Re: [PATCH] mm: vmalloc: annotate find_vmap_area_exceed_addr_lock() for lockdep

[Jens Axboe <axboe@kernel.dk>]

On 3/27/24 11:04 AM, Uladzislau Rezki wrote:
> Hello, Jens, Omar!
> 
>> On Tue, Mar 26, 2024 at 04:24:01PM -0600, Jens Axboe wrote:
>>> On 3/26/24 3:25 PM, Jens Axboe wrote:
>>>> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
>>>> index 22aa63f4ef63..26a69fa6809c 100644
>>>> --- a/mm/vmalloc.c
>>>> +++ b/mm/vmalloc.c
>>>> @@ -1032,7 +1032,7 @@ find_vmap_area_exceed_addr_lock(unsigned long addr, struct vmap_area **va)
>>>>  	for (i = 0; i < nr_vmap_nodes; i++) {
>>>>  		vn = &vmap_nodes[i];
>>>>  
>>>> -		spin_lock(&vn->busy.lock);
>>>> +		spin_lock_nested(&vn->busy.lock, i);
>>>>  		va_lowest = __find_vmap_area_exceed_addr(addr, &vn->busy.root);
>>>>  		if (va_lowest) {
>>>>  			if (!va_node || va_lowest->va_start < (*va)->va_start) {
>>>
>>> Omar said he tested this and ran into lockdep complaining as it only
>>> supports 8 subclasses. So this patch can't work, but that still leaves
>>> the current kernel code buggy...
>>> 	
>> It is a bit tricky. Let me rewrite it so a lockdep does not complain.
>>
>> Thank you for your report.
>>
> 
> Could you please check and test below? It is based on latest 6.9-rc1 tip.
> I have reworked it a bit and now it does not hold two locks so the lockdep
> should not complain.

Works for me:

Tested-by: Jens Axboe <axboe@kernel.dk>

-- 
Jens Axboe