Re: [Qemu-devel] [PATCH for 2.6 1/3] backup: Use Bitmap to replace "s->bitmap"

[John Snow]

On 11/20/2015 04:59 AM, Fam Zheng wrote:
> "s->bitmap" tracks done sectors, we only check bit states without using any
> iterator which HBitmap is good for. Switch to "Bitmap" which is simpler and
> more memory efficient.
> 
> Meanwhile, rename it to done_bitmap, to reflect the intention.
> 
> Signed-off-by: Fam Zheng <address@hidden>
> ---
>  block/backup.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/block/backup.c b/block/backup.c
> index 3b39119..d408f98 100644
> --- a/block/backup.c
> +++ b/block/backup.c
> @@ -22,6 +22,7 @@
>  #include "qapi/qmp/qerror.h"
>  #include "qemu/ratelimit.h"
>  #include "sysemu/block-backend.h"
> +#include "qemu/bitmap.h"
>  
>  #define BACKUP_CLUSTER_BITS 16
>  #define BACKUP_CLUSTER_SIZE (1 << BACKUP_CLUSTER_BITS)
> @@ -47,7 +48,7 @@ typedef struct BackupBlockJob {
>      BlockdevOnError on_target_error;
>      CoRwlock flush_rwlock;
>      uint64_t sectors_read;
> -    HBitmap *bitmap;
> +    unsigned long *done_bitmap;
>      QLIST_HEAD(, CowRequest) inflight_reqs;
>  } BackupBlockJob;
>  
> @@ -113,7 +114,7 @@ static int coroutine_fn backup_do_cow(BlockDriverState 
> *bs,
>      cow_request_begin(&cow_request, job, start, end);
>  
>      for (; start < end; start++) {
> -        if (hbitmap_get(job->bitmap, start)) {
> +        if (test_bit(start, job->done_bitmap)) {
>              trace_backup_do_cow_skip(job, start);
>              continue; /* already copied */
>          }
> @@ -164,7 +165,7 @@ static int coroutine_fn backup_do_cow(BlockDriverState 
> *bs,
>              goto out;
>          }
>  
> -        hbitmap_set(job->bitmap, start, 1);
> +        bitmap_set(job->done_bitmap, start, 1);
>  
>          /* 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.
> @@ -394,7 +395,7 @@ static void coroutine_fn backup_run(void *opaque)
>      start = 0;
>      end = DIV_ROUND_UP(job->common.len, BACKUP_CLUSTER_SIZE);
>  
> -    job->bitmap = hbitmap_alloc(end, 0);
> +    job->done_bitmap = bitmap_new(end);
>  
>      bdrv_set_enable_write_cache(target, true);
>      if (target->blk) {
> @@ -475,7 +476,7 @@ static void coroutine_fn backup_run(void *opaque)
>      /* wait until pending backup_do_cow() calls have completed */
>      qemu_co_rwlock_wrlock(&job->flush_rwlock);
>      qemu_co_rwlock_unlock(&job->flush_rwlock);
> -    hbitmap_free(job->bitmap);
> +    g_free(job->done_bitmap);
>  
>      if (target->blk) {
>          blk_iostatus_disable(target->blk);
> 

Replacing the bitmap_set with set_bit, in response to Paolo's comment:

Reviewed-by: John Snow <address@hidden>