On Fri, Jun 11, 2021 at 04:25:10PM +, Al Viro wrote:
> On Wed, Jun 02, 2021 at 01:16:32PM +0200, Andreas Gruenbacher wrote:
>
> > Well, iomap_file_buffered_write() does that by using
> > iov_iter_fault_in_readable() and iov_iter_copy_from_user_atomic() as
> > in iomap_write_actor(), but the re
On Mon, May 31, 2021 at 05:12:31PM +, Al Viro wrote:
> > +int iov_iter_fault_in_writeable(struct iov_iter *i, size_t bytes)
> > +{
> > + size_t skip = i->iov_offset;
> > + const struct iovec *iov;
> > + int err;
> > + struct iovec v;
> > +
> > + if (!(i->type & (ITER_BVEC|ITER_KVEC))
On Sat, Jun 12, 2021 at 09:05:40PM +, Al Viro wrote:
> Is the above an accurate description of the mainline situation there?
> In particular, normal read doesn't seem to bother with locks at all.
> What exactly are those cluster locks for in O_DIRECT read?
BTW, assuming the lack of contention
On Sat, Jun 12, 2021 at 2:12 PM Al Viro wrote:
>
> Actually, is there any good way to make sure that write fault is triggered
> _without_ modification of the data? On x86 lock xadd (of 0, that is) would
> probably do it and some of the other architectures could probably get away
> with using cmpx
On Sat, Jun 12, 2021 at 02:33:31PM -0700, Linus Torvalds wrote:
> That said, reads are obviously much easier, and I'd probably prefer
> the model for writes to be to not necessarily pre-fault anything at
> all, but just write to user space with page faults disabled.
*nod*
I don't like that write
On Sat, Jun 12, 2021 at 2:47 PM Al Viro wrote:
>
> O_DIRECT case is a PITA - there we use GUP and there's no way
> to tell GUP that in the current situation we do *NOT* want to hit
> ->fault()/->page_mkwrite()/etc. pagefault_disable() won't be even
> noticed there...
Well, we could chang
On Sat, Jun 12, 2021 at 04:17:30PM -0700, Linus Torvalds wrote:
> On Sat, Jun 12, 2021 at 2:47 PM Al Viro wrote:
> >
> > O_DIRECT case is a PITA - there we use GUP and there's no way
> > to tell GUP that in the current situation we do *NOT* want to hit
> > ->fault()/->page_mkwrite()/etc.
