Re: [PATCH v5 07/13] SIW application buffer management

[Jason Gunthorpe <jgg@xxxxxxxx>]

On Tue, Feb 19, 2019 at 11:08:57AM +0100, Bernard Metzler wrote:
> +struct siw_umem *siw_umem_get(u64 start, u64 len)
> +{
> +	struct siw_umem *umem;
> +	u64 first_page_va;
> +	unsigned long mlock_limit;
> +	int num_pages, num_chunks, i, rv = 0;
> +
> +	if (!can_do_mlock())
> +		return ERR_PTR(-EPERM);
> +
> +	if (!len)
> +		return ERR_PTR(-EINVAL);
> +
> +	first_page_va = start & PAGE_MASK;
> +	num_pages = PAGE_ALIGN(start + len - first_page_va) >> PAGE_SHIFT;
> +	num_chunks = (num_pages >> CHUNK_SHIFT) + 1;
> +
> +	umem = kzalloc(sizeof(*umem), GFP_KERNEL);
> +	if (!umem)
> +		return ERR_PTR(-ENOMEM);
> +
> +	umem->pid = get_task_pid(current, PIDTYPE_PID);
> +
> +	down_write(&current->mm->mmap_sem);
> +
> +	mlock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
> +
> +	if (num_pages + atomic64_read(&current->mm->pinned_vm) > mlock_limit) {
> +		rv = -ENOMEM;
> +		goto out;
> +	}
> +	umem->fp_addr = first_page_va;
> +
> +	umem->page_chunk = kcalloc(num_chunks, sizeof(struct siw_page_chunk),
> +				   GFP_KERNEL);
> +	if (!umem->page_chunk) {
> +		rv = -ENOMEM;
> +		goto out;
> +	}
> +	for (i = 0; num_pages; i++) {
> +		int got, nents = min_t(int, num_pages, PAGES_PER_CHUNK);
> +
> +		umem->page_chunk[i].p = kcalloc(nents, sizeof(struct page *),
> +						GFP_KERNEL);
> +		if (!umem->page_chunk[i].p) {
> +			rv = -ENOMEM;
> +			goto out;
> +		}
> +		got = 0;
> +		while (nents) {
> +			struct page **plist = &umem->page_chunk[i].p[got];
> +
> +			rv = get_user_pages(first_page_va, nents, FOLL_WRITE,
> +					    plist, NULL);
> +			if (rv < 0)
> +				goto out;
> +
> +			umem->num_pages += rv;
> +			atomic64_add(rv, &current->mm->pinned_vm);
> +			first_page_va += rv * PAGE_SIZE;
> +			nents -= rv;
> +			got += rv;
> +		}
> +		num_pages -= got;
> +	}

Actually why isn't this just using umem_get?

rxe managed it. IIRC you set the dma_ops properly and the dma_map does
nothing, so this boils down to the same as umem get.

Jason