Re: [PATCH rdma-next 5/6] RDMA/mlx5: Change check for cacheable user mkeys

[Zhu Yanjun <yanjun.zhu@linux.dev>]

在 2024/1/26 4:02, Leon Romanovsky 写道:
> On Thu, Jan 25, 2024 at 09:38:24AM -0400, Jason Gunthorpe wrote:
>> On Thu, Jan 25, 2024 at 08:52:57PM +0800, Junxian Huang wrote:
>>>
>>>
>>> On 2024/1/25 20:30, Leon Romanovsky wrote:
>>>> From: Or Har-Toov <ohartoov@nvidia.com>
>>>>
>>>> In the dereg flow, UMEM is not a good enough indication whether an MR
>>>> is from userspace since in mlx5_ib_rereg_user_mr there are some cases
>>>> when a new MR is created and the UMEM of the old MR is set to NULL.
>>>> Currently when mlx5_ib_dereg_mr is called on the old MR, UMEM is NULL
>>>> but cache_ent can be different than NULL. So, the mkey will not be
>>>> destroyed.
>>>> Therefore checking if mkey is from user application and cacheable
>>>> should be done by checking if rb_key or cache_ent exist and all other kind of
>>>> mkeys should be destroyed.
>>>>
>>>> Fixes: dd1b913fb0d0 ("RDMA/mlx5: Cache all user cacheable mkeys on dereg MR flow")
>>>> Signed-off-by: Or Har-Toov <ohartoov@nvidia.com>
>>>> Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
>>>> ---
>>>>   drivers/infiniband/hw/mlx5/mr.c | 15 ++++++++-------
>>>>   1 file changed, 8 insertions(+), 7 deletions(-)
>>>>
>>>> diff --git a/drivers/infiniband/hw/mlx5/mr.c b/drivers/infiniband/hw/mlx5/mr.c
>>>> index 12bca6ca4760..3c241898e064 100644
>>>> --- a/drivers/infiniband/hw/mlx5/mr.c
>>>> +++ b/drivers/infiniband/hw/mlx5/mr.c
>>>> @@ -1857,6 +1857,11 @@ static int cache_ent_find_and_store(struct mlx5_ib_dev *dev,
>>>>   	return ret;
>>>>   }
>>>>   
>>>> +static bool is_cacheable_mkey(struct mlx5_ib_mkey mkey)
>>>
>>> I think it's better using a pointer as the parameter instead of the struct itself.
>>
>> Indeed, that looks like a typo
> 
> It is suboptimal to pass struct by value, because whole struct will be copied,

Agree. With a pointer, an address is passed. With the struct, the whole 
struct is copied and passed. The overhead of calling function is less 
with a pointer.

Zhu Yanjun

> but it is not a mistake too.
> 
> Thanks
> 
>>
>> Thanks,
>> Jason
>>