Re: [PATCH 6/6] gfs2: Fix mmap + page fault deadlocks (part 2)

[Jan Kara <jack@suse.cz>]

On Fri 21-05-21 17:46:04, Andreas Gruenbacher wrote:
> On Fri, May 21, 2021 at 5:23 PM Jan Kara <jack@suse.cz> wrote:
> > On Thu 20-05-21 16:07:56, Andreas Gruenbacher wrote:
> > > > So you probably need to add a new VM_FAULT_
> > > > return code that will behave like VM_FAULT_SIGBUS except it will not raise
> > > > the signal.
> > >
> > > A new VM_FAULT_* flag might make the code easier to read, but I don't
> > > know if we can have one.
> >
> > Well, this is kernel-internal API and there's still plenty of space in
> > vm_fault_reason.
> 
> That's in the context of the page fault. The other issue is how to
> propagate that out through iov_iter_fault_in_readable ->
> fault_in_pages_readable -> __get_user, for example. I don't think
> there's much of a chance to get an additional error code out of
> __get_user and __put_user.

Yes, at that level we'd get EFAULT as in any other case. Really the only
difference of the new VM_FAULT_ error code from a case of "standard" error
and VM_FAULT_SIGBUS would be not raising the signal.

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR