Re: [Qemu-devel] [PATCH v3 15/20] backup: Switch block_backup.h to byte-based

[Jeff Cody]

On Tue, Jun 27, 2017 at 02:24:53PM -0500, Eric Blake wrote:
> We are gradually converting to byte-based interfaces, as they are
> easier to reason about than sector-based.  Continue by converting
> the public interface to backup jobs (no semantic change), including
> a change to CowRequest to track by bytes instead of cluster indices.
> 
> Note that this does not change the difference between the public
> interface (starting point, and size of the subsequent range) and
> the internal interface (starting and end points).
> 
> Signed-off-by: Eric Blake <address@hidden>
> Reviewed-by: John Snow <address@hidden>
> 

Reviewed-by: Jeff Cody <address@hidden>

> ---
> v2: change a couple more parameter names
> ---
>  include/block/block_backup.h | 11 +++++------
>  block/backup.c               | 33 ++++++++++++++++-----------------
>  block/replication.c          | 12 ++++++++----
>  3 files changed, 29 insertions(+), 27 deletions(-)
> 
> diff --git a/include/block/block_backup.h b/include/block/block_backup.h
> index 8a75947..994a3bd 100644
> --- a/include/block/block_backup.h
> +++ b/include/block/block_backup.h
> @@ -21,17 +21,16 @@
>  #include "block/block_int.h"
> 
>  typedef struct CowRequest {
> -    int64_t start;
> -    int64_t end;
> +    int64_t start_byte;
> +    int64_t end_byte;
>      QLIST_ENTRY(CowRequest) list;
>      CoQueue wait_queue; /* coroutines blocked on this request */
>  } CowRequest;
> 
> -void backup_wait_for_overlapping_requests(BlockJob *job, int64_t sector_num,
> -                                          int nb_sectors);
> +void backup_wait_for_overlapping_requests(BlockJob *job, int64_t offset,
> +                                          uint64_t bytes);
>  void backup_cow_request_begin(CowRequest *req, BlockJob *job,
> -                              int64_t sector_num,
> -                              int nb_sectors);
> +                              int64_t offset, uint64_t bytes);
>  void backup_cow_request_end(CowRequest *req);
> 
>  void backup_do_checkpoint(BlockJob *job, Error **errp);
> diff --git a/block/backup.c b/block/backup.c
> index 4e64710..cfbd921 100644
> --- a/block/backup.c
> +++ b/block/backup.c
> @@ -55,7 +55,7 @@ static inline int64_t cluster_size_sectors(BackupBlockJob 
> *job)
> 
>  /* See if in-flight requests overlap and wait for them to complete */
>  static void coroutine_fn wait_for_overlapping_requests(BackupBlockJob *job,
> -                                                       int64_t start,
> +                                                       int64_t offset,
>                                                         int64_t end)
>  {
>      CowRequest *req;
> @@ -64,7 +64,7 @@ static void coroutine_fn 
> wait_for_overlapping_requests(BackupBlockJob *job,
>      do {
>          retry = false;
>          QLIST_FOREACH(req, &job->inflight_reqs, list) {
> -            if (end > req->start && start < req->end) {
> +            if (end > req->start_byte && offset < req->end_byte) {
>                  qemu_co_queue_wait(&req->wait_queue, NULL);
>                  retry = true;
>                  break;
> @@ -75,10 +75,10 @@ static void coroutine_fn 
> wait_for_overlapping_requests(BackupBlockJob *job,
> 
>  /* Keep track of an in-flight request */
>  static void cow_request_begin(CowRequest *req, BackupBlockJob *job,
> -                                     int64_t start, int64_t end)
> +                              int64_t offset, int64_t end)
>  {
> -    req->start = start;
> -    req->end = end;
> +    req->start_byte = offset;
> +    req->end_byte = end;
>      qemu_co_queue_init(&req->wait_queue);
>      QLIST_INSERT_HEAD(&job->inflight_reqs, req, list);
>  }
> @@ -114,8 +114,10 @@ static int coroutine_fn backup_do_cow(BackupBlockJob 
> *job,
>                                sector_num * BDRV_SECTOR_SIZE,
>                                nb_sectors * BDRV_SECTOR_SIZE);
> 
> -    wait_for_overlapping_requests(job, start, end);
> -    cow_request_begin(&cow_request, job, start, end);
> +    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);
> 
>      for (; start < end; start++) {
>          if (test_bit(start, job->done_bitmap)) {
> @@ -277,32 +279,29 @@ void backup_do_checkpoint(BlockJob *job, Error **errp)
>      bitmap_zero(backup_job->done_bitmap, len);
>  }
> 
> -void backup_wait_for_overlapping_requests(BlockJob *job, int64_t sector_num,
> -                                          int nb_sectors)
> +void backup_wait_for_overlapping_requests(BlockJob *job, int64_t offset,
> +                                          uint64_t bytes)
>  {
>      BackupBlockJob *backup_job = container_of(job, BackupBlockJob, common);
> -    int64_t sectors_per_cluster = cluster_size_sectors(backup_job);
>      int64_t start, end;
> 
>      assert(job->driver->job_type == BLOCK_JOB_TYPE_BACKUP);
> 
> -    start = sector_num / sectors_per_cluster;
> -    end = DIV_ROUND_UP(sector_num + nb_sectors, sectors_per_cluster);
> +    start = QEMU_ALIGN_DOWN(offset, backup_job->cluster_size);
> +    end = QEMU_ALIGN_UP(offset + bytes, backup_job->cluster_size);
>      wait_for_overlapping_requests(backup_job, start, end);
>  }
> 
>  void backup_cow_request_begin(CowRequest *req, BlockJob *job,
> -                              int64_t sector_num,
> -                              int nb_sectors)
> +                              int64_t offset, uint64_t bytes)
>  {
>      BackupBlockJob *backup_job = container_of(job, BackupBlockJob, common);
> -    int64_t sectors_per_cluster = cluster_size_sectors(backup_job);
>      int64_t start, end;
> 
>      assert(job->driver->job_type == BLOCK_JOB_TYPE_BACKUP);
> 
> -    start = sector_num / sectors_per_cluster;
> -    end = DIV_ROUND_UP(sector_num + nb_sectors, sectors_per_cluster);
> +    start = QEMU_ALIGN_DOWN(offset, backup_job->cluster_size);
> +    end = QEMU_ALIGN_UP(offset + bytes, backup_job->cluster_size);
>      cow_request_begin(req, backup_job, start, end);
>  }
> 
> diff --git a/block/replication.c b/block/replication.c
> index 3885f04..8f3aba7 100644
> --- a/block/replication.c
> +++ b/block/replication.c
> @@ -234,10 +234,14 @@ static coroutine_fn int 
> replication_co_readv(BlockDriverState *bs,
>      }
> 
>      if (job) {
> -        backup_wait_for_overlapping_requests(child->bs->job, sector_num,
> -                                             remaining_sectors);
> -        backup_cow_request_begin(&req, child->bs->job, sector_num,
> -                                 remaining_sectors);
> +        uint64_t remaining_bytes = remaining_sectors * BDRV_SECTOR_SIZE;
> +
> +        backup_wait_for_overlapping_requests(child->bs->job,
> +                                             sector_num * BDRV_SECTOR_SIZE,
> +                                             remaining_bytes);
> +        backup_cow_request_begin(&req, child->bs->job,
> +                                 sector_num * BDRV_SECTOR_SIZE,
> +                                 remaining_bytes);
>          ret = bdrv_co_readv(bs->file, sector_num, remaining_sectors,
>                              qiov);
>          backup_cow_request_end(&req);
> -- 
> 2.9.4
>