On 04/11/2016 02:32 PM, Christoph Hellwig wrote:
+/*
+ * Check if the device will use memory registration for this RW operation.
+ * We currently always use memory registrations for iWarp reads, and iWarp
+ * writes, but never for IB and RoCE.
+ *
+ * XXX: In the future we can hopefully fine tune this based on HCA driver
+ * input.
+ */
+static inline bool rdma_rw_io_needs_mr(struct ib_device *dev, u8 port_num,
+ enum dma_data_direction dir, int dma_nents)
+{
+ if (rdma_protocol_iwarp(dev, port_num) && dir == DMA_FROM_DEVICE)
+ return true;
+ if (unlikely(rdma_rw_force_mr))
+ return true;
+ return false;
+}
Please clarify the comment above this function. The way that comment is
written seems to contradict the code for iWARP writes.
+static int rdma_rw_init_one_mr(struct ib_qp *qp, u8 port_num,
+ struct rdma_rw_reg_ctx *reg, struct scatterlist *sg,
+ u32 sg_cnt, u32 offset)
+{
+ u32 pages_per_mr = rdma_rw_fr_page_list_len(qp->pd->device);
+ u32 nents = min(sg_cnt, pages_per_mr);
+ int count = 0, ret;
+
+ reg->mr = ib_mr_pool_get(qp, &qp->rdma_mrs);
+ if (!reg->mr)
+ return -EAGAIN;
+
+ if (reg->mr->need_inval) {
+ reg->inv_wr.opcode = IB_WR_LOCAL_INV;
+ reg->inv_wr.ex.invalidate_rkey = reg->mr->lkey;
+ reg->inv_wr.next = ®->reg_wr.wr;
+ count++;
+ } else {
+ reg->inv_wr.next = NULL;
+ }
+
+ ret = ib_map_mr_sg(reg->mr, sg, nents, offset, PAGE_SIZE);
+ if (ret < nents) {
+ ib_mr_pool_put(qp, &qp->rdma_mrs, reg->mr);
+ return -EINVAL;
+ }
The above code assumes that the length of each sg list element is lower
than or equal to mr->page_size. I think this is something that should be
documented since the block layer has to be configured explicitly to
ensure this.
+static int rdma_rw_init_mr_wrs(struct rdma_rw_ctx *ctx, struct ib_qp *qp,
+ u8 port_num, struct scatterlist *sg, u32 sg_cnt, u32 offset,
+ u64 remote_addr, u32 rkey, enum dma_data_direction dir)
+{
+ u32 pages_per_mr = rdma_rw_fr_page_list_len(qp->pd->device);
+ int i, j, ret = 0, count = 0;
+
+ ctx->nr_ops = (sg_cnt + pages_per_mr - 1) / pages_per_mr;
+ ctx->reg = kcalloc(ctx->nr_ops, sizeof(*ctx->reg), GFP_KERNEL);
+ if (!ctx->reg) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ for (i = 0; i < ctx->nr_ops; i++) {
+ struct rdma_rw_reg_ctx *prev = i ? &ctx->reg[i - 1] : NULL;
+ struct rdma_rw_reg_ctx *reg = &ctx->reg[i];
+ u32 nents = min(sg_cnt, pages_per_mr);
The same min(sg_cnt, pages_per_mr) computation occurs here and in
rdma_rw_init_one_mr(). Is there a way to avoid that duplication?
+#define RDMA_RW_SINGLE_WR 0
+#define RDMA_RW_MULTI_WR 1
+#define RDMA_RW_MR 2
The above constants are only used in the rw.c source file. Do we need
these constants in the header file or can these be moved into source
file rw.c?
Bart.
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