Re: FMODE_EXEC or alike?

[Antonio Vargas]

On 2/21/06, Trond Myklebust <trond.myklebust@xxxxxxxxxx> wrote:
> On Mon, 2006-02-20 at 21:51 -0800, Andrew Morton wrote:
> > Oleg Drokin <green@xxxxxxxxxxxxxx> wrote:
> > >
> > > Hello!
> > >
> > >    We are working on a lustre client that would not require any patches
> > >    to linux kernel. And there are few things that would be nice to have
> > >    that I'd like your input on.
> > >
> > >    One of those is FMODE_EXEC - to correctly detect cross-node situations with
> > >    executing a file that is opened for write or the other way around, we need
> > >    something like this extra file mode to be present (and used as a file open
> > >    mode when opening files for exection, e.g. in fs/exec.c)
> > >    Do you think there is a chance this can be included into vanilla kernel,
> > >    or is there a better solution I oversee?
> > >    I am just thinking about something as simple as this
> > >    (with some suitable FMODE_EXEC define, of course):
> > >
> > > --- linux/fs/exec.c.orig    2006-02-21 00:11:47.000000000 +0200
> > > +++ linux/fs/exec.c 2006-02-21 00:12:24.000000000 +0200
> > > @@ -127,7 +127,7 @@ asmlinkage long sys_uselib(const char __
> > >     struct nameidata nd;
> > >     int error;
> > >
> > > -   error = __user_path_lookup_open(library, LOOKUP_FOLLOW, &nd, FMODE_READ);
> > > +   error = __user_path_lookup_open(library, LOOKUP_FOLLOW, &nd, FMODE_READ|FMODE_EXEC);
> > >     if (error)
> > >             goto out;
> > >
> > > @@ -477,7 +477,7 @@ struct file *open_exec(const char *name)
> > >     int err;
> > >     struct file *file;
> > >
> > > -   err = path_lookup_open(name, LOOKUP_FOLLOW, &nd, FMODE_READ);
> > > +   err = path_lookup_open(name, LOOKUP_FOLLOW, &nd, FMODE_READ|FMODE_EXEC);
> > >     file = ERR_PTR(err);
> > >
> > >     if (!err) {
> > >
> >
> > Such a patch would have zero runtime cost.  I'd have no problem carrying
> > that if it makes things easier for lustre, personally.
> >
> > We would need to understand whether this is needed by other distributed
> > filesystems and if so, whether the proposed implementation is suitable and
> > sufficient.
>
> Hmm.... We might possibly want to use that for NFSv4 at some point in
> order to deny write access to the file to other clients while it is in
> use.

When done with regards to failing a write if anyone has mapped the
file for executing it, or failing the execute if it's open/mmaped for
write, I can't really see the difference between local, remote and
clustered filesystems...

--
Greetz, Antonio Vargas aka winden of network

http://wind.codepixel.com/
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