From 491004bbfb67e58040febda9a396455a9a5c90a4 Mon Sep 17 00:00:00 2001
From: Juhyung Park <qkrwngud825@gmail.com>
Date: Tue, 15 Feb 2022 19:18:46 +0900
Subject: [PATCH] init: mount_handler: detect main block device more reliably

Current code is not portable beyond SCSI devices (e.g., UFS).
For example, eMMC and NVMe devices fail due to their extra postfix.

Change its logic to rewind each character until "queue" directory appears.

Test: Confirm md0p1, sda20, nvme0n1p3, mmcblk0p3 are all handled well.
Change-Id: I585ccf2d4a72f6ef8ecb203acdd72a1e32d3e749
Signed-off-by: Juhyung Park <qkrwngud825@gmail.com>
---
 init/mount_handler.cpp | 34 ++++++++++++++++++++++++----------
 1 file changed, 24 insertions(+), 10 deletions(-)

diff --git a/init/mount_handler.cpp b/init/mount_handler.cpp
index f0d8d4569..15ac30590 100644
--- a/init/mount_handler.cpp
+++ b/init/mount_handler.cpp
@@ -25,6 +25,7 @@
 #include <unistd.h>
 
 #include <algorithm>
+#include <filesystem>
 #include <string>
 #include <utility>
 #include <vector>
@@ -32,6 +33,7 @@
 #include <android-base/file.h>
 #include <android-base/logging.h>
 #include <android-base/properties.h>
+#include <android-base/stringprintf.h>
 #include <android-base/strings.h>
 #include <fs_mgr.h>
 #include <fstab/fstab.h>
@@ -39,6 +41,9 @@
 
 #include "epoll.h"
 
+using android::base::Basename;
+using android::base::StringPrintf;
+
 namespace android {
 namespace init {
 
@@ -67,21 +72,30 @@ MountHandlerEntry ParseMount(const std::string& line) {
     return MountHandlerEntry(fields[0], fields[1], fields[2]);
 }
 
+// return dm-4 or dm-8 for dm-4, sda for sda25, or mmcblk0 for mmcblk0p24
+std::string GetRootDisk(std::string blockdev) {
+    if (blockdev.find('/') != std::string::npos) return {};
+
+    std::error_code ec;
+    for (const auto& entry : std::filesystem::directory_iterator("/sys/block", ec)) {
+        const std::string path = entry.path().string();
+        if (std::filesystem::exists(StringPrintf("%s/%s", path.c_str(), blockdev.c_str()))) {
+            return Basename(path);
+        }
+    }
+    if (android::base::StartsWith(blockdev, "dm-")) return blockdev;
+    return {};
+}
+
 void SetMountProperty(const MountHandlerEntry& entry, bool add) {
     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;
     if (add) {
-        value = entry.blk_device.substr(strlen(devblock));
-        if (android::base::StartsWith(value, "sd")) {
-            // All sd partitions inherit their queue characteristics
-            // from the whole device reference.  Strip partition number.
-            auto it = std::find_if(value.begin(), value.end(), [](char c) { return isdigit(c); });
-            if (it != value.end()) value.erase(it, value.end());
-        }
-        auto queue = "/sys/block/" + value + "/queue";
+        value = GetRootDisk(target);
+
         struct stat sb;
-        if (stat(queue.c_str(), &sb) || !S_ISDIR(sb.st_mode)) value = "";
         if (stat(entry.mount_point.c_str(), &sb) || !S_ISDIR(sb.st_mode)) value = "";
         // Clear the noise associated with loopback and APEX.
         if (android::base::StartsWith(value, "loop")) value = "";
@@ -98,7 +112,7 @@ void SetMountProperty(const MountHandlerEntry& entry, bool add) {
     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, entry.blk_device.substr(strlen(devblock)));
+        android::base::SetProperty(dev_mount_prop, target);
     } else {
         android::base::SetProperty(dev_mount_prop, "");
     }