Add APIs to manage WriteBooster buffer

Five new APIs are introduced to manage and flush
UFS WriteBooster buffer.

Bug: 349648148
Test: StorageManager.*WriteBooster*
Change-Id: I2f82a2d8b08d83a63cbc3da4d9512792b0d472ba
Signed-off-by: Daniel Lee <chullee@google.com>
diff --git a/VoldUtil.cpp b/VoldUtil.cpp
index 082f743..c87b41d 100644
--- a/VoldUtil.cpp
+++ b/VoldUtil.cpp
@@ -15,5 +15,73 @@
  */
 
 #include "VoldUtil.h"
+#include "Utils.h"
+
+#include <libdm/dm.h>
+
+#include <android-base/file.h>
+#include <android-base/logging.h>
+#include <android-base/stringprintf.h>
+#include <android-base/strings.h>
+
+using android::base::Basename;
+using android::base::Realpath;
+using namespace android::dm;
 
 android::fs_mgr::Fstab fstab_default;
+
+static std::string GetUfsHostControllerSysfsPathOnce() {
+    android::fs_mgr::FstabEntry* entry =
+            android::fs_mgr::GetEntryForMountPoint(&fstab_default, DATA_MNT_POINT);
+    if (entry == nullptr) {
+        LOG(ERROR) << "No mount point entry for " << DATA_MNT_POINT;
+        return "";
+    }
+
+    // Handle symlinks.
+    std::string real_path;
+    if (!Realpath(entry->blk_device, &real_path)) {
+        real_path = entry->blk_device;
+    }
+
+    // Handle logical volumes.
+    android::dm::DeviceMapper& dm = android::dm::DeviceMapper::Instance();
+    for (;;) {
+        std::optional<std::string> parent = dm.GetParentBlockDeviceByPath(real_path);
+        if (!parent.has_value()) break;
+        real_path = *parent;
+    }
+
+    std::string path = "/sys/class/block/" + Basename(real_path);
+
+    // Walk up the sysfs directory tree from the partition (e.g, /sys/class/block/sda34)
+    // or from the disk (e.g., /sys/class/block/sda) to reach the UFS host controller's directory
+    // (e.g., /sys/class/block/sda34/../device/../../.. --> /sys/devices/platform/00000000.ufs).
+    if (android::vold::pathExists(path + "/../device")) {
+        path += "/../device/../../..";
+    } else if (android::vold::pathExists(path + "/device")) {
+        path += "/device/../../..";
+    } else {
+        LOG(WARNING) << "Failed to get sysfs_path for user data partition";
+        return "";
+    }
+
+    // Verify the block device is UFS by checking for the presence of "uic_link_state",
+    // which is UFS interconnect layer link state.
+    // If not UFS, return an empty path.
+    if (!android::vold::pathExists(path + "/uic_link_state")) {
+        LOG(ERROR) << "The block device (" << Basename(real_path) << ") of " << DATA_MNT_POINT
+                   << " is not UFS.";
+        return "";
+    }
+
+    LOG(DEBUG) << "The sysfs directory for the ufs host controller is found at " << path;
+    return path;
+}
+
+// get sysfs directory for the ufs host controller containing userdata
+// returns an empty string on failures.
+std::string GetUfsHostControllerSysfsPath() {
+    static std::string ufshc_sysfs_path = GetUfsHostControllerSysfsPathOnce();
+    return ufshc_sysfs_path;
+}