From e7783a98af9456cb5dbc952ce7edb903d24e2915 Mon Sep 17 00:00:00 2001
From: Yi-Yo Chiang <yochiang@google.com>
Date: Tue, 3 Aug 2021 01:02:31 +0800
Subject: [PATCH] fs_mgr: Add fs_mgr_flag overlayfs_remove_missing_lowerdir

If this flag is given, then fs_mgr_mount_overlayfs_fstab_entry() shall
filter out missing directories in the lowerdir= list.

For example,

  test /mnt/vendor/overlay_test overlay \
    ro,lowerdir=/dir1:/dir2:/missing_dir3 \
    first_stage_mount,overlayfs_remove_missing_lowerdir

should mount the overlayfs device with "lowerdir=/dir1:/dir2".

Bug: 186342252
Test: Manual boot test with modified fstab on CF
Change-Id: Id06b37d0c236528cef981e495280b4f4e9c2b4bb
---
 fs_mgr/fs_mgr.cpp                  | 19 ++++++++++++++++++-
 fs_mgr/fs_mgr_fstab.cpp            |  1 +
 fs_mgr/include_fstab/fstab/fstab.h |  1 +
 3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/fs_mgr/fs_mgr.cpp b/fs_mgr/fs_mgr.cpp
index 01c8ad3c4..d38fd7e29 100644
--- a/fs_mgr/fs_mgr.cpp
+++ b/fs_mgr/fs_mgr.cpp
@@ -2322,7 +2322,24 @@ bool fs_mgr_mount_overlayfs_fstab_entry(const FstabEntry& entry) {
         return false;
     }
 
-    auto options = "lowerdir=" + entry.lowerdir;
+    auto lowerdir = entry.lowerdir;
+    if (entry.fs_mgr_flags.overlayfs_remove_missing_lowerdir) {
+        bool removed_any = false;
+        std::vector<std::string> lowerdirs;
+        for (const auto& dir : android::base::Split(entry.lowerdir, ":")) {
+            if (access(dir.c_str(), F_OK)) {
+                PWARNING << __FUNCTION__ << "(): remove missing lowerdir '" << dir << "'";
+                removed_any = true;
+            } else {
+                lowerdirs.push_back(dir);
+            }
+        }
+        if (removed_any) {
+            lowerdir = android::base::Join(lowerdirs, ":");
+        }
+    }
+
+    auto options = "lowerdir=" + lowerdir;
     if (overlayfs_valid_result == OverlayfsValidResult::kOverrideCredsRequired) {
         options += ",override_creds=off";
     }
diff --git a/fs_mgr/fs_mgr_fstab.cpp b/fs_mgr/fs_mgr_fstab.cpp
index d0c89b909..230a703f5 100644
--- a/fs_mgr/fs_mgr_fstab.cpp
+++ b/fs_mgr/fs_mgr_fstab.cpp
@@ -181,6 +181,7 @@ void ParseFsMgrFlags(const std::string& flags, FstabEntry* entry) {
         CheckFlag("fsverity", fs_verity);
         CheckFlag("metadata_csum", ext_meta_csum);
         CheckFlag("fscompress", fs_compress);
+        CheckFlag("overlayfs_remove_missing_lowerdir", overlayfs_remove_missing_lowerdir);
 
 #undef CheckFlag
 
diff --git a/fs_mgr/include_fstab/fstab/fstab.h b/fs_mgr/include_fstab/fstab/fstab.h
index f33768b9d..9a4ed465a 100644
--- a/fs_mgr/include_fstab/fstab/fstab.h
+++ b/fs_mgr/include_fstab/fstab/fstab.h
@@ -86,6 +86,7 @@ struct FstabEntry {
         bool fs_verity : 1;
         bool ext_meta_csum : 1;
         bool fs_compress : 1;
+        bool overlayfs_remove_missing_lowerdir : 1;
     } fs_mgr_flags = {};
 
     bool is_encryptable() const {