From c0966c9a1b21a8c34662ebffc7ded763c81f22b7 Mon Sep 17 00:00:00 2001
From: Mark Salyzyn <salyzyn@google.com>
Date: Mon, 26 Nov 2018 09:57:17 -0800
Subject: [PATCH] fs_mgr: overlay: umount scratch more aggressively

For specific teardown operations, if we mount scratch with the
intention of it being temporary to strike out content for a specific
partition, umount it.  Otherwise it could interfer with fastboot.

Test: adb-remount-test.sh
Bug: 120034852
Change-Id: Ieff3f6ea0bcda5eb540e9acf6cab8a56d1453b3e
---
 fs_mgr/fs_mgr_overlayfs.cpp | 29 +++++++++++++++++++----------
 1 file changed, 19 insertions(+), 10 deletions(-)

diff --git a/fs_mgr/fs_mgr_overlayfs.cpp b/fs_mgr/fs_mgr_overlayfs.cpp
index bef46e1e1..edada175a 100644
--- a/fs_mgr/fs_mgr_overlayfs.cpp
+++ b/fs_mgr/fs_mgr_overlayfs.cpp
@@ -395,6 +395,18 @@ bool fs_mgr_overlayfs_has_logical(const fstab* fstab) {
     return false;
 }
 
+void fs_mgr_overlayfs_umount_scratch() {
+    // Lazy umount will allow us to move on and possibly later
+    // establish a new fresh mount without requiring a reboot should
+    // the developer wish to restart.  Old references should melt
+    // away or have no data.  Main goal is to shut the door on the
+    // current overrides with an expectation of a subsequent reboot,
+    // thus any errors here are ignored.
+    umount2(kScratchMountPoint.c_str(), MNT_DETACH);
+    LINFO << "umount(" << kScratchMountPoint << ")";
+    rmdir(kScratchMountPoint.c_str());
+}
+
 // reduce 'DM_DEV_STATUS failed for scratch: No such device or address' noise
 std::string scratch_device_cache;
 
@@ -408,13 +420,7 @@ bool fs_mgr_overlayfs_teardown_scratch(const std::string& overlay, bool* change)
 
     auto save_errno = errno;
     if (fs_mgr_overlayfs_already_mounted(kScratchMountPoint, false)) {
-        // Lazy umount will allow us to move on and possibly later
-        // establish a new fresh mount without requiring a reboot should
-        // the developer wish to restart.  Old references should melt
-        // away or have no data.  Main goal is to shut the door on the
-        // current overrides with an expectation of a subsequent reboot,
-        // thus any errors here are ignored.
-        umount2(kScratchMountPoint.c_str(), MNT_DETACH);
+        fs_mgr_overlayfs_umount_scratch();
     }
     auto builder = MetadataBuilder::New(super_device, slot_number);
     if (!builder) {
@@ -773,8 +779,7 @@ bool fs_mgr_overlayfs_mount_all(fstab* fstab) {
                 fs_mgr_overlayfs_mount_scratch(scratch_device,
                                                fs_mgr_overlayfs_scratch_mount_type()) &&
                 !fs_mgr_access(kScratchMountPoint + kOverlayTopDir)) {
-                umount2(kScratchMountPoint.c_str(), MNT_DETACH);
-                rmdir(kScratchMountPoint.c_str());
+                fs_mgr_overlayfs_umount_scratch();
             }
         }
         if (fs_mgr_overlayfs_mount(mount_point)) ret = true;
@@ -867,6 +872,7 @@ bool fs_mgr_overlayfs_teardown(const char* mount_point, bool* change) {
     auto ret = true;
     // If scratch exists, but is not mounted, lets gain access to clean
     // specific override entries.
+    auto mount_scratch = false;
     if ((mount_point != nullptr) && !fs_mgr_overlayfs_already_mounted(kScratchMountPoint, false)) {
         auto scratch_device = fs_mgr_overlayfs_scratch_device();
         if (scratch_device.empty()) {
@@ -876,7 +882,8 @@ bool fs_mgr_overlayfs_teardown(const char* mount_point, bool* change) {
             CreateLogicalPartition(super_device, slot_number, partition_name, true, 0s,
                                    &scratch_device);
         }
-        fs_mgr_overlayfs_mount_scratch(scratch_device, fs_mgr_overlayfs_scratch_mount_type());
+        mount_scratch = fs_mgr_overlayfs_mount_scratch(scratch_device,
+                                                       fs_mgr_overlayfs_scratch_mount_type());
     }
     for (const auto& overlay_mount_point : kOverlayMountPoints) {
         ret &= fs_mgr_overlayfs_teardown_one(overlay_mount_point, mount_point ?: "", change);
@@ -894,6 +901,8 @@ bool fs_mgr_overlayfs_teardown(const char* mount_point, bool* change) {
         PERROR << "teardown";
         ret = false;
     }
+    if (mount_scratch) fs_mgr_overlayfs_umount_scratch();
+
     return ret;
 }