On Sun, 2014-03-02 at 10:22 +0800, Ian Kent wrote: > On Fri, 2014-02-28 at 08:29 -0500, Alexander Viro wrote: > > On Fri, Feb 28, 2014 at 01:12:58PM +0100, Donald Buczek wrote: > > > > > Obviously, "cleared mounted on dentry" is missing. > > > > > > It looks like we enter put_mountpoint() but don't get to > > > dentry->d_flags &= ~DCACHE_MOUNTED; > > > > > > mp->m_count is not zero probably. > > > > > > What does it mean? The mount is still locked but not in the mount hash? > > > > No, it means that something else is mounted on the same dentry (in another > > part of mount tree, obviously). > > > > If you mount the same fs on two different mountpoints, e.g. > > mount /dev/sda1 /mnt > > mount /dev/sda1 /tmp/foo > > you will have the same dentries seen in two places. Now, > > mount /dev/sdb11 /mnt/a > > mount /dev/sdc5 /tmp/foo/a > > > > and you've got two different filesystems mounted on two different places > > (/mnt/a and /tmp/foo/a). These two places have different vfsmounts, > > but the same dentry. struct mountpoint is associated with dentry, so > > it's also the same for both. And it serves as a mountpoint for two > > vfsmounts - one for fs from sdb11, another for fs from sdc5. > > > > Now umount /mnt/a; one of those two vfsmounts is gone now. struct mountpoint > > survives, of course, and dentry is *still* a mountpoint. sdc5 is still > > mounted on /tmp/foo/a, after all... Good example but for autofs file systems doesn't this amount to saying its been bound somewhere else? Illegal as far as autofs is concerned because an autofs mount is strictly associated with a path defined by its map. And, yes, bind mounting an autofs file system elsewhere isn't vetoed by the kernel. This makes be start thinking about implications wrt. containers .... > > Ahh, right ... I'll need to think about my use (misuse) of > d_mountpoint(). So maybe I don't need to worry about this just yet. > > Thanks Al. -- To unsubscribe from this list: send the line "unsubscribe autofs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
