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

[Mathieu Desnoyers]

----- On Oct 16, 2018, at 8:27 PM, Sergey Senozhatsky sergey.senozhatsky.work@xxxxxxxxx wrote:

> 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().

Good point, will do!

So I'll do one cleanup patch for vm_unmap_ram(), and I'll modify the new vm_unmap_user_ram().

Thanks,

Mathieu

> 
> 	-ss

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com