Re: [PATCH] RDMA/siw: use kzalloc_flex

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

Hi Rosen, all,

thanks for your patch. As stated, I think we shall make a change
to it, which exchanges 'num_pages' with more appropriate
'num_chunks' logic. Since I haven't received a response to my
first reply yet, I'll send an RFC patch right away. I'll
restrict it to linux-rdma list and other individuals on cc
in your patch.

Thanks,
Bernard.

On 29.03.2026 15:21, Bernard Metzler wrote:
> 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))
>