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 <kw...@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 <ben...@irqsave.net>
