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block/block-copy: reduce intersecting request lock 

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>
Message-Id: <20200311103004.7649-9-vsementsov@virtuozzo.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Vladimir Sementsov-Ogievskiy 2020-03-11 13:30:03 +03:00 committed by Max Reitz
parent 8719091f9d
commit 5332e5d210
1 changed files with 105 additions and 24 deletions
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129
block/block-copy.c
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@ -39,29 +39,72 @@ 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);
s->in_flight_bytes -= req->bytes - new_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 +400,19 @@ 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 +424,8 @@ 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 +435,8 @@ 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 +446,14 @@ 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 +463,15 @@ 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 +480,40 @@ 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 succeed it will help
* us. If they fail, we will retry not-copied regions. So, if we return error,
* it means that some I/O 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;
}