Re: [PATCH] file-posix: split hdev_refresh_limits from raw_refresh_limits

[Tom Yan]

Oops I forgot max_transfer needs to be in bytes (and BLKSECTGET in sg
has always been implemented wrongly). Will send a new version.

On Fri, 4 Sep 2020 at 06:37, Tom Yan <tom.ty89@gmail.com> wrote:
>
> sg_get_max_transfer_length() and sg_get_max_segments() have nothing
> to do with the sg driver or SG_IO at all. They can be and should be
> used on all host devices / cdroms (on Linux).
>
> Also use MIN_NON_ZERO instead when we clamp max_sectors against
> max_segments.
>
> Signed-off-by: Tom Yan <tom.ty89@gmail.com>
> ---
>  block/file-posix.c | 39 ++++++++++++++++++++++-----------------
>  1 file changed, 22 insertions(+), 17 deletions(-)
>
> diff --git a/block/file-posix.c b/block/file-posix.c
> index 9a00d4190a..a38f43af4f 100644
> --- a/block/file-posix.c
> +++ b/block/file-posix.c
> @@ -1163,7 +1163,7 @@ static void raw_reopen_abort(BDRVReopenState *state)
>      s->reopen_state = NULL;
>  }
>
> -static int sg_get_max_transfer_length(int fd)
> +static int get_max_transfer_length(int fd)
>  {
>  #ifdef BLKSECTGET
>      int max_bytes = 0;
> @@ -1178,7 +1178,7 @@ static int sg_get_max_transfer_length(int fd)
>  #endif
>  }
>
> -static int sg_get_max_segments(int fd)
> +static int get_max_segments(int fd)
>  {
>  #ifdef CONFIG_LINUX
>      char buf[32];
> @@ -1233,23 +1233,28 @@ static void raw_refresh_limits(BlockDriverState *bs, 
> Error **errp)
>  {
>      BDRVRawState *s = bs->opaque;
>
> -    if (bs->sg) {
> -        int ret = sg_get_max_transfer_length(s->fd);
> +    raw_probe_alignment(bs, s->fd, errp);
> +    bs->bl.min_mem_alignment = s->buf_align;
> +    bs->bl.opt_mem_alignment = MAX(s->buf_align, qemu_real_host_page_size);
> +}
>
> -        if (ret > 0 && ret <= BDRV_REQUEST_MAX_BYTES) {
> -            bs->bl.max_transfer = pow2floor(ret);
> -        }
> +static void hdev_refresh_limits(BlockDriverState *bs, Error **errp)
> +{
> +    BDRVRawState *s = bs->opaque;
>
> -        ret = sg_get_max_segments(s->fd);
> -        if (ret > 0) {
> -            bs->bl.max_transfer = MIN(bs->bl.max_transfer,
> -                                      ret * qemu_real_host_page_size);
> -        }
> +    int ret = get_max_transfer_length(s->fd);
> +
> +    if (ret > 0 && ret <= BDRV_REQUEST_MAX_BYTES) {
> +        bs->bl.max_transfer = pow2floor(ret);
>      }
>
> -    raw_probe_alignment(bs, s->fd, errp);
> -    bs->bl.min_mem_alignment = s->buf_align;
> -    bs->bl.opt_mem_alignment = MAX(s->buf_align, qemu_real_host_page_size);
> +    ret = get_max_segments(s->fd);
> +    if (ret > 0) {
> +        bs->bl.max_transfer = MIN_NON_ZERO(bs->bl.max_transfer,
> +                                           ret * qemu_real_host_page_size);
> +    }
> +
> +    raw_refresh_limits(bs, errp);
>  }
>
>  static int check_for_dasd(int fd)
> @@ -3604,7 +3609,7 @@ static BlockDriver bdrv_host_device = {
>      .bdrv_co_pdiscard       = hdev_co_pdiscard,
>      .bdrv_co_copy_range_from = raw_co_copy_range_from,
>      .bdrv_co_copy_range_to  = raw_co_copy_range_to,
> -    .bdrv_refresh_limits = raw_refresh_limits,
> +    .bdrv_refresh_limits = hdev_refresh_limits,
>      .bdrv_io_plug = raw_aio_plug,
>      .bdrv_io_unplug = raw_aio_unplug,
>      .bdrv_attach_aio_context = raw_aio_attach_aio_context,
> @@ -3728,7 +3733,7 @@ static BlockDriver bdrv_host_cdrom = {
>      .bdrv_co_preadv         = raw_co_preadv,
>      .bdrv_co_pwritev        = raw_co_pwritev,
>      .bdrv_co_flush_to_disk  = raw_co_flush_to_disk,
> -    .bdrv_refresh_limits = raw_refresh_limits,
> +    .bdrv_refresh_limits = hdev_refresh_limits,
>      .bdrv_io_plug = raw_aio_plug,
>      .bdrv_io_unplug = raw_aio_unplug,
>      .bdrv_attach_aio_context = raw_aio_attach_aio_context,
> --
> 2.28.0
>