linux-kernel - Re: [PATCH v3 0/3] init/initramfs.c: make initramfs support pivot

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Message-ID: <CADxym3Ya3Jv_tUMJyq+ymd8m1_S-KezqNDfsLtMcJCXtDytBzA@mail.gmail.com>
Date:   Tue, 1 Jun 2021 21:55:33 +0800
From:   Menglong Dong <menglong8.dong@...il.com>
To:     Luis Chamberlain <mcgrof@...nel.org>,
        Josh Triplett <josh@...htriplett.org>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Sami Tolvanen <samitolvanen@...gle.com>, ojeda@...nel.org,
        johan@...nel.org, jeyu@...nel.org, masahiroy@...nel.org,
        Menglong Dong <dong.menglong@....com.cn>, joe@...ches.com,
        Jens Axboe <axboe@...nel.dk>, Jan Kara <jack@...e.cz>,
        hare@...e.de, tj@...nel.org, gregkh@...uxfoundation.org,
        song@...nel.org, NeilBrown <neilb@...e.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        f.fainelli@...il.com, wangkefeng.wang@...wei.com, arnd@...db.de,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Barret Rhoden <brho@...gle.com>,
        Steven Rostedt <rostedt@...dmis.org>, vbabka@...e.cz,
        pmladek@...e.com, Alexander Potapenko <glider@...gle.com>,
        Chris Down <chris@...isdown.name>, jojing64@...il.com,
        "Eric W. Biederman" <ebiederm@...ssion.com>, mingo@...nel.org,
        terrelln@...com, geert@...ux-m68k.org,
        linux-fsdevel@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH v3 0/3] init/initramfs.c: make initramfs support pivot_root

Hello!

What's the status or fate of this patch? Does anyone do an in-depth
study of this field? Knock-knock~

On Sat, May 29, 2021 at 10:26 AM Masami Hiramatsu <mhiramat@...nel.org> wrote:
>
> Hi Menglong,
>
> On Fri, 28 May 2021 22:37:59 +0800
> menglong8.dong@...il.com wrote:
>
> > From: Menglong Dong <dong.menglong@....com.cn>
> >
> > 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@zte.com.cn/)
> > 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 V2:
> >
> > In the first patch, I use vfs_path_lookup() in init_eaccess() to make the
> > path lookup follow the mount on '/'. After this, the problem reported by
> > Masami Hiramatsu is solved. Thanks for your report :/
>
> Thank you for the fix, I confirmed that the issue has been solved with this.
>
> Tested-by: Masami Hiramatsu <mhiramat@...nel.org>
>
> for this series.
>
> Regards,
>
>
> >
> >
> > 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'.
> >
> >
> >
> > Menglong Dong (3):
> >   init/main.c: introduce function ramdisk_exec_exist()
> >   init/do_cmounts.c: introduce 'user_root' for initramfs
> >   init/do_mounts.c: fix rootfs_fs_type with ramfs
> >
> >  fs/init.c            |  11 ++++-
> >  include/linux/init.h |   5 ++
> >  init/do_mounts.c     | 109 +++++++++++++++++++++++++++++++++++++++++++
> >  init/do_mounts.h     |  18 ++++++-
> >  init/initramfs.c     |  10 ++++
> >  init/main.c          |   7 ++-
> >  usr/Kconfig          |  10 ++++
> >  7 files changed, 166 insertions(+), 4 deletions(-)
> >
> > --
> > 2.32.0.rc0
> >
>
>
> --
> Masami Hiramatsu <mhiramat@...nel.org>

Thanks!
Menglong Dong