Re: [PATCH v2 0/3] init/initramfs.c: make initramfs support pivot_root

[Josh Triplett]

On Tue, May 25, 2021 at 10:15:21PM +0800, menglong8.dong@xxxxxxxxx wrote:
> From: Menglong Dong <dong.menglong@xxxxxxxxxx>
> 
> As Luis Chamberlain suggested, I split the patch:
> [init/initramfs.c: make initramfs support pivot_root]
> (https://lore.kernel.org/linux-fsdevel/20210520154244.20209-1-dong.menglong@xxxxxxxxxx/)
> into three.
> 
> The goal of the series patches is to make pivot_root() support initramfs.
> 
> In the first patch, I introduce the function ramdisk_exec_exist(), which
> is used to check the exist of 'ramdisk_execute_command' in LOOKUP_DOWN
> lookup mode.
> 
> In the second patch, I create a second mount, which is called
> 'user root', and make it become the root. Therefore, the root has a
> parent mount, and it can be umounted or pivot_root.
> 
> In the third patch, I fix rootfs_fs_type with ramfs, as it is not used
> directly any more, and it make no sense to switch it between ramfs and
> tmpfs, just fix it with ramfs to simplify the code.
> 
> Changes since V1:
> 
> In the first patch, I add the flag LOOKUP_DOWN to init_eaccess(), to make
> it support the check of filesystem mounted on '/'.
> 
> In the second patch, I control 'user root' with kconfig option
> 'CONFIG_INITRAMFS_USER_ROOT', and add some comments, as Luis Chamberlain
> suggested.
> 
> In the third patch, I make 'rootfs_fs_type' in control of
> 'CONFIG_INITRAMFS_USER_ROOT'.

This looks much better, thank you; this addresses all my concerns with
v1. I appreciate having the config option to control this as well.