Re: [PATCH v6 2/2] init/do_mounts.c: create second mount for initramfs

From: Menglong Dong <menglong8.dong@gmail.com>
To: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
	Kees Cook <keescook@chromium.org>,
	Sami Tolvanen <samitolvanen@google.com>,
	johan@kernel.org, ojeda@kernel.org, jeyu@kernel.org,
	masahiroy@kernel.org, joe@perches.com, Jan Kara <jack@suse.cz>,
	hare@suse.de, Jens Axboe <axboe@kernel.dk>,
	tj@kernel.org, gregkh@linuxfoundation.org, song@kernel.org,
	NeilBrown <neilb@suse.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	Barret Rhoden <brho@google.com>,
	f.fainelli@gmail.com, palmerdabbelt@google.com,
	wangkefeng.wang@huawei.com,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	vbabka@suse.cz, Alexander Potapenko <glider@google.com>,
	pmladek@suse.com, johannes.berg@intel.com,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	jojing64@gmail.com, terrelln@fb.com, geert@linux-m68k.org,
	linux-fsdevel@vger.kernel.org,
	LKML <linux-kernel@vger.kernel.org>,
	Luis Chamberlain <mcgrof@kernel.org>,
	arnd@arndb.de, Chris Down <chris@chrisdown.name>,
	mingo@kernel.org, Bjorn Helgaas <bhelgaas@google.com>,
	Josh Triplett <josh@joshtriplett.org>
Subject: Re: [PATCH v6 2/2] init/do_mounts.c: create second mount for initramfs
Date: Wed, 16 Jun 2021 20:57:56 -0700	[thread overview]
Message-ID: <20210617035756.GA228302@www> (raw)
In-Reply-To: <20210607121524.GB3896@www>

Hello,

On Mon, Jun 07, 2021 at 05:15:24AM -0700, menglong8.dong@gmail.com wrote:
> On Mon, Jun 07, 2021 at 12:31:47PM +0200, Christian Brauner wrote:
> > On Sat, Jun 05, 2021 at 10:47:07PM +0800, Menglong Dong wrote:
> [...]
> > > 
> > > I think it's necessary, as I explained in the third patch. When the rootfs
> > > is a block device, ramfs is used in init_mount_tree() unconditionally,
> > > which can be seen from the enable of is_tmpfs.
> > > 
> > > That makes sense, because rootfs will not become the root if a block
> > > device is specified by 'root' in boot cmd, so it makes no sense to use
> > > tmpfs, because ramfs is more simple.
> > > 
> > > Here, I make rootfs as ramfs for the same reason: the first mount is not
> > > used as the root, so make it ramfs which is more simple.
> > 
> > Ok. If you don't mind I'd like to pull and test this before moving
> > further. (Btw, I talked about this at Plumbers before btw.)
> > What did you use for testing this? Any way you can share it?
> 

I notice that it have been ten days, and is it ok to move a little
further? (knock-knock :/)

Thanks!
Menglong Dong

> Ok, no problem definitely. I tested this function in 3 way mainly:
> 
> 1. I debug the kernel with qemu and gdb, and trace the the whole
>    process, to ensure that there is no abnormal situation.
> 2. I tested pivot_root() in initramfs and ensured that it can be
>    used normally. What's more, I also tested docker and ensured
>    container can run normally without 'DOCKER_RAMDISK=yes' set in
>    initramfs.
> 3. I tried to enable and disable CONFIG_INITRAMFS_MOUNT, and
>    ensured that the system can boot successfully from initramfs, initrd
>    and sda.
> 
> What's more, our team is going to test it comprehensively, such as
> ltp, etc.
> 
> Thanks!
> Menglong Dong                                                                                                                                                         
> 