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From: Al Viro <viro@ZenIV.linux.org.uk>
To: Karel Zak <kzak@redhat.com>
Cc: Miklos Szeredi <mszeredi@redhat.com>,
	David Howells <dhowells@redhat.com>,
	Jeff Layton <jlayton@redhat.com>,
	"Eric W. Biederman" <ebiederm@redhat.com>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Linux API <linux-api@vger.kernel.org>,
	util-linux@vger.kernel.org,
	"Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
Subject: Re: User-visible context-mount API
Date: Fri, 19 Jan 2018 02:27:18 +0000	[thread overview]
Message-ID: <20180119022717.GF13338@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20180117110633.zneqvnjzgxkv4yc2@ws.net.home>

On Wed, Jan 17, 2018 at 12:06:33PM +0100, Karel Zak wrote:

> What about new flag (for the API) rather than try to be smart with the
> current flags? But I have doubts that invest time to new mount(2)
> features is a good idea.

Would be nice, if we had any spare bits left...  We could, in principle,
turn
#define MS_BIND         4096
#define MS_MOVE         8192
into
#define MS_BIND         0x1000
#define MS_MOVE         0x2000
#define MS_SOMETHING    0x3000
seeing that they should never be used together, but... mount(2)
doesn't reject MS_BIND|MS_MOVE and treats it as MS_BIND instead.
_Probably_ nothing would care, but it risks breaking userland.

We could use one of the internal-only bits for that instead, but
they are also quietly ignored and not rejected, so that would
have the same problem.

mount(2) ABI sucks, film at 11...

  parent reply	other threads:[~2018-01-19  2:27 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-15 16:07 David Howells
2018-01-15 17:31 ` Eric W. Biederman
2018-01-15 17:32 ` Eric W. Biederman
2018-01-16  9:01 ` Miklos Szeredi
2018-01-16 10:10 ` David Howells
2018-01-16 10:35   ` Miklos Szeredi
2018-01-16 14:18   ` David Howells
2018-01-17 10:43   ` Karel Zak
2018-01-16 14:55 ` David Howells
2018-01-16 15:40 ` David Howells
2018-01-16 16:41   ` Miklos Szeredi
2018-01-17  4:17     ` Al Viro
2018-01-17  9:53       ` Miklos Szeredi
2018-01-17 11:06         ` Karel Zak
2018-01-18  9:48           ` Miklos Szeredi
2018-01-19  2:27           ` Al Viro [this message]
2018-01-19  6:32         ` Al Viro

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