Thread (31 messages) 31 messages, 4 authors, 2023-08-15

Re: [dm-devel] [PATCH v14 03/11] block: add copy offload support

From: Nitesh Shetty <hidden>
Date: 2023-08-14 17:03:06
Also in: dm-devel, linux-block, linux-fsdevel, linux-nvme, lkml

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
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