Re: [Qemu-devel] [PATCHv4 05/11] allow qemu_iovec_from_buffer() to specify offset from which to start copying

[Anthony Liguori <anthony@codemonkey.ws>]

On 03/15/2012 04:00 PM, Michael Tokarev wrote:
> Similar to
>   qemu_iovec_memset(QEMUIOVector *qiov, size_t offset,
>                     int c, size_t bytes);
> the new prototype is:
>   qemu_iovec_from_buf(QEMUIOVector *qiov, size_t offset,
>                       const void *buf, size_t bytes);
>
> The processing starts at offset bytes within qiov.
>
> This way, we may copy a bounce buffer directly to
> a middle of qiov.
>
> This is exactly the same function as iov_from_buf() from
> iov.c, so use the existing implementation and rename it
> to qemu_iovec_from_buf() to be shorter and to match the
> utility function.
>
> As with utility implementation, we now assert that the
> offset is inside actual iovec.  Nothing changed for
> current callers, because `offset' parameter is new.
>
> While at it, stop using "bounce-qiov" in block/qcow2.c
> and copy decrypted data directly from cluster_data
> instead of recreating a temp qiov for doing that
> (Cc'ing kwolf for this change).
>
> Signed-off-by: Michael Tokarev<mjt@tls.msk.ru>
> Cc: Kevin Wolf<kwolf@redhat.com>

Kevin, please Ack.

Regards,

Anthony Liguori

> ---
>   block.c       |    6 +++---
>   block/curl.c  |    6 +++---
>   block/qcow.c  |    2 +-
>   block/qcow2.c |    9 +++------
>   block/vdi.c   |    2 +-
>   cutils.c      |   16 +++-------------
>   qemu-common.h |    3 ++-
>   7 files changed, 16 insertions(+), 28 deletions(-)
>
> diff --git a/block.c b/block.c
> index b88ee90..b8db395 100644
> --- a/block.c
> +++ b/block.c
> @@ -1696,8 +1696,8 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BlockDriverState *bs,
>       }
>
>       skip_bytes = (sector_num - cluster_sector_num) * BDRV_SECTOR_SIZE;
> -    qemu_iovec_from_buffer(qiov, bounce_buffer + skip_bytes,
> -                           nb_sectors * BDRV_SECTOR_SIZE);
> +    qemu_iovec_from_buf(qiov, 0, bounce_buffer + skip_bytes,
> +                        nb_sectors * BDRV_SECTOR_SIZE);
>
>   err:
>       qemu_vfree(bounce_buffer);
> @@ -3244,7 +3244,7 @@ static void bdrv_aio_bh_cb(void *opaque)
>       BlockDriverAIOCBSync *acb = opaque;
>
>       if (!acb->is_write)
> -        qemu_iovec_from_buffer(acb->qiov, acb->bounce, acb->qiov->size);
> +        qemu_iovec_from_buf(acb->qiov, 0, acb->bounce, acb->qiov->size);
>       qemu_vfree(acb->bounce);
>       acb->common.cb(acb->common.opaque, acb->ret);
>       qemu_bh_delete(acb->bh);
> diff --git a/block/curl.c b/block/curl.c
> index e9102e3..cfc2ced 100644
> --- a/block/curl.c
> +++ b/block/curl.c
> @@ -142,8 +142,8 @@ static size_t curl_read_cb(void *ptr, size_t size, size_t nmemb, void *opaque)
>               continue;
>
>           if ((s->buf_off>= acb->end)) {
> -            qemu_iovec_from_buffer(acb->qiov, s->orig_buf + acb->start,
> -                                   acb->end - acb->start);
> +            qemu_iovec_from_buf(acb->qiov, 0, s->orig_buf + acb->start,
> +                                acb->end - acb->start);
>               acb->common.cb(acb->common.opaque, 0);
>               qemu_aio_release(acb);
>               s->acb[i] = NULL;
> @@ -178,7 +178,7 @@ static int curl_find_buf(BDRVCURLState *s, size_t start, size_t len,
>           {
>               char *buf = state->orig_buf + (start - state->buf_start);
>
> -            qemu_iovec_from_buffer(acb->qiov, buf, len);
> +            qemu_iovec_from_buf(acb->qiov, 0, buf, len);
>               acb->common.cb(acb->common.opaque, 0);
>
>               return FIND_RET_OK;
> diff --git a/block/qcow.c b/block/qcow.c
> index b1cfe1f..562a19c 100644
> --- a/block/qcow.c
> +++ b/block/qcow.c
> @@ -540,7 +540,7 @@ done:
>       qemu_co_mutex_unlock(&s->lock);
>
>       if (qiov->niov>  1) {
> -        qemu_iovec_from_buffer(qiov, orig_buf, qiov->size);
> +        qemu_iovec_from_buf(qiov, 0, orig_buf, qiov->size);
>           qemu_vfree(orig_buf);
>       }
>
> diff --git a/block/qcow2.c b/block/qcow2.c
> index 941a6a9..a24c0dc 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c
> @@ -476,7 +476,7 @@ static coroutine_fn int qcow2_co_readv(BlockDriverState *bs, int64_t sector_num,
>                   goto fail;
>               }
>
> -            qemu_iovec_from_buffer(&hd_qiov,
> +            qemu_iovec_from_buf(&hd_qiov, 0,
>                   s->cluster_cache + index_in_cluster * 512,
>                   512 * cur_nr_sectors);
>           } else {
> @@ -514,11 +514,8 @@ static coroutine_fn int qcow2_co_readv(BlockDriverState *bs, int64_t sector_num,
>               if (s->crypt_method) {
>                   qcow2_encrypt_sectors(s, sector_num,  cluster_data,
>                       cluster_data, cur_nr_sectors, 0,&s->aes_decrypt_key);
> -                qemu_iovec_reset(&hd_qiov);
> -                qemu_iovec_copy(&hd_qiov, qiov, bytes_done,
> -                    cur_nr_sectors * 512);
> -                qemu_iovec_from_buffer(&hd_qiov, cluster_data,
> -                    512 * cur_nr_sectors);
> +                qemu_iovec_from_buf(qiov, bytes_done,
> +                    cluster_data, 512 * cur_nr_sectors);
>               }
>           }
>
> diff --git a/block/vdi.c b/block/vdi.c
> index 6a0011f..24f4027 100644
> --- a/block/vdi.c
> +++ b/block/vdi.c
> @@ -635,7 +635,7 @@ static void vdi_aio_read_cb(void *opaque, int ret)
>       return;
>   done:
>       if (acb->qiov->niov>  1) {
> -        qemu_iovec_from_buffer(acb->qiov, acb->orig_buf, acb->qiov->size);
> +        qemu_iovec_from_buf(acb->qiov, 0, acb->orig_buf, acb->qiov->size);
>           qemu_vfree(acb->orig_buf);
>       }
>       acb->common.cb(acb->common.opaque, ret);
> diff --git a/cutils.c b/cutils.c
> index 0ddf4c7..b4dd844 100644
> --- a/cutils.c
> +++ b/cutils.c
> @@ -245,20 +245,10 @@ void qemu_iovec_to_buffer(QEMUIOVector *qiov, void *buf)
>       }
>   }
>
> -void qemu_iovec_from_buffer(QEMUIOVector *qiov, const void *buf, size_t count)
> +size_t qemu_iovec_from_buf(QEMUIOVector *qiov, size_t offset,
> +                           const void *buf, size_t bytes)
>   {
> -    const uint8_t *p = (const uint8_t *)buf;
> -    size_t copy;
> -    int i;
> -
> -    for (i = 0; i<  qiov->niov&&  count; ++i) {
> -        copy = count;
> -        if (copy>  qiov->iov[i].iov_len)
> -            copy = qiov->iov[i].iov_len;
> -        memcpy(qiov->iov[i].iov_base, p, copy);
> -        p     += copy;
> -        count -= copy;
> -    }
> +    return iov_from_buf(qiov->iov, qiov->niov, offset, buf, bytes);
>   }
>
>   size_t qemu_iovec_memset(QEMUIOVector *qiov, size_t offset,
> diff --git a/qemu-common.h b/qemu-common.h
> index 3c556c8..a179afe 100644
> --- a/qemu-common.h
> +++ b/qemu-common.h
> @@ -343,7 +343,8 @@ void qemu_iovec_concat(QEMUIOVector *dst, QEMUIOVector *src, size_t size);
>   void qemu_iovec_destroy(QEMUIOVector *qiov);
>   void qemu_iovec_reset(QEMUIOVector *qiov);
>   void qemu_iovec_to_buffer(QEMUIOVector *qiov, void *buf);
> -void qemu_iovec_from_buffer(QEMUIOVector *qiov, const void *buf, size_t count);
> +size_t qemu_iovec_from_buf(QEMUIOVector *qiov, size_t offset,
> +                           const void *buf, size_t bytes);
>   size_t qemu_iovec_memset(QEMUIOVector *qiov, size_t offset,
>                            int fillc, size_t bytes);
>