On 06.03.20 08:38, Vladimir Sementsov-Ogievskiy wrote:
Currently, block_copy operation lock the whole requested region. But
there is no reason to lock clusters, which are already copied, it will
disturb other parallel block_copy requests for no reason.
Let's instead do the following:
Lock only sub-region, which we are going to operate on. Then, after
copying all dirty sub-regions, we should wait for intersecting
requests block-copy, if they failed, we should retry these new dirty
clusters.
Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
Reviewed-by: Andrey Shinkevich <address@hidden>
---
block/block-copy.c | 128 ++++++++++++++++++++++++++++++++++++---------
1 file changed, 104 insertions(+), 24 deletions(-)
diff --git a/block/block-copy.c b/block/block-copy.c
index 2b29131653..d66b8eb691 100644
--- a/block/block-copy.c
+++ b/block/block-copy.c
[...]
+/* Called only on full-dirty region */
static void block_copy_inflight_req_begin(BlockCopyState *s,
BlockCopyInFlightReq *req,
int64_t offset, int64_t bytes)
{
+ assert(!find_conflicting_inflight_req(s, offset, bytes));
+
+ bdrv_reset_dirty_bitmap(s->copy_bitmap, offset, bytes);
+ s->in_flight_bytes += bytes;
+
req->offset = offset;
req->bytes = bytes;
qemu_co_queue_init(&req->wait_queue);
QLIST_INSERT_HEAD(&s->inflight_reqs, req, list);
}
-static void coroutine_fn block_copy_inflight_req_end(BlockCopyInFlightReq *req)
+/*
+ * block_copy_inflight_req_shrink
+ *
+ * Drop the tail of the request to be handled later. Set dirty bits back and
+ * wake up all requests waiting for us (may be some of them are not
intersecting
+ * with shrunk request)
+ */
+static void coroutine_fn block_copy_inflight_req_shrink(BlockCopyState *s,
+ BlockCopyInFlightReq *req, int64_t new_bytes)
{
+ if (new_bytes == req->bytes) {
+ return;
+ }
+
+ assert(new_bytes > 0 && new_bytes < req->bytes);
+
+ bdrv_set_dirty_bitmap(s->copy_bitmap,
+ req->offset + new_bytes, req->bytes - new_bytes);
I think we need to reduce in_flight_bytes here.
+
+ req->bytes = new_bytes;
+ qemu_co_queue_restart_all(&req->wait_queue);
+}
+
+static void coroutine_fn block_copy_inflight_req_end(BlockCopyState *s,
+ BlockCopyInFlightReq *req,
+ int ret)
+{
+ s->in_flight_bytes -= req->bytes;
+ if (ret < 0) {
+ bdrv_set_dirty_bitmap(s->copy_bitmap, req->offset, req->bytes);
+ }
QLIST_REMOVE(req, list);
qemu_co_queue_restart_all(&req->wait_queue);
}
[...]
@@ -432,7 +479,40 @@ int coroutine_fn block_copy(BlockCopyState *s,
bytes -= cur_bytes;
}
- block_copy_inflight_req_end(&req);
+ return found_dirty;
+}
+
+/*
+ * block_copy
+ *
+ * Copy requested region, accordingly to dirty bitmap.
+ * Collaborate with parallel block_copy requests: if they success it help us.
If
s/success/succeed/, s/it help/it will help/
+ * they fail, we retry not-copied regions. So, if we return error, it means
that
s/retry/will retry/
(In theory also s/it means/it will mean/, but I suppose that also works
as-is.)
+ * io operation failed in context of _this_ block_copy call, not some parallel
Perhaps rather “some I/O operation failed in the context of […]”?
+ * operation.
+ */
+int coroutine_fn block_copy(BlockCopyState *s, int64_t offset, int64_t bytes,
+ bool *error_is_read)
+{
+ int ret;
+
+ do {
+ ret = block_copy_dirty_clusters(s, offset, bytes, error_is_read);
+
+ if (ret == 0) {
+ ret = block_copy_wait_one(s, offset, bytes);
+ }
+
+ /*
+ * We retry in two cases:
+ * 1. Some progress done
+ * Something was copied, which means that there were yield points
+ * and some new dirty bits may have appeared (due to failed parallel
+ * block-copy requests).
+ * 2. We have waited for some intersecting block-copy request
+ * It may have failed and produced new dirty bits.
+ */
+ } while (ret > 0);
return ret;
}
This new code looks good.
Max