Re: [Qemu-devel] [PATCH v3 16/20] backup: Switch backup_do_cow() to byte-based

[Jeff Cody <jcody@redhat.com>]

On Tue, Jun 27, 2017 at 02:24:54PM -0500, Eric Blake wrote:
> We are gradually converting to byte-based interfaces, as they are
> easier to reason about than sector-based.  Convert another internal
> function (no semantic change).
> 
> Signed-off-by: Eric Blake <eblake@redhat.com>
> Reviewed-by: John Snow <jsnow@redhat.com>
> 

Reviewed-by: Jeff Cody <jcody@redhat.com>

> ---
> v2: no change
> ---
>  block/backup.c | 62 ++++++++++++++++++++++++----------------------------------
>  1 file changed, 26 insertions(+), 36 deletions(-)
> 
> diff --git a/block/backup.c b/block/backup.c
> index cfbd921..c029d44 100644
> --- a/block/backup.c
> +++ b/block/backup.c
> @@ -91,7 +91,7 @@ static void cow_request_end(CowRequest *req)
>  }
> 
>  static int coroutine_fn backup_do_cow(BackupBlockJob *job,
> -                                      int64_t sector_num, int nb_sectors,
> +                                      int64_t offset, uint64_t bytes,
>                                        bool *error_is_read,
>                                        bool is_write_notifier)
>  {
> @@ -101,34 +101,28 @@ static int coroutine_fn backup_do_cow(BackupBlockJob *job,
>      QEMUIOVector bounce_qiov;
>      void *bounce_buffer = NULL;
>      int ret = 0;
> -    int64_t sectors_per_cluster = cluster_size_sectors(job);
> -    int64_t start, end; /* clusters */
> +    int64_t start, end; /* bytes */
>      int n; /* bytes */
> 
>      qemu_co_rwlock_rdlock(&job->flush_rwlock);
> 
> -    start = sector_num / sectors_per_cluster;
> -    end = DIV_ROUND_UP(sector_num + nb_sectors, sectors_per_cluster);
> +    start = QEMU_ALIGN_DOWN(offset, job->cluster_size);
> +    end = QEMU_ALIGN_UP(bytes + offset, job->cluster_size);
> 
> -    trace_backup_do_cow_enter(job, start * job->cluster_size,
> -                              sector_num * BDRV_SECTOR_SIZE,
> -                              nb_sectors * BDRV_SECTOR_SIZE);
> +    trace_backup_do_cow_enter(job, start, offset, bytes);
> 
> -    wait_for_overlapping_requests(job, start * job->cluster_size,
> -                                  end * job->cluster_size);
> -    cow_request_begin(&cow_request, job, start * job->cluster_size,
> -                      end * job->cluster_size);
> +    wait_for_overlapping_requests(job, start, end);
> +    cow_request_begin(&cow_request, job, start, end);
> 
> -    for (; start < end; start++) {
> -        if (test_bit(start, job->done_bitmap)) {
> -            trace_backup_do_cow_skip(job, start * job->cluster_size);
> +    for (; start < end; start += job->cluster_size) {
> +        if (test_bit(start / job->cluster_size, job->done_bitmap)) {
> +            trace_backup_do_cow_skip(job, start);
>              continue; /* already copied */
>          }
> 
> -        trace_backup_do_cow_process(job, start * job->cluster_size);
> +        trace_backup_do_cow_process(job, start);
> 
> -        n = MIN(job->cluster_size,
> -                job->common.len - start * job->cluster_size);
> +        n = MIN(job->cluster_size, job->common.len - start);
> 
>          if (!bounce_buffer) {
>              bounce_buffer = blk_blockalign(blk, job->cluster_size);
> @@ -137,11 +131,10 @@ static int coroutine_fn backup_do_cow(BackupBlockJob *job,
>          iov.iov_len = n;
>          qemu_iovec_init_external(&bounce_qiov, &iov, 1);
> 
> -        ret = blk_co_preadv(blk, start * job->cluster_size,
> -                            bounce_qiov.size, &bounce_qiov,
> +        ret = blk_co_preadv(blk, start, bounce_qiov.size, &bounce_qiov,
>                              is_write_notifier ? BDRV_REQ_NO_SERIALISING : 0);
>          if (ret < 0) {
> -            trace_backup_do_cow_read_fail(job, start * job->cluster_size, ret);
> +            trace_backup_do_cow_read_fail(job, start, ret);
>              if (error_is_read) {
>                  *error_is_read = true;
>              }
> @@ -149,22 +142,22 @@ static int coroutine_fn backup_do_cow(BackupBlockJob *job,
>          }
> 
>          if (buffer_is_zero(iov.iov_base, iov.iov_len)) {
> -            ret = blk_co_pwrite_zeroes(job->target, start * job->cluster_size,
> +            ret = blk_co_pwrite_zeroes(job->target, start,
>                                         bounce_qiov.size, BDRV_REQ_MAY_UNMAP);
>          } else {
> -            ret = blk_co_pwritev(job->target, start * job->cluster_size,
> +            ret = blk_co_pwritev(job->target, start,
>                                   bounce_qiov.size, &bounce_qiov,
>                                   job->compress ? BDRV_REQ_WRITE_COMPRESSED : 0);
>          }
>          if (ret < 0) {
> -            trace_backup_do_cow_write_fail(job, start * job->cluster_size, ret);
> +            trace_backup_do_cow_write_fail(job, start, ret);
>              if (error_is_read) {
>                  *error_is_read = false;
>              }
>              goto out;
>          }
> 
> -        set_bit(start, job->done_bitmap);
> +        set_bit(start / job->cluster_size, job->done_bitmap);
> 
>          /* Publish progress, guest I/O counts as progress too.  Note that the
>           * offset field is an opaque progress value, it is not a disk offset.
> @@ -180,8 +173,7 @@ out:
> 
>      cow_request_end(&cow_request);
> 
> -    trace_backup_do_cow_return(job, sector_num * BDRV_SECTOR_SIZE,
> -                               nb_sectors * BDRV_SECTOR_SIZE, ret);
> +    trace_backup_do_cow_return(job, offset, bytes, ret);
> 
>      qemu_co_rwlock_unlock(&job->flush_rwlock);
> 
> @@ -194,14 +186,12 @@ static int coroutine_fn backup_before_write_notify(
>  {
>      BackupBlockJob *job = container_of(notifier, BackupBlockJob, before_write);
>      BdrvTrackedRequest *req = opaque;
> -    int64_t sector_num = req->offset >> BDRV_SECTOR_BITS;
> -    int nb_sectors = req->bytes >> BDRV_SECTOR_BITS;
> 
>      assert(req->bs == blk_bs(job->common.blk));
> -    assert((req->offset & (BDRV_SECTOR_SIZE - 1)) == 0);
> -    assert((req->bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
> +    assert(QEMU_IS_ALIGNED(req->offset, BDRV_SECTOR_SIZE));
> +    assert(QEMU_IS_ALIGNED(req->bytes, BDRV_SECTOR_SIZE));
> 
> -    return backup_do_cow(job, sector_num, nb_sectors, NULL, true);
> +    return backup_do_cow(job, req->offset, req->bytes, NULL, true);
>  }
> 
>  static void backup_set_speed(BlockJob *job, int64_t speed, Error **errp)
> @@ -406,8 +396,8 @@ static int coroutine_fn backup_run_incremental(BackupBlockJob *job)
>                  if (yield_and_check(job)) {
>                      goto out;
>                  }
> -                ret = backup_do_cow(job, cluster * sectors_per_cluster,
> -                                    sectors_per_cluster, &error_is_read,
> +                ret = backup_do_cow(job, cluster * job->cluster_size,
> +                                    job->cluster_size, &error_is_read,
>                                      false);
>                  if ((ret < 0) &&
>                      backup_error_action(job, error_is_read, -ret) ==
> @@ -509,8 +499,8 @@ static void coroutine_fn backup_run(void *opaque)
>              if (alloced < 0) {
>                  ret = alloced;
>              } else {
> -                ret = backup_do_cow(job, start * sectors_per_cluster,
> -                                    sectors_per_cluster, &error_is_read,
> +                ret = backup_do_cow(job, start * job->cluster_size,
> +                                    job->cluster_size, &error_is_read,
>                                      false);
>              }
>              if (ret < 0) {
> -- 
> 2.9.4
>