fs_mgr: Add OverlayMountPoints() to get the list of overlayfs backing storage
Remove kOverlayMountPoints; add OverlayMountPoints().
Fix a regression where if host system didn't install a scratch_gsi
partition and physical /cache partition is mounted, then DSU guest
system could use /cache as its overlayfs backing storage. This is
generally unwanted as the /cache partition could be shared between host
and guest.
Dynamically return the list of overlayfs backing storage candidates, so
we don't accidentally fall back to use /cache storage within a DSU
system.
Bug: 165925766
Bug: 179980369
Test: 1. Prepare a DUT that have a physical cache partition, such as
cuttlefish.
2. Install a DSU system, and unsure that scratch_gsi is not installed.
3. Reboot into DSU, verify that adb remount fails and overlayfs
scratch is not created under /cache.
Change-Id: I1815ac5367c0aac8614aeaabebe0e2cb91cbe161
diff --git a/fs_mgr/fs_mgr_overlayfs.cpp b/fs_mgr/fs_mgr_overlayfs.cpp
index 388c296..cdbadc9 100644
--- a/fs_mgr/fs_mgr_overlayfs.cpp
+++ b/fs_mgr/fs_mgr_overlayfs.cpp
@@ -125,10 +125,38 @@
namespace {
+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;
+}
+
// list of acceptable overlayfs backing storage
const auto kScratchMountPoint = "/mnt/scratch"s;
const auto kCacheMountPoint = "/cache"s;
-const std::vector<const std::string> kOverlayMountPoints = {kScratchMountPoint, kCacheMountPoint};
+
+std::vector<const std::string> OverlayMountPoints() {
+ // Never fallback to legacy cache mount point if within a DSU system,
+ // because running a DSU system implies the device supports dynamic
+ // partitions, which means legacy cache mustn't be used.
+ if (fs_mgr_is_dsu_running()) {
+ return {kScratchMountPoint};
+ }
+ return {kScratchMountPoint, kCacheMountPoint};
+}
// Return true if everything is mounted, but before adb is started. Right
// after 'trigger load_persist_props_action' is done.
@@ -169,25 +197,6 @@
(vst.f_bfree * vst.f_bsize) >= kSizeThreshold;
}
-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;
-}
-
const auto kPhysicalDevice = "/dev/block/by-name/"s;
constexpr char kScratchImageMetadata[] = "/metadata/gsi/remount/lp_metadata";
@@ -300,7 +309,7 @@
std::string fs_mgr_get_overlayfs_candidate(const std::string& mount_point) {
if (!fs_mgr_is_dir(mount_point)) return "";
const auto base = android::base::Basename(mount_point) + "/";
- for (const auto& overlay_mount_point : kOverlayMountPoints) {
+ for (const auto& overlay_mount_point : OverlayMountPoints()) {
auto dir = overlay_mount_point + kOverlayTopDir + "/" + base;
auto upper = dir + kUpperName;
if (!fs_mgr_is_dir(upper)) continue;
@@ -1344,7 +1353,7 @@
if (candidates.empty()) return ret;
std::string dir;
- for (const auto& overlay_mount_point : kOverlayMountPoints) {
+ for (const auto& overlay_mount_point : OverlayMountPoints()) {
if (backing && backing[0] && (overlay_mount_point != backing)) continue;
if (overlay_mount_point == kScratchMountPoint) {
if (!fs_mgr_overlayfs_setup_scratch(fstab, change)) continue;
@@ -1465,7 +1474,7 @@
}
}
bool should_destroy_scratch = false;
- for (const auto& overlay_mount_point : kOverlayMountPoints) {
+ for (const auto& overlay_mount_point : OverlayMountPoints()) {
ret &= fs_mgr_overlayfs_teardown_one(
overlay_mount_point, mount_point ? fs_mgr_mount_point(mount_point) : "", change,
overlay_mount_point == kScratchMountPoint ? &should_destroy_scratch : nullptr);
@@ -1569,7 +1578,7 @@
constexpr bool* ignore_change = nullptr;
// Teardown legacy overlay mount points that's not backed by a scratch device.
- for (const auto& overlay_mount_point : kOverlayMountPoints) {
+ for (const auto& overlay_mount_point : OverlayMountPoints()) {
if (overlay_mount_point == kScratchMountPoint) {
continue;
}