Re: RO --bind mount implementation ...

From: Herbert Pötzl (herbert@13thfloor.at)
Date: Tue Aug 05 2003 - 18:14:49 EST


On Wed, Aug 06, 2003 at 12:51:49AM +0200, Herbert Pötzl wrote:
> On Tue, Aug 05, 2003 at 05:59:24PM +0100, viro@parcelfarce.linux.theplanet.co.uk wrote:
> > On Tue, Aug 05, 2003 at 12:16:15AM +0200, Herbert Pötzl wrote:
> >
> > > anyway, I discussed this with some friends, and
> > > they pointed out that this would be useful ...
> > > so here is the first try ...
> >
> > Umm... You know, the most obvious system call that should care about
> > read-only is open(pathname, O_RDWR) ;-) IOW, taking care of directory
> > modifications is not enough - you need to deal with
> > * opening file for write
> > * truncation (both from *truncate() and from open() with O_TRUNC)
> > * metadata changes (timestamps, ownership, permissions)
>
> well, the open case, IMHO is handled by the
> lookup_create() modifications, truncate is something

more descriptive would have been:
- I guess this is handled in open_namei() by

     error = -EROFS;
     if ((flag & 2) && (IS_RDONLY(inode) || MNT_IS_RDONLY(nd->mnt)))
            goto exit;

> best,
> Herbert
-
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