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From: Al Viro <viro-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
To: Karel Zak <kzak-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: Miklos Szeredi <mszeredi-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	David Howells <dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Jeff Layton <jlayton-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	"Eric W. Biederman"
	<ebiederm-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	linux-fsdevel
	<linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	Linux API <linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	util-linux-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	"Michael Kerrisk (man-pages)"
	<mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
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-xkT7n84Rsxv/9pzu0YdTqQ@public.gmane.org>

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

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <28167.1516032442@warthog.procyon.org.uk>
     [not found] ` <28167.1516032442-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
2018-01-16  9:01   ` User-visible context-mount API Miklos Szeredi
2018-01-16 10:10 ` David Howells
2018-01-16 10:35   ` Miklos Szeredi
     [not found]   ` <CAOssrKc46bf=yme=zSubYF6t-TGfxEpCaKMQ6GVp30-vuaXWLw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-01-16 14:18     ` David Howells
     [not found]   ` <22576.1516097412-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
2018-01-17 10:43     ` Karel Zak
     [not found] ` <CAOssrKdgudK7kKbhQBAnV9EwzHBq=4+9M26JGfmhNDGrGXmnFg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-01-16 15:40   ` David Howells
     [not found]     ` <1643.1516117204-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
2018-01-16 16:41       ` Miklos Szeredi
     [not found]         ` <CAOssrKdn-ZhOB9V28uL-JK9zgNGJzF4cFBeyoqLLj4pADqNFVQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-01-17  4:17           ` Al Viro
2018-01-17  9:53             ` Miklos Szeredi
     [not found]               ` <CAOssrKfN_ZT5yJC1mxkhUf6FG=_eMD4nzQtETfu_4X3vOf1kHw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-01-17 11:06                 ` Karel Zak
     [not found]                   ` <20180117110633.zneqvnjzgxkv4yc2-xkT7n84Rsxv/9pzu0YdTqQ@public.gmane.org>
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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