Re: [Qemu-devel] [PATCH v3 10/29] block: Introduce bdrv_co_do_preadv()

["Benoît Canet" <benoit.canet@irqsave.net>]

Le Friday 17 Jan 2014 à 15:15:00 (+0100), Kevin Wolf a écrit :
> Similar to bdrv_pread(), which aligns byte-aligned request to 512 byte
> sectors, bdrv_co_do_preadv() takes a byte-aligned request and aligns it
> to the alignment specified in bs->request_alignment.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++------
>  1 file changed, 58 insertions(+), 6 deletions(-)
> 
> diff --git a/block.c b/block.c
> index 0c2baf5..f378a10 100644
> --- a/block.c
> +++ b/block.c
> @@ -2791,17 +2791,23 @@ out:
>  /*
>   * Handle a read request in coroutine context
>   */
> -static int coroutine_fn bdrv_co_do_readv(BlockDriverState *bs,
> -    int64_t sector_num, int nb_sectors, QEMUIOVector *qiov,
> +static int coroutine_fn bdrv_co_do_preadv(BlockDriverState *bs,
> +    int64_t offset, unsigned int bytes, QEMUIOVector *qiov,
>      BdrvRequestFlags flags)
>  {
>      BlockDriver *drv = bs->drv;
> +    /* TODO Lift BDRV_SECTOR_SIZE restriction in BlockDriver interface */
> +    uint64_t align = MAX(BDRV_SECTOR_SIZE, bs->request_alignment);
> +    uint8_t *head_buf = NULL;
> +    uint8_t *tail_buf = NULL;
> +    QEMUIOVector local_qiov;
> +    bool use_local_qiov = false;
>      int ret;
>  
>      if (!drv) {
>          return -ENOMEDIUM;
>      }
> -    if (bdrv_check_request(bs, sector_num, nb_sectors)) {
> +    if (bdrv_check_byte_request(bs, offset, bytes)) {
>          return -EIO;
>      }
>  
> @@ -2811,14 +2817,60 @@ static int coroutine_fn bdrv_co_do_readv(BlockDriverState *bs,
>  
>      /* throttling disk I/O */
>      if (bs->io_limits_enabled) {
> -        bdrv_io_limits_intercept(bs, nb_sectors, false);
> +        /* TODO Switch to byte granularity */
> +        bdrv_io_limits_intercept(bs, bytes >> BDRV_SECTOR_BITS, false);
> +    }
> +
> +    /* Align read if necessary by padding qiov */
> +    if (offset & (align - 1)) {
> +        head_buf = qemu_blockalign(bs, align);
> +        qemu_iovec_init(&local_qiov, qiov->niov + 2);
> +        qemu_iovec_add(&local_qiov, head_buf, offset & (align - 1));
> +        qemu_iovec_concat(&local_qiov, qiov, 0, qiov->size);
> +        use_local_qiov = true;
> +
> +        bytes += offset & (align - 1);
> +        offset = offset & ~(align - 1);
> +    }
> +
> +    if ((offset + bytes) & (align - 1)) {
> +        if (!use_local_qiov) {
> +            qemu_iovec_init(&local_qiov, qiov->niov + 1);
> +            qemu_iovec_concat(&local_qiov, qiov, 0, qiov->size);
> +            use_local_qiov = true;
> +        }
> +        tail_buf = qemu_blockalign(bs, align);
> +        qemu_iovec_add(&local_qiov, tail_buf,
> +                       align - ((offset + bytes) & (align - 1)));
> +
> +        bytes = ROUND_UP(bytes, align);
> +    }
> +
> +    ret = bdrv_aligned_preadv(bs, offset, bytes,
> +                              use_local_qiov ? &local_qiov : qiov,
> +                              flags);
> +
> +    if (use_local_qiov) {
> +        qemu_iovec_destroy(&local_qiov);
> +        qemu_vfree(head_buf);
> +        qemu_vfree(tail_buf);
>      }
>  
> -    ret = bdrv_aligned_preadv(bs, sector_num << BDRV_SECTOR_BITS,
> -                             nb_sectors << BDRV_SECTOR_BITS, qiov, flags);
>      return ret;
>  }
>  
> +static int coroutine_fn bdrv_co_do_readv(BlockDriverState *bs,
> +    int64_t sector_num, int nb_sectors, QEMUIOVector *qiov,
> +    BdrvRequestFlags flags)
> +{
> +    if (nb_sectors < 0 || nb_sectors > (UINT_MAX >> BDRV_SECTOR_BITS)) {
> +        return -EINVAL;
> +    }
> +
> +    return bdrv_co_do_preadv(bs, sector_num << BDRV_SECTOR_BITS,
> +                             nb_sectors << BDRV_SECTOR_BITS, qiov, flags);
> +}
> +
>  int coroutine_fn bdrv_co_readv(BlockDriverState *bs, int64_t sector_num,
>      int nb_sectors, QEMUIOVector *qiov)
>  {
> -- 
> 1.8.1.4
> 
> 

Reviewed-by: Benoit Canet <benoit@irqsave.net>