Re: [PATCH v20 02/12] Add infrastructure for copy offload in block and request layer.

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On 5/20/24 03:20, Nitesh Shetty wrote:
Upon arrival of source bio we merge these two bio's and send
corresponding request down to device driver.

bios with different operation types must not be merged.

+static enum bio_merge_status bio_attempt_copy_offload_merge(struct request *req,
+							    struct bio *bio)
+{
+	if (req->__data_len != bio->bi_iter.bi_size)
+		return BIO_MERGE_FAILED;
+
+	req->biotail->bi_next = bio;
+	req->biotail = bio;
+	req->nr_phys_segments++;
+	req->__data_len += bio->bi_iter.bi_size;
+
+	return BIO_MERGE_OK;
+}

This function appends a bio to a request. Hence, the name of this function is
wrong.

@@ -1085,6 +1124,8 @@ static enum bio_merge_status blk_attempt_bio_merge(struct request_queue *q,
  		break;
  	case ELEVATOR_DISCARD_MERGE:
  		return bio_attempt_discard_merge(q, rq, bio);
+	case ELEVATOR_COPY_OFFLOAD_MERGE:
+		return bio_attempt_copy_offload_merge(rq, bio);
  	default:
  		return BIO_MERGE_NONE;
  	}

Is any code added in this patch series that causes an I/O scheduler to return
ELEVATOR_COPY_OFFLOAD_MERGE?

+static inline bool blk_copy_offload_mergable(struct request *req,
+					     struct bio *bio)
+{
+	return (req_op(req) == REQ_OP_COPY_DST &&
+		bio_op(bio) == REQ_OP_COPY_SRC);
+}

bios with different operation types must not be merged. Please rename this function.

+static inline bool op_is_copy(blk_opf_t op)
+{
+	return ((op & REQ_OP_MASK) == REQ_OP_COPY_SRC ||
+		(op & REQ_OP_MASK) == REQ_OP_COPY_DST);
+}

The above function is not used in this patch. Please introduce new functions in the
patch in which these are used for the first time.

Thanks,

Bart.





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