Re: [Qemu-devel] [PATCH v2 16/24] block: Make zero-after-EOF work with larger alignment

[Max Reitz]

On 13.12.2013 14:22, Kevin Wolf wrote:
> Odd file sizes could make bdrv_aligned_preadv() shorten the request in
> non-aligned ways. Fix it by rounding to the required alignment instead
> of 512 bytes.
>
> Signed-off-by: Kevin Wolf <address@hidden>
> ---
>   block.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/block.c b/block.c
> index b4f6ead..6dddb7c 100644
> --- a/block.c
> +++ b/block.c
> @@ -2725,7 +2725,7 @@ err:
>    */
>   static int coroutine_fn bdrv_aligned_preadv(BlockDriverState *bs,
>       BdrvTrackedRequest *req, int64_t offset, unsigned int bytes,
> -    QEMUIOVector *qiov, int flags)
> +    int64_t align, QEMUIOVector *qiov, int flags)
>   {
>       BlockDriver *drv = bs->drv;
>       int ret;
> @@ -2773,7 +2773,7 @@ static int coroutine_fn 
> bdrv_aligned_preadv(BlockDriverState *bs,
>           }
>   
>           total_sectors = DIV_ROUND_UP(len, BDRV_SECTOR_SIZE);
> -        max_nb_sectors = MAX(0, total_sectors - sector_num);
> +        max_nb_sectors = MAX(0, ROUND_UP(total_sectors - sector_num, align));

It appears this should be an alignment given in sectors…

>           if (max_nb_sectors > 0) {
>               ret = drv->bdrv_co_readv(bs, sector_num,
>                                        MIN(nb_sectors, max_nb_sectors), qiov);
> @@ -2858,7 +2858,7 @@ static int coroutine_fn 
> bdrv_co_do_preadv(BlockDriverState *bs,
>       }
>   
>       tracked_request_begin(&req, bs, offset, bytes, false);
> -    ret = bdrv_aligned_preadv(bs, &req, offset, bytes,
> +    ret = bdrv_aligned_preadv(bs, &req, offset, bytes, align,

Whereas this one is an alignment given in bytes.

Max

>                                 use_local_qiov ? &local_qiov : qiov,
>                                 flags);
>       tracked_request_end(&req);