Re: [PATCH v12 11/14] copy-on-read: add support for read flags to COR-filter

[Vladimir Sementsov-Ogievskiy]

22.10.2020 21:13, Andrey Shinkevich wrote:
> Add the BDRV_REQ_COPY_ON_READ and BDRV_REQ_PREFETCH flags to the
> supported_read_flags of the COR-filter.
>
> Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
> ---
>   block/copy-on-read.c | 2 ++
>   1 file changed, 2 insertions(+)
>
> diff --git a/block/copy-on-read.c b/block/copy-on-read.c
> index 8178a91..a2b180a 100644
> --- a/block/copy-on-read.c
> +++ b/block/copy-on-read.c
> @@ -50,6 +50,8 @@ static int cor_open(BlockDriverState *bs, QDict *options, int 
> flags,
>           return -EINVAL;
>       }
>   
> +    bs->supported_read_flags = BDRV_REQ_COPY_ON_READ | BDRV_REQ_PREFETCH;
> +
>       bs->supported_write_flags = BDRV_REQ_WRITE_UNCHANGED |
>           (BDRV_REQ_FUA & bs->file->bs->supported_write_flags);
>   

This should be merged with the following patch, otherwise it doesn't make 
sense. You mark filter as supporting PREFETCH, but actually it just ignores it 
(and may crash on trying to read into qiov=NULL).

--
Best regards,
Vladimir