commit 120f6b260c268c677735fcef434f9480223725ed
author Jaegeuk Kim <jaegeuk@google.com> Fri Mar 04 15:06:02 2022 -0800
committer Jaegeuk Kim <jaegeuk@google.com> Mon Mar 14 16:59:52 2022 -0700
tree 21c4e42e9e03ef180502a15843db1a676adead01
parent 491004bbfb67e58040febda9a396455a9a5c90a4

Init: add dev.mnt.blk.bootdevice to access device sysfs

This patch adds a new property, 'dev.mnt.root.<mount_point>', which provides,
for example of /data,

1. dm-N
  dev.mnt.dev.data = dm-N
  dev.mnt.blk.data = sdaN or mmcblk0pN
  dev.mnt.rootdisk.data = sda or mmcblk0

2. sdaN or mmcblk0pN
  dev.mnt.dev.data = sdaN or mmcblk0pN
  dev.mnt.blk.data = sdaN or mmcblk0pN
  dev.mnt.rootdisk.data = sda or mmcblk0

Signed-off-by: Jaegeuk Kim <jaegeuk@google.com>
Change-Id: I0a58a62d416f966f26b5de04112c2f9a7eceb22c

init/mount_handler.cpp

diff --git a/init/mount_handler.cpp b/init/mount_handler.cpp
index 15ac305..227ce2f 100644
--- a/init/mount_handler.cpp
+++ b/init/mount_handler.cpp
@@ -72,8 +72,25 @@
     return MountHandlerEntry(fields[0], fields[1], fields[2]);
 }
 
-// return dm-4 or dm-8 for dm-4, sda for sda25, or mmcblk0 for mmcblk0p24
+// return sda25 for dm-4, sda25 for sda25, or mmcblk0p24 for mmcblk0p24
+std::string GetDiskPart(std::string blockdev) {
+    if (blockdev.find('/') != std::string::npos) return {};
+
+    while (android::base::StartsWith(blockdev, "dm-")) {
+        auto& dm = dm::DeviceMapper::Instance();
+        std::optional<std::string> parent = dm.GetParentBlockDeviceByPath("/dev/block/" + blockdev);
+        if (parent) {
+            blockdev = android::base::Basename(*parent);
+        } else {
+            return {};
+        }
+    }
+    return blockdev;
+}
+
+// return sda for sda25, or mmcblk0 for mmcblk0p24
 std::string GetRootDisk(std::string blockdev) {
+    if (blockdev.empty()) return {};
     if (blockdev.find('/') != std::string::npos) return {};
 
     std::error_code ec;
@@ -83,7 +100,6 @@
             return Basename(path);
         }
     }
-    if (android::base::StartsWith(blockdev, "dm-")) return blockdev;
     return {};
 }
 
@@ -91,31 +107,47 @@
     static constexpr char devblock[] = "/dev/block/";
     if (!android::base::StartsWith(entry.blk_device, devblock)) return;
     auto target = entry.blk_device.substr(strlen(devblock));
-    std::string value;
+    std::string diskpart, rootdisk;
     if (add) {
-        value = GetRootDisk(target);
+        diskpart = GetDiskPart(target);
+        rootdisk = GetRootDisk(diskpart);
 
         struct stat sb;
-        if (stat(entry.mount_point.c_str(), &sb) || !S_ISDIR(sb.st_mode)) value = "";
+        if (stat(entry.mount_point.c_str(), &sb) || !S_ISDIR(sb.st_mode)) rootdisk = "";
         // Clear the noise associated with loopback and APEX.
-        if (android::base::StartsWith(value, "loop")) value = "";
-        if (android::base::StartsWith(entry.mount_point, "/apex/")) value = "";
+        if (android::base::StartsWith(target, "loop")) rootdisk = "";
+        if (android::base::StartsWith(entry.mount_point, "/apex/")) rootdisk = "";
     }
     auto mount_prop = entry.mount_point;
     if (mount_prop == "/") mount_prop = "/root";
     std::replace(mount_prop.begin(), mount_prop.end(), '/', '.');
     auto blk_mount_prop = "dev.mnt.blk" + mount_prop;
     auto dev_mount_prop = "dev.mnt.dev" + mount_prop;
-    // Set property even if its value does not change to trigger 'on property:'
+    auto rootdisk_mount_prop = "dev.mnt.rootdisk" + mount_prop;
+    // Set property even if its rootdisk does not change to trigger 'on property:'
     // handling, except for clearing non-existent or already clear property.
     // Goal is reduction of empty properties and associated triggers.
-    if (value.empty() && android::base::GetProperty(blk_mount_prop, "").empty()) return;
-    android::base::SetProperty(blk_mount_prop, value);
-    if (!value.empty()) {
-        android::base::SetProperty(dev_mount_prop, target);
-    } else {
+    if (rootdisk.empty() && android::base::GetProperty(blk_mount_prop, "").empty()) return;
+
+    if (rootdisk.empty()) {
+        android::base::SetProperty(blk_mount_prop, "");
         android::base::SetProperty(dev_mount_prop, "");
+        android::base::SetProperty(rootdisk_mount_prop, "");
+        return;
     }
+
+    // 1. dm-N
+    //  dev.mnt.dev.data = dm-N
+    //  dev.mnt.blk.data = sdaN or mmcblk0pN
+    //  dev.mnt.rootdisk.data = sda or mmcblk0
+    //
+    // 2. sdaN or mmcblk0pN
+    //  dev.mnt.dev.data = sdaN or mmcblk0pN
+    //  dev.mnt.blk.data = sdaN or mmcblk0pN
+    //  dev.mnt.rootdisk.data = sda or mmcblk0
+    android::base::SetProperty(dev_mount_prop, target);
+    android::base::SetProperty(blk_mount_prop, diskpart);
+    android::base::SetProperty(rootdisk_mount_prop, rootdisk);
 }
 
 }  // namespace