前言
众所周知，咱是老牌小米8屏幕指纹版钉子户了
咱一直想给这个机子上个erofs（关于erofs是什么请自行搜索
但是经过查阅得知erofs是在5.10被加入到Linux内核中的，也就是说咱4.9得手动集成
准备材料
- Android ROM源码：这里使用的是LineageOS 22.0
- Android Kernel源码：这里咱用的是LineageOS官方小米845内核：LineageOS/android_kernel_xiaomi_sdm845
- 设备树：这里使用的是LineageOS官方设备树，包含sdm845-common部分（LineageOS/android_device_xiaomi_sdm845-common）和device-specific部分（LineageOS/android_device_xiaomi_equuleus）
- 编译服务器
开整
部署Android ROM编译环境就不说了，网上一搜一大片，把ROM源码、设备树、内核源码下载下来放到对应位置
为内核添加erofs支持
此处代码pick from ReallySnow的msm-4.9内核（谢谢ReallySnow大佬的支持！），可参考如下分支：
- https://github.com/ReallySnow/msm-4.9/tree/erofs
- https://github.com/YoriInstitute/android_kernel_xiaomi_sdm845/tree/lineage-22.0-erofs
pick之前要先处理lz4压缩部分代码的冲突。详细Relation chain可参考：
咱尝试将改造提交给LineageOS官方但是很显然没被合并x
pick完更改后在内核的defconfig文件中开启erofs支持：
打开$KERNEL_SOURCE/arch/arm64/configs/vendor/xiaomi/mi845_defconfig并添加：CONFIG_EROFS_FS=y：
commit 7ae5caab2c15982b3d3821c97e2f2e6126ca1281 (HEAD -> erofs, refs/published/erofs)
Author: KaguraiYoRoy <neko@yori.moe>
Date: Tue Dec 24 22:49:07 2024 +0800
arch: arm64: configs: mi845: Enable CONFIG_EROFS_FS
Change-Id: Ie387b03bde54700d73ccf19f0baf4db62526cc8f
diff --git a/arch/arm64/configs/vendor/xiaomi/mi845_defconfig b/arch/arm64/configs/vendor/xiaomi/mi845_defconfig
index 7684be360d98..69ea580fdb11 100644
--- a/arch/arm64/configs/vendor/xiaomi/mi845_defconfig
+++ b/arch/arm64/configs/vendor/xiaomi/mi845_defconfig
@@ -651,3 +651,4 @@ CONFIG_SOUNDWIRE_WCD_CTRL=y
CONFIG_WCD9XXX_CODEC_CORE=y
CONFIG_WCD_DSP_GLINK=y
CONFIG_WCD_SPI_AC=y
+CONFIG_EROFS_FS=y
\ No newline at end of file修改分区文件系统和fstab
打开设备树中板级配置文件把要改为erofs的分区的文件系统改为erofs，示例中的配置文件在$WORKING_DIR/device/xiaomi/sdm845-common/BoardConfigCommon.mk：
commit 0fce86fb40ca637a8563bef6192afaea1658c881 (HEAD -> erofs, refs/published/erofs)
Author: KaguraiYoRoy <neko@yori.moe>
Date: Tue Dec 24 23:37:50 2024 +0800
sdm845-common: Switch to erofs
Change-Id: I9a8d6de4dcb79cd6bc177451ce3cbc4682748501
diff --git a/BoardConfigCommon.mk b/BoardConfigCommon.mk
index cf73d39..700592f 100644
--- a/BoardConfigCommon.mk
+++ b/BoardConfigCommon.mk
@@ -78,11 +78,11 @@ BOARD_CACHEIMAGE_PARTITION_SIZE := 268435456
BOARD_USERDATAIMAGE_PARTITION_SIZE := 57453555712
BOARD_CACHEIMAGE_FILE_SYSTEM_TYPE := ext4
-BOARD_ODMIMAGE_FILE_SYSTEM_TYPE := ext4
+BOARD_ODMIMAGE_FILE_SYSTEM_TYPE := erofs
BOARD_PRODUCTIMAGE_FILE_SYSTEM_TYPE := ext4
BOARD_SYSTEMIMAGE_FILE_SYSTEM_TYPE := ext4
BOARD_SYSTEM_EXTIMAGE_FILE_SYSTEM_TYPE := ext4
-BOARD_VENDORIMAGE_FILE_SYSTEM_TYPE := ext4
+BOARD_VENDORIMAGE_FILE_SYSTEM_TYPE := erofs
BOARD_FLASH_BLOCK_SIZE := 262144 # (BOARD_KERNEL_PAGESIZE * 64)
修改机器fstab文件，此处在$WORKING_DIR/device/xiaomi/equuleus/rootdir/fstab.qcom，将挂载文件系统改为erofs，挂载参数仅保留一个ro即可：
commit d66bfc8fe722f7368ef56835d35fb88b904e10fb (HEAD -> erofs, refs/published/erofs)
Author: KaguraiYoRoy <neko@yori.moe>
Date: Tue Dec 24 23:40:08 2024 +0800
equuleus: Update fstab for erofs
Change-Id: I814eab1dd77cf2c184ebd398cc4914785bc37ad6
diff --git a/rootdir/etc/fstab.qcom b/rootdir/etc/fstab.qcom
index 7aca90a..685ec84 100644
--- a/rootdir/etc/fstab.qcom
+++ b/rootdir/etc/fstab.qcom
@@ -6,8 +6,8 @@
system /system ext4 ro,barrier=1,discard wait,logical,first_stage_mount
system_ext /system_ext ext4 ro,barrier=1,discard wait,logical,first_stage_mount
product /product ext4 ro,barrier=1,discard wait,logical,first_stage_mount
-vendor /vendor ext4 ro,barrier=1,discard wait,logical,first_stage_mount
-odm /odm ext4 ro,barrier=1,discard wait,logical,first_stage_mount
+vendor /vendor erofs ro wait,logical,first_stage_mount
+odm /odm erofs ro wait,logical,first_stage_mount
/dev/block/bootdevice/by-name/userdata /data ext4 noatime,nosuid,nodev,barrier=0,noauto_da_alloc latemount,wait,check,fileencryption=ice,quota
/dev/block/bootdevice/by-name/modem /vendor/firmware_mnt vfat ro,shortname=lower,uid=0,gid=1000,dmask=227,fmask=337,context=u:object_r:firmware_file:s0 wait
/dev/block/bootdevice/by-name/dsp /vendor/dsp ext4 ro,nosuid,nodev,barrier=1 wait最后编译并刷入，如果不出意外的话就能启动进系统了。
特别注意
- LineageOS官方对我这款机型做了动态分区改造，上述设备树的修改可能并不适用于你的机型
- erofs为只读文件系统，如果后期要刷Gapps，请勿改造
system、system_ext、product这三个分区
常见问题
- 开机进入fastboot：检查fstab是否修改正确
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