From 6bcabc03d3f16bf267963758552bfcb648107b6a Mon Sep 17 00:00:00 2001
From: Yi-Yo Chiang <yochiang@google.com>
Date: Fri, 18 Feb 2022 22:54:50 +0800
Subject: [PATCH] TransformFstabForDsu: Insert synthesised entry at end of
 mount group

The intention of inserting this synthesised mount entry is for the
FirstStageMount() procedure to eventually fallback to this entry if all
previous mount lines failed.
In order for FirstStageMount() to retry mount, the mount lines have to
be grouped together.
This change ensures that would happen and add test.

Bug: 220074274
Test: atest CtsFsMgrTestCases
Change-Id: Id042a6a6738d27c06a397ef7f4e0977907371c05
---
 fs_mgr/fs_mgr_fstab.cpp      |  7 +++-
 fs_mgr/tests/fs_mgr_test.cpp | 73 ++++++++++++++++++++++++++++++++++++
 2 files changed, 79 insertions(+), 1 deletion(-)

diff --git a/fs_mgr/fs_mgr_fstab.cpp b/fs_mgr/fs_mgr_fstab.cpp
index 0ca1946ad..143e980e4 100644
--- a/fs_mgr/fs_mgr_fstab.cpp
+++ b/fs_mgr/fs_mgr_fstab.cpp
@@ -657,7 +657,12 @@ void TransformFstabForDsu(Fstab* fstab, const std::string& dsu_slot,
             if (partition_ext4 == fstab->end()) {
                 auto new_entry = *GetEntryForMountPoint(fstab, mount_point);
                 new_entry.fs_type = "ext4";
-                fstab->emplace_back(new_entry);
+                auto it = std::find_if(fstab->rbegin(), fstab->rend(),
+                                       [&mount_point](const auto& entry) {
+                                           return entry.mount_point == mount_point;
+                                       });
+                auto end_of_mount_point_group = fstab->begin() + std::distance(it, fstab->rend());
+                fstab->insert(end_of_mount_point_group, new_entry);
             }
         }
     }
diff --git a/fs_mgr/tests/fs_mgr_test.cpp b/fs_mgr/tests/fs_mgr_test.cpp
index eccb902c0..1dbee75ae 100644
--- a/fs_mgr/tests/fs_mgr_test.cpp
+++ b/fs_mgr/tests/fs_mgr_test.cpp
@@ -1104,3 +1104,76 @@ source none6       swap   defaults      readahead_size_kb=0
     EXPECT_TRUE(CompareFlags(flags, entry->fs_mgr_flags));
     EXPECT_EQ(0, entry->readahead_size_kb);
 }
+
+TEST(fs_mgr, TransformFstabForDsu) {
+    TemporaryFile tf;
+    ASSERT_TRUE(tf.fd != -1);
+    std::string fstab_contents = R"fs(
+system /system      erofs   ro  wait,logical,first_stage_mount
+system /system      ext4    ro  wait,logical,first_stage_mount
+vendor /vendor      ext4    ro  wait,logical,first_stage_mount
+data   /data        f2fs    noatime     wait
+)fs";
+
+    ASSERT_TRUE(android::base::WriteStringToFile(fstab_contents, tf.path));
+
+    Fstab fstab;
+    EXPECT_TRUE(ReadFstabFromFile(tf.path, &fstab));
+    TransformFstabForDsu(&fstab, "dsu", {"system_gsi", "userdata_gsi"});
+    ASSERT_EQ(4U, fstab.size());
+
+    auto entry = fstab.begin();
+
+    EXPECT_EQ("/system", entry->mount_point);
+    EXPECT_EQ("system_gsi", entry->blk_device);
+    entry++;
+
+    EXPECT_EQ("/system", entry->mount_point);
+    EXPECT_EQ("system_gsi", entry->blk_device);
+    entry++;
+
+    EXPECT_EQ("/vendor", entry->mount_point);
+    EXPECT_EQ("vendor", entry->blk_device);
+    entry++;
+
+    EXPECT_EQ("/data", entry->mount_point);
+    EXPECT_EQ("userdata_gsi", entry->blk_device);
+    entry++;
+}
+
+TEST(fs_mgr, TransformFstabForDsu_synthesisExt4Entry) {
+    TemporaryFile tf;
+    ASSERT_TRUE(tf.fd != -1);
+    std::string fstab_contents = R"fs(
+system /system      erofs   ro  wait,logical,first_stage_mount
+vendor /vendor      ext4    ro  wait,logical,first_stage_mount
+data   /data        f2fs    noatime     wait
+)fs";
+
+    ASSERT_TRUE(android::base::WriteStringToFile(fstab_contents, tf.path));
+
+    Fstab fstab;
+    EXPECT_TRUE(ReadFstabFromFile(tf.path, &fstab));
+    TransformFstabForDsu(&fstab, "dsu", {"system_gsi", "userdata_gsi"});
+    ASSERT_EQ(4U, fstab.size());
+
+    auto entry = fstab.begin();
+
+    EXPECT_EQ("/system", entry->mount_point);
+    EXPECT_EQ("system_gsi", entry->blk_device);
+    EXPECT_EQ("erofs", entry->fs_type);
+    entry++;
+
+    EXPECT_EQ("/system", entry->mount_point);
+    EXPECT_EQ("system_gsi", entry->blk_device);
+    EXPECT_EQ("ext4", entry->fs_type);
+    entry++;
+
+    EXPECT_EQ("/vendor", entry->mount_point);
+    EXPECT_EQ("vendor", entry->blk_device);
+    entry++;
+
+    EXPECT_EQ("/data", entry->mount_point);
+    EXPECT_EQ("userdata_gsi", entry->blk_device);
+    entry++;
+}