[patch] nmount ro, rw and negated option handling

[Jaakko Heinonen]

On 2011-01-19, Craig Rodrigues wrote:
> I disagree with your patch and do not approve it.
> 
> I prefer something simpler:

Thanks for your reply. However, your patch doesn't fix the bug(s) I
tried to resolve. See below.

> ZFS can be changed to check for "rw" or "noro".

It's possible but I don't like to support both "rw" and "noro". That
makes the file system code unnecessary prone for bugs when someone
forgets to test for both options.
 
> > 1. Have mountd(8) running.
> > 2. # mdconfig -a -t vnode -f ufsimg
> > 3. # mount -o ro,rw /dev/md0 /mnt

With your patch[1] after the third step the mount point has both "ro"
and and "noro" active but the MNT_RDONLY flag is not set. Again, you
will eventually get the  "ffs_sync: rofs mod" (or similar) panic because
the "ro" option is active during remount.

Also, I didn't verify but I doubt that your patch will fix the problem
described in PR kern/150206.

[1] I had to comment vfs_mount.c line 622 "has_noro = 1;" and remove
    the noro_opt declaration to be able to compile kernel with your
    patch applied.

-- 
Jaakko