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From: David Howells <dhowells@redhat.com>
To: Miklos Szeredi <mszeredi@redhat.com>
Cc: dhowells@redhat.com, viro <viro@zeniv.linux.org.uk>,
	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>
Subject: Re: User-visible context-mount API
Date: Tue, 16 Jan 2018 14:18:22 +0000	[thread overview]
Message-ID: <30249.1516112302@warthog.procyon.org.uk> (raw)
In-Reply-To: <CAOssrKc46bf=yme=zSubYF6t-TGfxEpCaKMQ6GVp30-vuaXWLw@mail.gmail.com>

Miklos Szeredi <mszeredi@redhat.com> wrote:

> > Maybe - the problem is that it's harder to manage if you've got multiple
> > mounts attached to a single superblock as you can only change the superblock
> > state if all the mounts are R/O.
> 
> Not true:
> 
>  [root@veci ~]# cat /proc/self/mountinfo | grep 46
> 212 78 0:46 / /tmp/1 rw,relatime shared:153 - tmpfs tmpfs rw,seclabel
> 219 78 0:46 / /tmp/2 rw,relatime shared:153 - tmpfs tmpfs rw,seclabel
> [root@veci ~]# mount -oremount,ro /tmp/1
> [root@veci ~]# cat /proc/self/mountinfo | grep 46
> 212 78 0:46 / /tmp/1 ro,relatime shared:153 - tmpfs tmpfs ro,seclabel
> 219 78 0:46 / /tmp/2 rw,relatime shared:153 - tmpfs tmpfs ro,seclabel
> [root@veci ~]# mount -oremount,bind,rw /tmp/1
> [root@veci ~]# cat /proc/self/mountinfo | grep 46
> 212 78 0:46 / /tmp/1 rw,relatime shared:153 - tmpfs tmpfs ro,seclabel
> 219 78 0:46 / /tmp/2 rw,relatime shared:153 - tmpfs tmpfs ro,seclabel
> [root@veci ~]#
> 
> R/O flag on mount and on superblock can be changed independently.

Ah...  I misread the code.  I was looking at the check that there are no
writers on a mount.

David

  parent reply	other threads:[~2018-01-16 14:18 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 [this message]
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
2018-01-19  6:32         ` Al Viro

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