On Tue, Aug 30, 2016 at 03:01:51PM -0700, Andy Lutomirski wrote:
> On Wed, Aug 24, 2016 at 9:51 AM, Josh Cartwright <jo...@ni.com> wrote:
[..]
> >> diff --git a/kernel/fork.c b/kernel/fork.c
> >> index 52e725d4a866..05f7ef796fb4 100644
> >> --- a/kernel/fork.c
> >> +++ b/kernel/fork.c
> >> @@ -158,19 +158,39 @@ void __weak arch_release_thread_stack(unsigned long
> >> *stack)
> >> * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
> >> * kmemcache based allocator.
> >> */
> >> -# if THREAD_SIZE >= PAGE_SIZE
> >> -static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
> >> - int node)
> >> +# if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
> >> +static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
> >> int node)
> >> {
> >> +#ifdef CONFIG_VMAP_STACK
> >> + void *stack = __vmalloc_node_range(THREAD_SIZE, THREAD_SIZE,
> >> + VMALLOC_START, VMALLOC_END,
> >> + THREADINFO_GFP | __GFP_HIGHMEM,
> >> + PAGE_KERNEL,
> >> + 0, node,
> >> + __builtin_return_address(0));
> >> +
> >> + /*
> >> + * We can't call find_vm_area() in interrupt context, and
> >> + * free_thread_stack can be called in interrupt context, so cache
> >> + * the vm_struct.
> >> + */
> >> + if (stack)
> >> + tsk->stack_vm_area = find_vm_area(stack);
> >
> > This is annoying, we end up having to walk the vm_area tree twice (once
> > for the allocation, then here to get a handle on area).
> >
> > Perhaps it's time the vmalloc code learned an allocation API that
> > returned the vm_area handle as well.
>
> Agreed. I may do this once everything else lands.
There are at least a few other places that could benefit from this,
doing a quick scan of find_vm_area() callers: vmalloc_{32_,}_user() and
kasan_module_alloc().
Josh
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