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 <vsementsov@virtuozzo.com>
Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
---
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
@@ -39,29 +39,71 @@ static BlockCopyInFlightReq *find_conflicting_inflight_req(BlockCopyState *s,
return NULL;
}
-static void coroutine_fn block_copy_wait_inflight_reqs(BlockCopyState *s,
- int64_t offset,
- int64_t bytes)
+/*
+ * If there are no intersecting requests return false. Otherwise, wait for the
+ * first found intersecting request to finish and return true.
+ */
+static bool coroutine_fn block_copy_wait_one(BlockCopyState *s, int64_t offset,
+ int64_t bytes)
{
- BlockCopyInFlightReq *req;
+ BlockCopyInFlightReq *req = find_conflicting_inflight_req(s, offset, bytes);
- while ((req = find_conflicting_inflight_req(s, offset, bytes))) {
- qemu_co_queue_wait(&req->wait_queue, NULL);
+ if (!req) {
+ return false;
}
+
+ qemu_co_queue_wait(&req->wait_queue, NULL);
+
+ return true;
}
+/* 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);
+
+ 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);
}
@@ -357,12 +399,19 @@ int64_t block_copy_reset_unallocated(BlockCopyState *s,
return ret;
}
-int coroutine_fn block_copy(BlockCopyState *s,
- int64_t offset, int64_t bytes,
- bool *error_is_read)
+/*
+ * block_copy_dirty_clusters
+ *
+ * Copy dirty clusters in @offset/@bytes range.
+ * Returns 1 if dirty clusters found and successfully copied, 0 if no dirty
+ * clusters found and -errno on failure.
+ */
+static int coroutine_fn block_copy_dirty_clusters(BlockCopyState *s,
+ int64_t offset, int64_t bytes,
+ bool *error_is_read)
{
int ret = 0;
- BlockCopyInFlightReq req;
+ bool found_dirty = false;
/*
* block_copy() user is responsible for keeping source and target in same
@@ -374,10 +423,8 @@ int coroutine_fn block_copy(BlockCopyState *s,
assert(QEMU_IS_ALIGNED(offset, s->cluster_size));
assert(QEMU_IS_ALIGNED(bytes, s->cluster_size));
- block_copy_wait_inflight_reqs(s, offset, bytes);
- block_copy_inflight_req_begin(s, &req, offset, bytes);
-
while (bytes) {
+ BlockCopyInFlightReq req;
int64_t next_zero, cur_bytes, status_bytes;
if (!bdrv_dirty_bitmap_get(s->copy_bitmap, offset)) {
@@ -387,6 +434,8 @@ int coroutine_fn block_copy(BlockCopyState *s,
continue; /* already copied */
}
+ found_dirty = true;
+
cur_bytes = MIN(bytes, s->copy_size);
next_zero = bdrv_dirty_bitmap_next_zero(s->copy_bitmap, offset,
@@ -396,10 +445,14 @@ int coroutine_fn block_copy(BlockCopyState *s,
assert(next_zero < offset + cur_bytes); /* no need to do MIN() */
cur_bytes = next_zero - offset;
}
+ block_copy_inflight_req_begin(s, &req, offset, cur_bytes);
ret = block_copy_block_status(s, offset, cur_bytes, &status_bytes);
+ assert(ret >= 0); /* never fail */
+ cur_bytes = MIN(cur_bytes, status_bytes);
+ block_copy_inflight_req_shrink(s, &req, cur_bytes);
if (s->skip_unallocated && !(ret & BDRV_BLOCK_ALLOCATED)) {
- bdrv_reset_dirty_bitmap(s->copy_bitmap, offset, status_bytes);
+ block_copy_inflight_req_end(s, &req, 0);
progress_set_remaining(s->progress,
bdrv_get_dirty_count(s->copy_bitmap) +
s->in_flight_bytes);
@@ -409,21 +462,15 @@ int coroutine_fn block_copy(BlockCopyState *s,
continue;
}
- cur_bytes = MIN(cur_bytes, status_bytes);
-
trace_block_copy_process(s, offset);
- bdrv_reset_dirty_bitmap(s->copy_bitmap, offset, cur_bytes);
- s->in_flight_bytes += cur_bytes;
-
co_get_from_shres(s->mem, cur_bytes);
ret = block_copy_do_copy(s, offset, cur_bytes, ret & BDRV_BLOCK_ZERO,
error_is_read);
co_put_to_shres(s->mem, cur_bytes);
- s->in_flight_bytes -= cur_bytes;
+ block_copy_inflight_req_end(s, &req, ret);
if (ret < 0) {
- bdrv_set_dirty_bitmap(s->copy_bitmap, offset, cur_bytes);
- break;
+ return ret;
}
progress_work_done(s->progress, cur_bytes);
@@ -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
+ * they fail, we retry not-copied regions. So, if we return error, it means that
+ * io operation failed in context of _this_ block_copy call, not some parallel
+ * 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;
}
--
2.21.0
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 <vsementsov@virtuozzo.com>
> Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
> ---
> 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
10.03.2020 18:32, Max Reitz wrote:
> 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 <vsementsov@virtuozzo.com>
>> Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
>> ---
>> 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.
Yes, you are right, thanks!
>
>> +
>> + 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
>
--
Best regards,
Vladimir
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