Re: [Qemu-devel] [PATCH v3 17/20] backup: Switch backup_run() to byte-based

[Jeff Cody <jcody@redhat.com>]

On Tue, Jun 27, 2017 at 02:24:55PM -0500, Eric Blake wrote:
> We are gradually converting to byte-based interfaces, as they are
> easier to reason about than sector-based.  Change the internal
> loop iteration of backups to track by bytes instead of sectors
> (although we are still guaranteed that we iterate by steps that
> are cluster-aligned).
> 
> 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 | 32 +++++++++++++++-----------------
>  1 file changed, 15 insertions(+), 17 deletions(-)
> 
> diff --git a/block/backup.c b/block/backup.c
> index c029d44..04def91 100644
> --- a/block/backup.c
> +++ b/block/backup.c
> @@ -370,11 +370,10 @@ static int coroutine_fn backup_run_incremental(BackupBlockJob *job)
>      int ret = 0;
>      int clusters_per_iter;
>      uint32_t granularity;
> -    int64_t sector;
> +    int64_t offset;
>      int64_t cluster;
>      int64_t end;
>      int64_t last_cluster = -1;
> -    int64_t sectors_per_cluster = cluster_size_sectors(job);
>      BdrvDirtyBitmapIter *dbi;
> 
>      granularity = bdrv_dirty_bitmap_granularity(job->sync_bitmap);
> @@ -382,8 +381,8 @@ static int coroutine_fn backup_run_incremental(BackupBlockJob *job)
>      dbi = bdrv_dirty_iter_new(job->sync_bitmap, 0);
> 
>      /* Find the next dirty sector(s) */
> -    while ((sector = bdrv_dirty_iter_next(dbi)) != -1) {
> -        cluster = sector / sectors_per_cluster;
> +    while ((offset = bdrv_dirty_iter_next(dbi) * BDRV_SECTOR_SIZE) >= 0) {
> +        cluster = offset / job->cluster_size;
> 
>          /* Fake progress updates for any clusters we skipped */
>          if (cluster != last_cluster + 1) {
> @@ -410,7 +409,8 @@ static int coroutine_fn backup_run_incremental(BackupBlockJob *job)
>          /* If the bitmap granularity is smaller than the backup granularity,
>           * we need to advance the iterator pointer to the next cluster. */
>          if (granularity < job->cluster_size) {
> -            bdrv_set_dirty_iter(dbi, cluster * sectors_per_cluster);
> +            bdrv_set_dirty_iter(dbi,
> +                                cluster * job->cluster_size / BDRV_SECTOR_SIZE);
>          }
> 
>          last_cluster = cluster - 1;
> @@ -432,17 +432,15 @@ static void coroutine_fn backup_run(void *opaque)
>      BackupBlockJob *job = opaque;
>      BackupCompleteData *data;
>      BlockDriverState *bs = blk_bs(job->common.blk);
> -    int64_t start, end;
> +    int64_t offset;
>      int64_t sectors_per_cluster = cluster_size_sectors(job);
>      int ret = 0;
> 
>      QLIST_INIT(&job->inflight_reqs);
>      qemu_co_rwlock_init(&job->flush_rwlock);
> 
> -    start = 0;
> -    end = DIV_ROUND_UP(job->common.len, job->cluster_size);
> -
> -    job->done_bitmap = bitmap_new(end);
> +    job->done_bitmap = bitmap_new(DIV_ROUND_UP(job->common.len,
> +                                               job->cluster_size));
> 
>      job->before_write.notify = backup_before_write_notify;
>      bdrv_add_before_write_notifier(bs, &job->before_write);
> @@ -457,7 +455,8 @@ static void coroutine_fn backup_run(void *opaque)
>          ret = backup_run_incremental(job);
>      } else {
>          /* Both FULL and TOP SYNC_MODE's require copying.. */
> -        for (; start < end; start++) {
> +        for (offset = 0; offset < job->common.len;
> +             offset += job->cluster_size) {
>              bool error_is_read;
>              int alloced = 0;
> 
> @@ -480,8 +479,8 @@ static void coroutine_fn backup_run(void *opaque)
>                       * needed but at some point that is always the case. */
>                      alloced =
>                          bdrv_is_allocated(bs,
> -                                start * sectors_per_cluster + i,
> -                                sectors_per_cluster - i, &n);
> +                                          (offset >> BDRV_SECTOR_BITS) + i,
> +                                          sectors_per_cluster - i, &n);
>                      i += n;
> 
>                      if (alloced || n == 0) {
> @@ -499,9 +498,8 @@ static void coroutine_fn backup_run(void *opaque)
>              if (alloced < 0) {
>                  ret = alloced;
>              } else {
> -                ret = backup_do_cow(job, start * job->cluster_size,
> -                                    job->cluster_size, &error_is_read,
> -                                    false);
> +                ret = backup_do_cow(job, offset, job->cluster_size,
> +                                    &error_is_read, false);
>              }
>              if (ret < 0) {
>                  /* Depending on error action, fail now or retry cluster */
> @@ -510,7 +508,7 @@ static void coroutine_fn backup_run(void *opaque)
>                  if (action == BLOCK_ERROR_ACTION_REPORT) {
>                      break;
>                  } else {
> -                    start--;
> +                    offset -= job->cluster_size;
>                      continue;
>                  }
>              }
> -- 
> 2.9.4
>