Hello John, comments inline;

On Fri, 2020-02-07 at 14:54 -0800, John Hubbard wrote:

On 2/5/20 7:25 PM, Leonardo Bras wrote:

quoted

On Thu, 2020-02-06 at 00:08 -0300, Leonardo Bras wrote:

quoted

                gup_pgd_range(addr, end, gup_flags, pages, &nr);
-               local_irq_enable();
+               end_lockless_pgtbl_walk(IRQS_ENABLED);
                ret = nr;
        }
 

Just noticed IRQS_ENABLED is not available on other archs than ppc64.
I will fix this for v7.

What's the fix going to look like, approximately?

I am not sure what is the best approach yet. 

1. On irq_mask == 0, always enable irq on end_lockless_pgtbl_walk().
   Not sure how bat would that affect other archs.

2. Add another function like end_lockless_pgtbl_walk_irqen() that
always enables IRQ.

3. Add another parameter in end_lockless_pgtbl_walk(), so that caller
can choose ii IRQ must be enabled.

Also, not sure if internal_get_user_pages_fast() can possibly be called
with IRQ disabled, and then return with it enabled. Maybe just
saving/restoring should be fine.

Other suggestions are welcome.

thanks,

Best regards,

Leonardo Bras