io_uring/zcrx: pass ifq to io_zcrx_alloc_fallback()

io_zcrx_copy_chunk() doesn't and shouldn't care from which area the
buffer is allocated, don't try to resolve the area in it but pass the
ifq to io_zcrx_alloc_fallback() and let it handle it. Also rename it for
more clarity.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: isilence

io_uring/zcrx.c

@@ -957,10 +957,14 @@ static bool io_zcrx_queue_cqe(struct io_kiocb *req, struct net_iov *niov,
 	return true;
 }
 
-static struct net_iov *io_zcrx_alloc_fallback(struct io_zcrx_area *area)
+static struct net_iov *io_alloc_fallback_niov(struct io_zcrx_ifq *ifq)
 {
+	struct io_zcrx_area *area = ifq->area;
 	struct net_iov *niov = NULL;
 
+	if (area->mem.is_dmabuf)
+		return NULL;
+
 	spin_lock_bh(&area->freelist_lock);
 	if (area->free_count)
 		niov = __io_zcrx_get_free_niov(area);
@@ -1020,19 +1024,15 @@ static ssize_t io_zcrx_copy_chunk(struct io_kiocb *req, struct io_zcrx_ifq *ifq,
 				  struct page *src_page, unsigned int src_offset,
 				  size_t len)
 {
-	struct io_zcrx_area *area = ifq->area;
 	size_t copied = 0;
 	int ret = 0;
 
-	if (area->mem.is_dmabuf)
-		return -EFAULT;
-
 	while (len) {
 		struct io_copy_cache cc;
 		struct net_iov *niov;
 		size_t n;
 
-		niov = io_zcrx_alloc_fallback(area);
+		niov = io_alloc_fallback_niov(ifq);
 		if (!niov) {
 			ret = -ENOMEM;
 			break;