On Tue, Jun 23, 2009 at 11:32:44AM +0100, Roger Leigh wrote:
> On Mon, Jun 22, 2009 at 09:17:18PM +0200, Karel Zak wrote:
> >
> > Hi Roger,
> >
> > On Sun, Jun 21, 2009 at 02:26:51PM +0100, Roger Leigh wrote:
> > > This information should be recorded in /proc/mounts now that this
> > > information can be passed to mount(2).
> >
> > really?
>
> Ah, it's missing some context from where the discussion originally
> started. This is referring to MS_BIND mountflags no longer being
> ignored.
I still think you are not right. The 2.6.26 kernel has introduced
/proc/self/mountinfo, but it seems that fs/namespace.c does not
export MS_BIND as a string option in /proc/mounts.
See (simple_mount.c code is below):
# ./simple_mount /mnt/test /mnt/test2 none 4096 rw,bind
# grep test /proc/mounts
/dev/root /mnt/test2 ext3 rw,noatime,relatime,errors=continue,user_xattr,acl,data=ordered 0 0
# grep test /proc/self/mountinfo
28 18 8:4 /mnt/test /mnt/test2 rw,noatime,relatime - ext3 /dev/root rw,errors=continue,user_xattr,acl,data=ordered
.. kernel 2.6.29.4-167.fc11.x86_64.
The most important problem with bind mounts in /proc/mounts is that
there is not information about the source directory (/mnt/test in my
example). There is source device only (e.g. /dev/root).
It means you can't call:
# mount --bind /source /target
# umount /source
on systems without mtab.
> This is WRT Debian bug reports
I'll check it later, thanks.
> > My plan is to support systems without /etc/mtab and use
> > /proc/self/mountinfo in util-linux-ng 2.{17,18} (September/October
> > 2009 or so...).
>
> Cool. Just to clarify: at this point, barring any unforseen bugs,
> we can delete /etc/mtab and running with just /proc will be a
> valid supported configuration?
Yes, mtab is Bad Thing.
> What will the minimum supported kernel version for such a configuration
> be (with mountinfo)?
kernel 2.6.26
> Will support for a writable mtab be removed at some future point?
at far far future...
Karel
#include <stdio.h>
#include <sys/mount.h>
int main(int argc, char *argv[]) {
unsigned long flags = 0;
char *data = NULL;
if (argc < 4) {
fprintf(stderr,
"usage %s <source> <target> <type> [<flags> [<data>]]\n",
argv[0]);
return 1;
}
if (argc >= 5)
flags = atoll(argv[4]);
if (argc == 6)
data = argv[5];
return mount (argv[1], argv[2], argv[3], flags, data);
}
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