commit 491004bbfb67e58040febda9a396455a9a5c90a4
author Juhyung Park <qkrwngud825@gmail.com> Tue Feb 15 19:18:46 2022 +0900
committer Jaegeuk Kim <jaegeuk@google.com> Mon Mar 14 16:59:52 2022 -0700
tree b145686f846cd4f2011e8584e5ed6aa35a75e4a6
parent 852111eea4eaf3c56e4ca9296a42b5b2a10df712

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

diff --git a/init/mount_handler.cpp b/init/mount_handler.cpp
index f0d8d45..15ac305 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 @@
     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 @@
     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, "");
     }