Date: Mon, 5 Sep 2005 10:27:35 +0200
From: Pavel Machek <pavel@ucw.cz>
To: "Theodore Ts'o" <tytso@mit.edu>, David Teigland <teigland@redhat.com>,
       Andrew Morton <akpm@osdl.org>, Alan Cox <alan@lxorguk.ukuu.org.uk>,
       linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
       linux-cluster@redhat.com
Subject: real read-only [was Re: GFS, what's remaining]
Message-ID: <20050905082735.GA2662@elf.ucw.cz>
References: <20050901104620.GA22482@redhat.com> <20050901035939.435768f3.akpm@osdl.org> <1125586158.15768.42.camel@localhost.localdomain> <20050901132104.2d643ccd.akpm@osdl.org> <20050903051841.GA13211@redhat.com> <20050904203344.GA1987@elf.ucw.cz> <20050905055428.GA29158@thunk.org>
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Hi!

> > > - read-only mount
> > > - "specatator" mount (like ro but no journal allocated for the mount,
> > >   no fencing needed for failed node that was mounted as specatator)
> > 
> > I'd call it "real-read-only", and yes, that's very usefull
> > mount. Could we get it for ext3, too?
> 
> This is a bit of a degression, but it's quite a bit different from
> what ocfs2 is doing, where it is not necessary to replay the journal
> in order to assure filesystem consistency.  
> 
> In the ext3 case, the only time when read-only isn't quite read-only
> is when the filesystem was unmounted uncleanly and the journal needs
> to be replayed in order for the filesystem to be consistent.

Yes, I know... And that is going to be a disaster when you are
attempting to recover data from failing harddrive (and absolutely do
not want to write there).

There's a better reason, too. I do swsusp. Then I'd like to boot with
/ mounted read-only (so that I can read my config files, some
binaries, and maybe suspended image), but I absolutely may not write
to disk at this point, because I still want to resume.

Currently distros do that using initrd, but that does not allow you to
store suspended image into file, and is slightly hard to setup.

								Pavel
-- 
if you have sharp zaurus hardware you don't need... you know my address
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