANDROID_RECOVERY__
// defined, albeit not in recovery. More details: system/core/init/README.md
return fs_mgr_access("/system/bin/recovery");
}
bool fs_mgr_is_dsu_running() {
// Since android::gsi::CanBootIntoGsi() or android::gsi::MarkSystemAsGsi() is
// never called in recovery, the return value of android::gsi::IsGsiRunning()
// is not well-defined. In this case, just return false as being in recovery
// implies not running a DSU system.
if (fs_mgr_in_recovery()) return false;
auto saved_errno = errno;
auto ret = android::gsi::IsGsiRunning();
errno = saved_errno;
return ret;
}
// determine if a filesystem is available
bool fs_mgr_overlayfs_filesystem_available(const std::string& filesystem) {
std::string filesystems;
@ -171,6 +190,10 @@ constexpr char kScratchImageMetadata[] = "/metadata/gsi/remount/lp_metadata";
// Note: this is meant only for recovery/first-stage init.
bool ScratchIsOnData() {
// The scratch partition of DSU is managed by gsid.
if (fs_mgr_is_dsu_running()) {
return false;
}
return fs_mgr_access(kScratchImageMetadata);
}
@ -464,6 +487,12 @@ bool fs_mgr_overlayfs_teardown_scratch(const std::string& overlay, bool* change)
// umount and delete kScratchMountPoint storage if we have logical partitions
if (overlay != kScratchMountPoint) return true;
// Validation check.
if (fs_mgr_is_dsu_running()) {
LERROR << "Destroying DSU scratch is not allowed.";
return false;
}
auto save_errno = errno;
if (fs_mgr_overlayfs_already_mounted(kScratchMountPoint, false)) {
fs_mgr_overlayfs_umount_scratch();
@ -512,10 +541,13 @@ bool fs_mgr_overlayfs_teardown_scratch(const std::string& overlay, bool* change)
}
bool fs_mgr_overlayfs_teardown_one(const std::string& overlay, const std::string& mount_point,
bool* change) {
bool* change, bool* should_destroy_scratch = nullptr) {
const auto top = overlay + kOverlayTopDir;
if (!fs_mgr_access(top)) return fs_mgr_overlayfs_teardown_scratch(overlay, change);
if (!fs_mgr_access(top)) {
if (should_destroy_scratch) *should_destroy_scratch = true;
return true;
}
auto cleanup_all = mount_point.empty();
const auto partition_name = android::base::Basename(mount_point);
@ -571,7 +603,7 @@ bool fs_mgr_overlayfs_teardown_one(const std::string& overlay, const std::string
PERROR << "rmdir " << top;
}
}
if (cleanup_all) ret &= fs_mgr_overlayfs_teardown_scratch(overlay, change);
if (should_destroy_scratch) *should_destroy_scratch = cleanup_all;
return ret;
}
@ -881,12 +913,29 @@ static std::string GetPhysicalScratchDevice() {
return "";
}
// Note: The scratch partition of DSU is managed by gsid, and should be initialized during
// first-stage-mount. Just check if the DM device for DSU scratch partition is created or not.
static std::string GetDsuScratchDevice() {
auto& dm = DeviceMapper::Instance();
std::string device;
if (dm.GetState(android::gsi::kDsuScratch) != DmDeviceState::INVALID &&
dm.GetDmDevicePathByName(android::gsi::kDsuScratch, &device)) {
return device;
}
return "";
}
// This returns the scratch device that was detected during early boot (first-
// stage init). If the device was created later, for example during setup for
// the adb remount command, it can return an empty string since it does not
// query ImageManager. (Note that ImageManager in first-stage init will always
// use device-mapper, since /data is not available to use loop devices.)
static std::string GetBootScratchDevice() {
// Note: fs_mgr_is_dsu_running() always returns false in recovery or fastbootd.
if (fs_mgr_is_dsu_running()) {
return GetDsuScratchDevice();
}
auto& dm = DeviceMapper::Instance();
// If there is a scratch partition allocated in /data or on super, we
@ -1108,6 +1157,14 @@ static bool CanUseSuperPartition(const Fstab& fstab, bool* is_virtual_ab) {
bool fs_mgr_overlayfs_create_scratch(const Fstab& fstab, std::string* scratch_device,
bool* partition_exists, bool* change) {
// Use the DSU scratch device managed by gsid if within a DSU system.
if (fs_mgr_is_dsu_running()) {
*scratch_device = GetDsuScratchDevice();
*partition_exists = !scratch_device->empty();
*change = false;
return *partition_exists;
}
// Try a physical partition first.
*scratch_device = GetPhysicalScratchDevice();
if (!scratch_device->empty() && fs_mgr_rw_access(*scratch_device)) {
@ -1166,12 +1223,8 @@ bool fs_mgr_overlayfs_setup_scratch(const Fstab& fstab, bool* change) {
bool fs_mgr_overlayfs_invalid() {
if (fs_mgr_overlayfs_valid() == OverlayfsValidResult::kNotSupported) return true;
// in recovery, fastbootd, or gsi mode, not allowed!
if (fs_mgr_access("/system/bin/recovery")) return true;
auto save_errno = errno;
auto ret = android::gsi::IsGsiRunning();
errno = save_errno;
return ret;
// in recovery or fastbootd, not allowed!
return fs_mgr_in_recovery();
}
} // namespace
@ -1314,6 +1367,8 @@ bool fs_mgr_overlayfs_setup(const char* backing, const char* mount_point, bool*
return ret;
}
// Note: This function never returns the DSU scratch device in recovery or fastbootd,
// because the DSU scratch is created in the first-stage-mount, which is not run in recovery.
static bool EnsureScratchMapped(std::string* device, bool* mapped) {
*mapped = false;
*device = GetBootScratchDevice();
@ -1368,6 +1423,42 @@ static void UnmapScratchDevice() {
DestroyLogicalPartition(android::base::Basename(kScratchMountPoint));
}
#if !defined __ANDROID_RECOVERY__
// Provide stubs for non-recovery variant.
static void fs_mgr_overlayfs_teardown_dsu(const char*) {}
#else
// Note: This should only be called from recovery or fastbootd.
static void fs_mgr_overlayfs_teardown_dsu(const char* mount_point) {
std::string dsu_slot;
if (!android::gsi::IsGsiInstalled() || !android::gsi::GetActiveDsu(&dsu_slot) ||
dsu_slot.empty()) {
// Nothing to do if no DSU installation present.
return;
}
auto images = IImageManager::Open("dsu/" + dsu_slot, 10s);
if (!images || !images->BackingImageExists(android::gsi::kDsuScratch)) {
// Nothing to do if DSU scratch device doesn't exist.
return;
}
std::string scratch_device;
images->UnmapImageDevice(android::gsi::kDsuScratch);
if (!images->MapImageDevice(android::gsi::kDsuScratch, 10s, &scratch_device)) {
return;
}
fs_mgr_overlayfs_umount_scratch();
if (fs_mgr_overlayfs_mount_scratch(scratch_device, fs_mgr_overlayfs_scratch_mount_type())) {
fs_mgr_overlayfs_teardown_one(kScratchMountPoint,
mount_point ? fs_mgr_mount_point(mount_point) : "", nullptr);
fs_mgr_overlayfs_umount_scratch();
}
images->UnmapImageDevice(android::gsi::kDsuScratch);
}
#endif
// Returns false if teardown not permitted, errno set to last error.
// If something is altered, set *change.
bool fs_mgr_overlayfs_teardown(const char* mount_point, bool* change) {
@ -1385,9 +1476,20 @@ bool fs_mgr_overlayfs_teardown(const char* mount_point, bool* change) {
fs_mgr_overlayfs_scratch_mount_type());
}
}
bool should_destroy_scratch = false;
for (const auto& overlay_mount_point : kOverlayMountPoints) {
ret &= fs_mgr_overlayfs_teardown_one(
overlay_mount_point, mount_point ? fs_mgr_mount_point(mount_point) : "", change);
overlay_mount_point, mount_point ? fs_mgr_mount_point(mount_point) : "", change,
overlay_mount_point == kScratchMountPoint ? &should_destroy_scratch : nullptr);
}
// Do not attempt to destroy DSU scratch if within a DSU system,
// because DSU scratch partition is managed by gsid.
if (should_destroy_scratch && !fs_mgr_is_dsu_running()) {
// Note: Reaching here in recovery or fastbootd means that a scratch device
// is mounted and cleaned up. Such scratch device mustn't be the DSU scratch,
// because EnsureScratchMapped() is not allowed to map the DSU scratch in
// recovery. In other words, it is safe to destroy the scratch device here.
ret &= fs_mgr_overlayfs_teardown_scratch(kScratchMountPoint, change);
}
if (fs_mgr_overlayfs_valid() == OverlayfsValidResult::kNotSupported) {
// After obligatory teardown to make sure everything is clean, but if
@ -1408,6 +1510,12 @@ bool fs_mgr_overlayfs_teardown(const char* mount_point, bool* change) {
if (unmap) {
UnmapScratchDevice();
}
if (fs_mgr_in_recovery()) {
// Destroy DSU overlay if present.
fs_mgr_overlayfs_teardown_dsu(mount_point);
}
return ret;
}