linux-kernel - Re: [PATCH][RFC] Simple tamper-proof device filesystem.

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Message-ID: <20080106074558.GA388@1wt.eu>
Date:	Sun, 6 Jan 2008 08:45:58 +0100
From:	Willy Tarreau <w@....eu>
To:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	serue@...ibm.com
Subject: Re: [PATCH][RFC] Simple tamper-proof device filesystem.

On Sun, Jan 06, 2008 at 04:36:06PM +0900, Tetsuo Handa wrote:
> Hello.
> 
> Willy Tarreau wrote:
> > Your patch is very confusing. In your description, as well as in the
> > comments you talk about tmpfs, but your patch does not touch even one
> > line of tmpfs and only changes ramfs. Even your variables and arguments
> > refer to tmpfs. The Kconfig entry indicates that the feature depends
> > on TMPFS too.
> > 
> > Judging from the following comment :
> >   * Original tmpfs doesn't set ramfs_dir_inode_operations.setattr field.
> > 
> > I suspect that you confuse both filesystems.
> >   - ramfs is in fs/ramfs and is always compiled in, you cannot disable it
> >   - tmpfs is in mm/shmem.c and is optional. It also supports options that
> >     ramfs does not (eg: size) and data may be swapped.
> > 
> > Please understand that I'm not discussing the usefulness of your patch,
> > I'm just trying to avoid a huge confusion.
> 
> Oh, I thought the filesystem mounted by "mount -t tmpfs none /tmp" is "tmpfs"

Yes, that is a tmpfs.

> and the source code of "tmpfs" is located in fs/ramfs directory.

No, ramfs is what you get by "mount -t ramfs none /tmp" :-)
You will notice that "df" will not report your ramfs by default because it
reports zero blocks. But "mount" or "df /tmp" will report it.

> So, I should write the description as "an extension to ramfs" rather than
> "an extension to tmpfs".

and please also the comments, macros and variable names in the code, as they
are what confused me first.

> I'll fix it in next posting.

Thanks,
Willy

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