From 77ee43a9fe56db6042d9f91d75cab703f04180e7 Mon Sep 17 00:00:00 2001
From: Daeho Jeong <daehojeong@google.com>
Date: Mon, 21 Oct 2024 13:51:14 -0700
Subject: [PATCH] support f2fs device aliasing feature

We can hold the storage space of one of f2fs multi-device for data
partition, while allowing the space to be used by another purpose.
f2fs will create a sequential and pinned file as a placeholder and it
can be deallocated and returned back to data partition after it is done
with using it. We can create the file, as we define the device with
"exp_alias:" tag in the fstab.

Bug: 336319772
Test: add a device with "exp_alias" tag in fstab
Change-Id: If55730cedd21ec5a40137d2eb723a97df498c9cb
Signed-off-by: Daeho Jeong <daehojeong@google.com>
---
 fs_mgr/fs_mgr.cpp                     |  6 ++++--
 fs_mgr/fs_mgr_format.cpp              | 16 ++++++++++++----
 fs_mgr/libfstab/fstab.cpp             |  1 +
 fs_mgr/libfstab/include/fstab/fstab.h |  1 +
 4 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/fs_mgr/fs_mgr.cpp b/fs_mgr/fs_mgr.cpp
index fbd990b96..fc105d67d 100644
--- a/fs_mgr/fs_mgr.cpp
+++ b/fs_mgr/fs_mgr.cpp
@@ -1603,7 +1603,8 @@ int fs_mgr_mount_all(Fstab* fstab, int mount_mode) {
                                    attempted_entry.fs_type,
                                    attempted_entry.fs_mgr_flags.is_zoned ? "true" : "false",
                                    std::to_string(attempted_entry.length),
-                                   android::base::Join(attempted_entry.user_devices, ' ')},
+                                   android::base::Join(attempted_entry.user_devices, ' '),
+                                   android::base::Join(attempted_entry.device_aliased, ' ')},
                                   nullptr)) {
                         LERROR << "Encryption failed";
                         set_type_property(encryptable);
@@ -1655,7 +1656,8 @@ int fs_mgr_mount_all(Fstab* fstab, int mount_mode) {
                                formattable_entry->fs_type,
                                formattable_entry->fs_mgr_flags.is_zoned ? "true" : "false",
                                std::to_string(formattable_entry->length),
-                               android::base::Join(formattable_entry->user_devices, ' ')},
+                               android::base::Join(formattable_entry->user_devices, ' '),
+                               android::base::Join(formattable_entry->device_aliased, ' ')},
                               nullptr)) {
                     LERROR << "Encryption failed";
                 } else {
diff --git a/fs_mgr/fs_mgr_format.cpp b/fs_mgr/fs_mgr_format.cpp
index 0dde1d374..57e35a275 100644
--- a/fs_mgr/fs_mgr_format.cpp
+++ b/fs_mgr/fs_mgr_format.cpp
@@ -32,6 +32,7 @@
 #include <selinux/android.h>
 #include <selinux/label.h>
 #include <selinux/selinux.h>
+#include <filesystem>
 #include <string>
 
 #include "fs_mgr_priv.h"
@@ -126,7 +127,8 @@ static int format_ext4(const std::string& fs_blkdev, const std::string& fs_mnt_p
 
 static int format_f2fs(const std::string& fs_blkdev, uint64_t dev_sz, bool needs_projid,
                        bool needs_casefold, bool fs_compress, bool is_zoned,
-                       const std::vector<std::string>& user_devices) {
+                       const std::vector<std::string>& user_devices,
+                       const std::vector<int>& device_aliased) {
     if (!dev_sz) {
         int rc = get_dev_sz(fs_blkdev, &dev_sz);
         if (rc) {
@@ -164,9 +166,15 @@ static int format_f2fs(const std::string& fs_blkdev, uint64_t dev_sz, bool needs
     if (is_zoned) {
         args.push_back("-m");
     }
-    for (auto& device : user_devices) {
+    for (size_t i = 0; i < user_devices.size(); i++) {
+        std::string device_name = user_devices[i];
+
         args.push_back("-c");
-        args.push_back(device.c_str());
+        if (device_aliased[i]) {
+            std::filesystem::path path = device_name;
+            device_name += "@" + path.filename().string();
+        }
+        args.push_back(device_name.c_str());
     }
 
     if (user_devices.empty()) {
@@ -191,7 +199,7 @@ int fs_mgr_do_format(const FstabEntry& entry) {
     if (entry.fs_type == "f2fs") {
         return format_f2fs(entry.blk_device, entry.length, needs_projid, needs_casefold,
                            entry.fs_mgr_flags.fs_compress, entry.fs_mgr_flags.is_zoned,
-                           entry.user_devices);
+                           entry.user_devices, entry.device_aliased);
     } else if (entry.fs_type == "ext4") {
         return format_ext4(entry.blk_device, entry.mount_point, needs_projid,
                            entry.fs_mgr_flags.ext_meta_csum);
diff --git a/fs_mgr/libfstab/fstab.cpp b/fs_mgr/libfstab/fstab.cpp
index d344b2d19..6e4cae18f 100644
--- a/fs_mgr/libfstab/fstab.cpp
+++ b/fs_mgr/libfstab/fstab.cpp
@@ -173,6 +173,7 @@ void ParseUserDevices(const std::string& arg, FstabEntry* entry) {
         entry->fs_mgr_flags.is_zoned = true;
     }
     entry->user_devices.push_back(param[1]);
+    entry->device_aliased.push_back(param[0] == "exp_alias" ? 1 : 0);
 }
 
 bool ParseFsMgrFlags(const std::string& flags, FstabEntry* entry) {
diff --git a/fs_mgr/libfstab/include/fstab/fstab.h b/fs_mgr/libfstab/include/fstab/fstab.h
index 21fe01726..070dd9178 100644
--- a/fs_mgr/libfstab/include/fstab/fstab.h
+++ b/fs_mgr/libfstab/include/fstab/fstab.h
@@ -33,6 +33,7 @@ namespace fs_mgr {
 struct FstabEntry {
     std::string blk_device;
     std::vector<std::string> user_devices;
+    std::vector<int> device_aliased;
     std::string logical_partition_name;
     std::string mount_point;
     std::string fs_type;