Re: [RFC PATCH for 4.21 04/16] mm: Introduce vm_map_user_ram, vm_unmap_user_ram

[Sergey Senozhatsky]

On (10/16/18 14:30), Steven Rostedt wrote:
> > +void vm_unmap_user_ram(const void *mem, unsigned int count)
> > +{
> > +	unsigned long size = (unsigned long)count << PAGE_SHIFT;
> > +	unsigned long addr = (unsigned long)mem;
> > +	struct vmap_area *va;
> > +
> > +	might_sleep();
> > +	BUG_ON(!addr);
> > +	BUG_ON(addr < VMALLOC_START);
> > +	BUG_ON(addr > VMALLOC_END);
> > +	BUG_ON(!PAGE_ALIGNED(addr));
> > +
> > +	debug_check_no_locks_freed(mem, size);
> > +	va = find_vmap_area(addr);
> > +	BUG_ON(!va);
> > +	free_unmap_vmap_area(va);
> > +}
> > +EXPORT_SYMBOL(vm_unmap_user_ram);
> > +
> 
> Noticing this from Sergey's question in another patch, why are you
> using BUG_ON()? That's rather extreme and something we are trying to
> avoid adding more of (I still need to remove the BUG_ON()s I've added
> over ten years ago). I don't see why all these BUG_ON's can't be turned
> into:

+1

> 	if (WARN_ON(x))
> 		return;

Given that this somewhat MM-related, I'd may be say VM_WARN_ON().

	-ss