Re: [PATCH] RDMA/siw: use kzalloc_flex

[Bernard Metzler <bernard.metzler@linux.dev>]

On 27.03.2026 04:00, Rosen Penev wrote:
> Simplifies allocations by using a flexible array member in this struct.
> 
> Add __counted_by to get extra runtime analysis.
> 
> Signed-off-by: Rosen Penev <rosenp@gmail.com>
> ---
>   drivers/infiniband/sw/siw/siw.h     |  2 +-
>   drivers/infiniband/sw/siw/siw_mem.c | 12 +++---------
>   2 files changed, 4 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/infiniband/sw/siw/siw.h b/drivers/infiniband/sw/siw/siw.h
> index f5fd71717b80..2b327a899a1c 100644
> --- a/drivers/infiniband/sw/siw/siw.h
> +++ b/drivers/infiniband/sw/siw/siw.h
> @@ -119,9 +119,9 @@ struct siw_page_chunk {
>   
>   struct siw_umem {
>   	struct ib_umem *base_mem;
> -	struct siw_page_chunk *page_chunk;
>   	int num_pages;

Shouldn't we replace 'num_pages' by a 'num_chunks' and change
memory allocation and release code accordingly?

>   	u64 fp_addr; /* First page base address */
> +	struct siw_page_chunk page_chunk[] __counted_by(num_pages);
>   };
>   
>   struct siw_pble {
> diff --git a/drivers/infiniband/sw/siw/siw_mem.c b/drivers/infiniband/sw/siw/siw_mem.c
> index 98c802b3ed72..08047fcf0df1 100644
> --- a/drivers/infiniband/sw/siw/siw_mem.c
> +++ b/drivers/infiniband/sw/siw/siw_mem.c
> @@ -50,7 +50,6 @@ void siw_umem_release(struct siw_umem *umem)
>   		kfree(umem->page_chunk[i].plist);
>   		num_pages -= PAGES_PER_CHUNK;
>   	}
> -	kfree(umem->page_chunk);
>   	kfree(umem);
>   }
>   
> @@ -347,16 +346,12 @@ struct siw_umem *siw_umem_get(struct ib_device *base_dev, u64 start,
>   	num_pages = PAGE_ALIGN(start + len - first_page_va) >> PAGE_SHIFT;
>   	num_chunks = (num_pages >> CHUNK_SHIFT) + 1;
>   
> -	umem = kzalloc_obj(*umem);
> +	umem = kzalloc_flex(*umem, page_chunk, num_chunks);
>   	if (!umem)
>   		return ERR_PTR(-ENOMEM);
>   
> -	umem->page_chunk =
> -		kzalloc_objs(struct siw_page_chunk, num_chunks);
> -	if (!umem->page_chunk) {
> -		rv = -ENOMEM;
> -		goto err_out;
> -	}
> +	umem->num_pages = num_pages;
> +
>   	base_mem = ib_umem_get(base_dev, start, len, rights);
>   	if (IS_ERR(base_mem)) {
>   		rv = PTR_ERR(base_mem);
> @@ -385,7 +380,6 @@ struct siw_umem *siw_umem_get(struct ib_device *base_dev, u64 start,
>   		umem->page_chunk[i].plist = plist;
>   		while (nents--) {
>   			*plist = sg_page_iter_page(&sg_iter);
> -			umem->num_pages++;
>   			num_pages--;
>   			plist++;
>   			if (!__sg_page_iter_next(&sg_iter))