Re: [Intel-gfx] [PATCH rdma-next v4 4/4] RDMA/umem: Move to allocate SG table from pages

Maor Gottlieb
2020-09-30T12:48:37Z

On 9/30/2020 2:45 PM, Jason Gunthorpe wrote:
> On Wed, Sep 30, 2020 at 12:53:21PM +0300, Leon Romanovsky wrote:
>> On Tue, Sep 29, 2020 at 04:59:29PM -0300, Jason Gunthorpe wrote:
>>> On Sun, Sep 27, 2020 at 09:46:47AM +0300, Leon Romanovsky wrote:
>>>> @@ -296,11 +223,17 @@ static struct ib_umem *__ib_umem_get(struct ib_device *device,
>>>> goto umem_release;
>>>>
>>>> cur_base += ret * PAGE_SIZE;
>>>> - npages -= ret;
>>>> -
>>>> - sg = ib_umem_add_sg_table(sg, page_list, ret,
>>>> - dma_get_max_seg_size(device->dma_device),
>>>> - &umem->sg_nents);
>>>> + npages -= ret;
>>>> + sg = __sg_alloc_table_from_pages(
>>>> + &umem->sg_head, page_list, ret, 0, ret << PAGE_SHIFT,
>>>> + dma_get_max_seg_size(device->dma_device), sg, npages,
>>>> + GFP_KERNEL);
>>>> + umem->sg_nents = umem->sg_head.nents;
>>>> + if (IS_ERR(sg)) {
>>>> + unpin_user_pages_dirty_lock(page_list, ret, 0);
>>>> + ret = PTR_ERR(sg);
>>>> + goto umem_release;
>>>> + }
>>>> }
>>>>
>>>> sg_mark_end(sg);
>>> Does it still need the sg_mark_end?
>> It is preserved here for correctness, the release logic doesn't rely on
>> this marker, but it is better to leave it.
> I mean, my read of __sg_alloc_table_from_pages() is that it already
> placed it, the final __alloc_table() does it?
>
> Jason

It marks the last allocated sge, but not the last populated sge (with page).