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Date: Wed, 17 Jul 2013 17:15:29 -0700 (PDT)
From: Hugh Dickins <hughd@google.com>
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To: Andrew Morton <akpm@linux-foundation.org>
cc: Rob Landley <rob@landley.net>, linux-kernel@vger.kernel.org,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Hugh Dickins <hughd@google.com>, Jeff Layton <jlayton@redhat.com>,
        Jens Axboe <axboe@kernel.dk>, Jim Cromie <jim.cromie@gmail.com>,
        linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
        Rusty Russell <rusty@rustcorp.com.au>, Sam Ravnborg <sam@ravnborg.org>,
        Stephen Warren <swarren@nvidia.com>
Subject: Re: [PATCH 0/5] initmpfs v2: use tmpfs instead of ramfs for rootfs
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On Wed, 17 Jul 2013, Andrew Morton wrote:
> On Tue, 16 Jul 2013 08:31:13 -0700 (PDT) Rob Landley <rob@landley.net> wrote:
> 
> > Use tmpfs for rootfs when CONFIG_TMPFS=y and there's no root=.
> > Specify rootfstype=ramfs to get the old initramfs behavior.
> > 
> > The previous initramfs code provided a fairly crappy root filesystem:
> > didn't let you --bind mount directories out of it, reported zero
> > size/usage so it didn't show up in "df" and couldn't run things like
> > rpm that query available space before proceeding, would fill up all
> > available memory and panic the system if you wrote too much to it...
> 
> The df problem and the mount --bind thing are ramfs issues, are they
> not?  Can we fix them?  If so, that's a less intrusive change, and we
> also get a fixed ramfs.

I'll leave others to comment on "mount --bind", but with regard to "df":
yes, we could enhance ramfs with accounting such as tmpfs has, to allow
it to support non-0 "df".  We could have done so years ago; but have
always preferred to leave ramfs as minimal, than import tmpfs features
into it one by one.

I prefer Rob's approach of making tmpfs usable for rootfs.

Hugh