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From: Andy Lutomirski <luto@amacapital.net>
Date: Fri, 15 Jan 2016 08:31:25 -0800
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Subject: Re: [PATCH] fuse: Add support for fuse stacked I/O
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: fuse-devel <fuse-devel@lists.sourceforge.net>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Greg KH <gregkh@linuxfoundation.org>,
        Nikhilesh Reddy <reddyn@codeaurora.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Nikolaus Rath <nikolaus@rath.org>,
        Linux API <linux-api@vger.kernel.org>, Jan Kara <jack@suse.cz>,
        "Theodore Ts'o" <tytso@mit.edu>, sven.utcke@gmx.de,
        Antonio SJ Musumeci <trapexit@spawn.link>,
        Miklos Szeredi <miklos@szeredi.hu>,
        Richard Weinberger <richard@nod.at>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Jan 14, 2016 11:19 AM, "Linus Torvalds"
<torvalds@linux-foundation.org> wrote:
>
> On Thu, Jan 14, 2016 at 10:57 AM, Nikhilesh Reddy <reddyn@codeaurora.org> wrote:
> >
> > *I will send out a properly formatted patch shortly.*
>
> So before you do that, can you explain in what cases fuse just wants
> to pass through the IO?
>
> Why aren't such cases just using unionfs or something?
>
> In other words, I think that patch needs an explanation for the
> *reason* for the new functionality.

Also, clarifying the functionality would be nice.  What is the
"underlying" fs you speak of?  What f_cred gets used?  Who opens the
underlying file, whatever that is?

Is the intent overlay-style stacking or is it something else entirely?

--Andy