Re: [PATCH v34 10/24] mm: Add vm_ops->mprotect()

[Jarkko Sakkinen]

On Tue, Jul 07, 2020 at 04:24:08AM +0100, Matthew Wilcox wrote:
> On Mon, Jul 06, 2020 at 08:22:54PM -0700, Sean Christopherson wrote:
> > On Tue, Jul 07, 2020 at 04:14:24AM +0100, Matthew Wilcox wrote:
> > > > +		if (vma->vm_ops && vma->vm_ops->mprotect) {
> > > > +			error = vma->vm_ops->mprotect(vma, nstart, tmp, prot);
> > > > +			if (error)
> > > > +				goto out;
> > > > +		}
> > 
> > Based on "... and then the vma owner can do whatever it needs to before
> > calling mprotect_fixup(), which is already not static", my interpretation
> > is that Matthew's intent was to do:
> > 
> > 		if (vma->vm_ops && vma->vm_ops->mprotect)
> > 			error =  = vma->vm_ops->mprotect(vma, nstart, tmp, prot);
> > 		else
> > 			error = mprotect_fixup(vma, &prev, nstart, tmp, newflags);
> > 		if (error)
> > 			goto out;
> > 
> > i.e. make .mprotect() a full replacement as opposed to a prereq hook.
> 
> Yes, it was.  I was just looking at the next patch to be sure this was
> how I'd been misunderstood.

I'm don't get this part. If mprotect_fixup is called in the tail of the
callback, why it has to be called inside the callback and not be called
after the callback?

The reason I only part did what you requested was to do only the part of
the change that I get. Not to oppose it.

/Jarkko