Hello David, Miklos,
I've been looking at the new mount API (fsopen(), fsconfig(),
fsmount(), move_mount(), etc.) and among the details that remain
mysterious to me is this: how does one set the propagation type
(private/shared/slave/unbindable) of a new mount and change the
propagation type of an existing mount?
I've looked at the kernel source for a bit, and did not see how this
is possible.
The draft manual pages sent out a few months ago provide little clue,
with the only hint being in the draft fsopen(2) page, which says of
fsmount():
fsmount() takes the file descriptor returned by fsopen() and cre‐
ates a mount object for the filesystem root specified there. The
attributes of the mount object are set from the mount_attrs param‐
eter. The attributes specify the propagation and mount restric‐
tions to be applied to accesses through this mount.
However, that text appears *not* to be true. The 'mount_attrs'
argument of fsmount() does not seem to permit specification of
propagation type, since in the kernel there is this check:
if (attr_flags & ~(MOUNT_ATTR_RDONLY |
MOUNT_ATTR_NOSUID |
MOUNT_ATTR_NODEV |
MOUNT_ATTR_NOEXEC |
MOUNT_ATTR__ATIME |
MOUNT_ATTR_NODIRATIME))
return -EINVAL;
Thanks,
Michael
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
