Re: [PATCH v3 6/7] migration/block-dirty-bitmap: add_bitmaps_to_list: check disk name once

[Eric Blake]

On 5/15/20 7:40 AM, Vladimir Sementsov-Ogievskiy wrote:
> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> Reviewed-by: Andrey Shinkevich <address@hidden>
> ---
>   migration/block-dirty-bitmap.c | 17 +++++++++++------
>   1 file changed, 11 insertions(+), 6 deletions(-)
>
> diff --git a/migration/block-dirty-bitmap.c b/migration/block-dirty-bitmap.c
> index 5d3a7d2b07..e0e081ce60 100644
> --- a/migration/block-dirty-bitmap.c
> +++ b/migration/block-dirty-bitmap.c
> @@ -274,17 +274,22 @@ static int add_bitmaps_to_list(BlockDriverState *bs, 
> const char *bs_name)
>       DirtyBitmapMigBitmapState *dbms;
>       Error *local_err = NULL;
>   
> +    bitmap = bdrv_dirty_bitmap_first(bs);
> +    if (!bitmap) {
> +        return 0;
> +    }
> +
> +    if (!bs_name || strcmp(bs_name, "") == 0) {
> +        error_report("Found bitmap '%s' in unnamed node %p. It can't "
> +                     "be migrated", bdrv_dirty_bitmap_name(bitmap), bs);

The %p is unusual; it does not help the end user, but only a developer 
with gdb access.

Maybe we could compress to:

"Bitmap '%s' in unnamed node can't be migrated"

> +        return -1;
> +    }
> +
>       FOR_EACH_DIRTY_BITMAP(bs, bitmap) {
>           if (!bdrv_dirty_bitmap_name(bitmap)) {
>               continue;
>           }
>   
> -        if (!bs_name || strcmp(bs_name, "") == 0) {
> -            error_report("Found bitmap '%s' in unnamed node %p. It can't "
> -                         "be migrated", bdrv_dirty_bitmap_name(bitmap), bs);
> -            return -1;
> -        }
> -

But since this is just code motion (hoisting an check outside of a loop, 
for fewer executions of something that does not change within the loop), 
it doesn't matter whether this patch goes in as-is or if you also tweak 
the error message.

Reviewed-by: Eric Blake <address@hidden>

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
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