Re: [PATCH for-next v2] RDMA/rxe: Remove redundant page presence check

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

在 2025/6/8 11:59, Daisuke Matsuda 写道:
> hmm_pfn_to_page() does not return NULL. ib_umem_odp_map_dma_and_lock()
> should return an error in case the target pages cannot be mapped until
> timeout, so these checks can safely be removed.
> 
> Signed-off-by: Daisuke Matsuda <dskmtsd@gmail.com>
> ---
>   drivers/infiniband/sw/rxe/rxe_odp.c | 13 +------------
>   1 file changed, 1 insertion(+), 12 deletions(-)
> 
> diff --git a/drivers/infiniband/sw/rxe/rxe_odp.c b/drivers/infiniband/sw/rxe/rxe_odp.c
> index dbc5a5600eb7..02841346e30c 100644
> --- a/drivers/infiniband/sw/rxe/rxe_odp.c
> +++ b/drivers/infiniband/sw/rxe/rxe_odp.c
> @@ -203,8 +203,6 @@ static int __rxe_odp_mr_copy(struct rxe_mr *mr, u64 iova, void *addr,
>   
>   		page = hmm_pfn_to_page(umem_odp->map.pfn_list[idx]);
>   		user_va = kmap_local_page(page);
> -		if (!user_va)
> -			return -EFAULT;
>   
>   		src = (dir == RXE_TO_MR_OBJ) ? addr : user_va;
>   		dest = (dir == RXE_TO_MR_OBJ) ? user_va : addr;
> @@ -286,8 +284,6 @@ static enum resp_states rxe_odp_do_atomic_op(struct rxe_mr *mr, u64 iova,
>   	idx = rxe_odp_iova_to_index(umem_odp, iova);
>   	page_offset = rxe_odp_iova_to_page_offset(umem_odp, iova);
>   	page = hmm_pfn_to_page(umem_odp->map.pfn_list[idx]);

The function hmm_pfn_to_page will finally be "(mem_map + ((pfn) - 
ARCH_PFN_OFFSET))"

The procedure is as below:

hmm_pfn_to_page -- > pfn_to_page -- > __pfn_to_page -- > (mem_map + 
((pfn) - ARCH_PFN_OFFSET))

Thus, I am fine with it.

> -	if (!page)
> -		return RESPST_ERR_RKEY_VIOLATION;
>   
>   	if (unlikely(page_offset & 0x7)) {

Normally page_offset error handler should be after this line 
"page_offset = rxe_odp_iova_to_page_offset(umem_odp, iova);"

Why is this error handler after hmm_pfn_to_page?

>   		rxe_dbg_mr(mr, "iova not aligned\n");
> @@ -352,10 +348,6 @@ int rxe_odp_flush_pmem_iova(struct rxe_mr *mr, u64 iova,
>   		page_offset = rxe_odp_iova_to_page_offset(umem_odp, iova);
>   
>   		page = hmm_pfn_to_page(umem_odp->map.pfn_list[index]);
> -		if (!page) {
> -			mutex_unlock(&umem_odp->umem_mutex);
> -			return -EFAULT;
> -		}
>   
>   		bytes = min_t(unsigned int, length,
>   			      mr_page_size(mr) - page_offset);
> @@ -398,10 +390,7 @@ enum resp_states rxe_odp_do_atomic_write(struct rxe_mr *mr, u64 iova, u64 value)
>   	page_offset = rxe_odp_iova_to_page_offset(umem_odp, iova);
>   	index = rxe_odp_iova_to_index(umem_odp, iova);
>   	page = hmm_pfn_to_page(umem_odp->map.pfn_list[index]);
> -	if (!page) {
> -		mutex_unlock(&umem_odp->umem_mutex);
> -		return RESPST_ERR_RKEY_VIOLATION;
> -	}
> +
>   	/* See IBA A19.4.2 */
>   	if (unlikely(page_offset & 0x7)) {

Ditto, page_offset error handler is not after the line "page_offset = 
rxe_odp_iova_to_page_offset(umem_odp, iova);" ?

Thanks
Yanjun.Zhu

>   		mutex_unlock(&umem_odp->umem_mutex);