remount: Remove errno test & improve messaging of fs_mgr_overlayfs_mount_all

* remount don't check errno after calling fs_mgr_overlayfs_mount_all()
  as we don't report error status through errno anymore.
* fs_mgr_overlayfs_mount_all() returns false if any failure.
* fs_mgr_overlayfs_mount_all() returns true if no overlayfs to mount or
  all overlayfs are either already mounted or mounted successfully.

Bug: 241179247
Bug: 248295731
Test: Treehugger
Change-Id: Ia9c7ac686f6538a9f5da7efc4cda6f28aff056f6
diff --git a/fs_mgr/fs_mgr_overlayfs.cpp b/fs_mgr/fs_mgr_overlayfs.cpp
index 1d5a04b..1d8a452 100644
--- a/fs_mgr/fs_mgr_overlayfs.cpp
+++ b/fs_mgr/fs_mgr_overlayfs.cpp
@@ -1331,22 +1331,22 @@
 }
 
 bool fs_mgr_overlayfs_mount_all(Fstab* fstab) {
-    auto ret = false;
-    if (fs_mgr_overlayfs_invalid()) return ret;
-
+    if (fs_mgr_overlayfs_invalid()) {
+        return false;
+    }
+    auto ret = true;
     auto scratch_can_be_mounted = true;
     for (const auto& entry : fs_mgr_overlayfs_candidate_list(*fstab)) {
         if (fs_mgr_is_verity_enabled(entry)) continue;
         auto mount_point = fs_mgr_mount_point(entry.mount_point);
         if (fs_mgr_overlayfs_already_mounted(mount_point)) {
-            ret = true;
             continue;
         }
         if (scratch_can_be_mounted) {
             scratch_can_be_mounted = false;
             TryMountScratch();
         }
-        if (fs_mgr_overlayfs_mount(mount_point)) ret = true;
+        ret &= fs_mgr_overlayfs_mount(mount_point);
     }
     return ret;
 }
diff --git a/fs_mgr/fs_mgr_remount.cpp b/fs_mgr/fs_mgr_remount.cpp
index 2202fda..a78f945 100644
--- a/fs_mgr/fs_mgr_remount.cpp
+++ b/fs_mgr/fs_mgr_remount.cpp
@@ -451,10 +451,9 @@
     }
 
     // Mount overlayfs.
-    errno = 0;
-    if (!fs_mgr_overlayfs_mount_all(&partitions) && errno) {
-        PLOG(ERROR) << "Can not mount overlayfs for partitions";
-        return BAD_OVERLAY;
+    if (!fs_mgr_overlayfs_mount_all(&partitions)) {
+        LOG(WARNING) << "Cannot mount overlayfs for some partitions";
+        // Continue regardless to handle raw remount case.
     }
 
     // Get actual mounts _after_ overlayfs has been added.