Re: BUG: Mount ignores mount options

From: Al Viro
Date: Fri Aug 10 2018 - 22:17:27 EST

On Sat, Aug 11, 2018 at 02:58:15AM +0100, Al Viro wrote:
> On Fri, Aug 10, 2018 at 08:05:44PM -0500, Eric W. Biederman wrote:
> > All I proposed was that we distinguish between a first mount and an
> > additional mount so that userspace knows the options will be ignored.
> For pity sake, just what does it take to explain to you that your
> notions of "first mount" and "additional mount" ARE HEAVILY FS-DEPENDENT
> and may depend upon the pieces of state userland (especially in container)
> simply does not have?
> One more time, slowly:
> mount -t nfs4 /mnt/a
> mount -t nfs4 /mnt/b
> yield the same superblock. Is anyone who mounts something over NFS
> required to know if anybody else has mounted something from the same
> server, and if so how the hell are they supposed to find that out,
> so that they could decide whether they are creating the "first" or
> "additional" mount, whatever that might mean in this situation?
> And how, kernel-side, is that supposed to be handled by generic code
> of any description?
> While we are at it,
> mount -t nfs4 -o wsize=16384 /mnt/c
> is *NOT* the same superblock as the previous two.

s/as the previous two/as in the previous two cases/, that is - the first two
examples yield one superblock, this one - another.