linux-kernel - Re: new ...at() flag: AT_NO

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Message-ID: <20170501051506.GY29622@ZenIV.linux.org.uk>
Date:   Mon, 1 May 2017 06:15:06 +0100
From:   Al Viro <viro@...IV.linux.org.uk>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Matthew Wilcox <willy@...radead.org>,
        Linux API <linux-api@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Linux FS Devel <linux-fsdevel@...r.kernel.org>
Subject: Re: new ...at() flag: AT_NO_JUMPS

On Sun, Apr 30, 2017 at 09:52:37PM -0700, Andy Lutomirski wrote:
> On Sun, Apr 30, 2017 at 9:10 AM, Al Viro <viro@...iv.linux.org.uk> wrote:
> > On Sat, Apr 29, 2017 at 09:38:22PM -0700, Matthew Wilcox wrote:
> >
> >> It sounds more like AT_NO_ESCAPE ... or AT_BELOW, or something.
> >
> > I considered AT_ROACH_MOTEL at one point...  Another interesting
> > question is whether EXDEV would've been better than ELOOP.
> > Opinions?
> 
> In support of my homeland, I propose AT_HOTEL_CALIFORNIA.
> 
> How about EXDEV for crossing a mountpoint and ELOOP for absolute
> symlinks or invalid ..?  (Is there a technical reason why the same AT_
> flag should trigger both cases?)

You do realize that mount --bind can do everything absolute symlinks could,
right?  And absolute symlinks most likely do lead to (or at least through)
a different fs...