On Sat, Aug 12, 2023 at 3:10 AM Bart Van Assche [off-list ref] wrote:

On 8/11/23 03:52, Nitesh Shetty wrote:

quoted

+ * Description:
+ *   Copy source offset to destination offset within block device, using
+ *   device's native copy offload feature.

Offloading the copy operation is not guaranteed so I think that needs to
be reflected in the above comment.

Acked.

quoted

+ *   We perform copy operation by sending 2 bio's.
+ *   1. We take a plug and send a REQ_OP_COPY_SRC bio along with source
+ *   sector and length. Once this bio reaches request layer, we form a
+ *   request and wait for dst bio to arrive.

What will happen if the queue depth of the request queue at the bottom
is one?

For any reason if a request reaches the driver with only one of the src/dst bio,
copy will fail. This design requires only one request to do a copy,
so it should work fine.

quoted

+             blk_start_plug(&plug);
+             dst_bio = blk_next_bio(src_bio, bdev, 0, REQ_OP_COPY_DST, gfp);

blk_next_bio() can return NULL so its return value should be checked.

Acked.

Thank you,
Nitesh Shetty