io_uring/zcrx: always dma map in advance

zcrx was originally establisihing dma mappings at a late stage when it
was being bound to a page pool. Dma-buf couldn't work this way, so it's
initialised during area creation.

It's messy having them do it at different spots, just move everything to
the area creation time.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://patch.msgid.link/334092a2cbdd4aabd7c025050aa99f05ace89bb5.1774261953.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: isilence

io_uring/zcrx.c

@@ -194,6 +194,7 @@ static int io_import_umem(struct io_zcrx_ifq *ifq,
 {
 	struct page **pages;
 	int nr_pages, ret;
+	bool mapped = false;
 
 	if (area_reg->dmabuf_fd)
 		return -EINVAL;
@@ -210,6 +211,12 @@ static int io_import_umem(struct io_zcrx_ifq *ifq,
 	if (ret)
 		goto out_err;
 
+	ret = dma_map_sgtable(ifq->dev, &mem->page_sg_table,
+			      DMA_FROM_DEVICE, IO_DMA_ATTR);
+	if (ret < 0)
+		goto out_err;
+	mapped = true;
+
 	mem->account_pages = io_count_account_pages(pages, nr_pages);
 	ret = io_account_mem(ifq->user, ifq->mm_account, mem->account_pages);
 	if (ret < 0) {
@@ -223,6 +230,9 @@ static int io_import_umem(struct io_zcrx_ifq *ifq,
 	mem->size = area_reg->len;
 	return ret;
 out_err:
+	if (mapped)
+		dma_unmap_sgtable(ifq->dev, &mem->page_sg_table,
+				  DMA_FROM_DEVICE, IO_DMA_ATTR);
 	sg_free_table(&mem->page_sg_table);
 	unpin_user_pages(pages, nr_pages);
 	kvfree(pages);
@@ -288,30 +298,6 @@ static void io_zcrx_unmap_area(struct io_zcrx_ifq *ifq,
 	}
 }
 
-static int io_zcrx_map_area(struct io_zcrx_ifq *ifq, struct io_zcrx_area *area)
-{
-	int ret;
-
-	guard(mutex)(&ifq->pp_lock);
-	if (area->is_mapped)
-		return 0;
-
-	if (!area->mem.is_dmabuf) {
-		ret = dma_map_sgtable(ifq->dev, &area->mem.page_sg_table,
-				      DMA_FROM_DEVICE, IO_DMA_ATTR);
-		if (ret < 0)
-			return ret;
-	}
-
-	ret = io_populate_area_dma(ifq, area);
-	if (ret && !area->mem.is_dmabuf)
-		dma_unmap_sgtable(ifq->dev, &area->mem.page_sg_table,
-				  DMA_FROM_DEVICE, IO_DMA_ATTR);
-	if (ret == 0)
-		area->is_mapped = true;
-	return ret;
-}
-
 static void io_zcrx_sync_for_device(struct page_pool *pool,
 				    struct net_iov *niov)
 {
@@ -464,6 +450,7 @@ static int io_zcrx_create_area(struct io_zcrx_ifq *ifq,
 	ret = io_import_area(ifq, &area->mem, area_reg);
 	if (ret)
 		goto err;
+	area->is_mapped = true;
 
 	if (buf_size_shift > io_area_max_shift(&area->mem)) {
 		ret = -ERANGE;
@@ -499,6 +486,10 @@ static int io_zcrx_create_area(struct io_zcrx_ifq *ifq,
 		niov->type = NET_IOV_IOURING;
 	}
 
+	ret = io_populate_area_dma(ifq, area);
+	if (ret)
+		goto err;
+
 	area->free_count = nr_iovs;
 	/* we're only supporting one area per ifq for now */
 	area->area_id = 0;
@@ -1082,7 +1073,6 @@ static bool io_pp_zc_release_netmem(struct page_pool *pp, netmem_ref netmem)
 static int io_pp_zc_init(struct page_pool *pp)
 {
 	struct io_zcrx_ifq *ifq = io_pp_to_ifq(pp);
-	int ret;
 
 	if (WARN_ON_ONCE(!ifq))
 		return -EINVAL;
@@ -1095,10 +1085,6 @@ static int io_pp_zc_init(struct page_pool *pp)
 	if (pp->p.dma_dir != DMA_FROM_DEVICE)
 		return -EOPNOTSUPP;
 
-	ret = io_zcrx_map_area(ifq, ifq->area);
-	if (ret)
-		return ret;
-
 	refcount_inc(&ifq->refs);
 	return 0;
 }