From cb1d0d90afe152012ed0c425f965ea14a91a5a45 Mon Sep 17 00:00:00 2001
From: Yo Chiang <yochiang@google.com>
Date: Mon, 9 Nov 2020 17:45:35 +0800
Subject: [PATCH] Use default DSU slot name when active DSU is empty

If host system is Android Q and guest system is S, then reenable DSU in
the guest system (`adb shell gsi_tool enable -s`) would create an empty
DSU active indicator file.
In this case, use the default slot name "DSU" if DSU active indicator
file is non-existent or empty.

Bug: 172541102
Bug: 168571434
Test: Boot GSI S on Pixel Q with DSU
Test: Verify reenable DSU works
Test: adb shell gsi_tool enable -s && adb reboot
Change-Id: Ie59e4378d1aa4dca085c399a75abd4e662340030
---
 fs_mgr/fs_mgr_fstab.cpp | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs_mgr/fs_mgr_fstab.cpp b/fs_mgr/fs_mgr_fstab.cpp
index 4b7946657..42459ec9c 100644
--- a/fs_mgr/fs_mgr_fstab.cpp
+++ b/fs_mgr/fs_mgr_fstab.cpp
@@ -692,14 +692,18 @@ bool ReadFstabFromFile(const std::string& path, Fstab* fstab) {
         return false;
     }
     if (!is_proc_mounts && !access(android::gsi::kGsiBootedIndicatorFile, F_OK)) {
+        // This is expected to fail if host is android Q, since Q doesn't
+        // support DSU slotting. The DSU "active" indicator file would be
+        // non-existent or empty if DSU is enabled within the guest system.
+        // In that case, just use the default slot name "dsu".
         std::string dsu_slot;
         if (!android::gsi::GetActiveDsu(&dsu_slot)) {
-            // This is expected to fail if host is android Q, since Q doesn't
-            // support DSU slotting.
-            // In that case, just use the default slot name "dsu".
             PWARNING << __FUNCTION__ << "(): failed to get active dsu slot";
+        }
+        if (dsu_slot.empty()) {
             dsu_slot = "dsu";
         }
+
         std::string lp_names;
         ReadFileToString(gsi::kGsiLpNamesFile, &lp_names);
         TransformFstabForDsu(fstab, dsu_slot, Split(lp_names, ","));