From 8a3653cfe2732e27cc223eb3506a2b36bd714ef9 Mon Sep 17 00:00:00 2001
From: luwei9 <luwei9@xiaomi.com>
Date: Wed, 14 Apr 2021 14:34:59 +0800
Subject: [PATCH] [Bugfix]Fix userspace-reboot failure when backing_dev exists
 but zram not swapped on

'/sys/block/zram0/backing_dev' will exist even if zram is not swapped on in some devices. And there is no reason to ensure that zram is swapped on if '/sys/block/zram0/backing_dev' exists. So, if we want to kill backing_dev during userspace reboot, we should check if zram is swapped on first.

TEST: as follow
 - adb root
 - adb shell swapoff /dev/block/zram0
 - adb shell echo 1 > /sys/block/zram0/reset
 - adb shell setprop test.userspace.reboot.flag 1
 - adb reboot userspace
 - (wait reboot ending) adb shell getprop test.userspace.reboot.flag (1 will be show if successful)

Signed-off-by: luwei9 <luwei9@xiaomi.com>
Change-Id: Icca569cf8d64bc024b867dae2ab789fc9e76445a
---
 init/reboot.cpp | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/init/reboot.cpp b/init/reboot.cpp
index d9acee57f..ab0e48e9e 100644
--- a/init/reboot.cpp
+++ b/init/reboot.cpp
@@ -450,10 +450,22 @@ static UmountStat TryUmountAndFsck(unsigned int cmd, bool run_fsck,
 
 // zram is able to use backing device on top of a loopback device.
 // In order to unmount /data successfully, we have to kill the loopback device first
-#define ZRAM_DEVICE   "/dev/block/zram0"
-#define ZRAM_RESET    "/sys/block/zram0/reset"
-#define ZRAM_BACK_DEV "/sys/block/zram0/backing_dev"
+#define ZRAM_DEVICE       "/dev/block/zram0"
+#define ZRAM_RESET        "/sys/block/zram0/reset"
+#define ZRAM_BACK_DEV     "/sys/block/zram0/backing_dev"
+#define ZRAM_INITSTATE    "/sys/block/zram0/initstate"
 static Result<void> KillZramBackingDevice() {
+    std::string zram_initstate;
+    if (!android::base::ReadFileToString(ZRAM_INITSTATE, &zram_initstate)) {
+        return ErrnoError() << "Failed to read " << ZRAM_INITSTATE;
+    }
+
+    zram_initstate.erase(zram_initstate.length() - 1);
+    if (zram_initstate == "0") {
+        LOG(INFO) << "Zram has not been swapped on";
+        return {};
+    }
+
     if (access(ZRAM_BACK_DEV, F_OK) != 0 && errno == ENOENT) {
         LOG(INFO) << "No zram backing device configured";
         return {};