Commit 5332e5d2 authored by Vladimir Sementsov-Ogievskiy's avatar Vladimir Sementsov-Ogievskiy Committed by Max Reitz
Browse files

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: default avatarVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: default avatarAndrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Message-Id: <20200311103004.7649-9-vsementsov@virtuozzo.com>
Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
parent 8719091f

block/block-copy.c

+105 −24
Original line number Diff line number Diff line
@@ -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,

/*

 * 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,

/*

 * 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;

}