Re: [PATCH v5 11/12] blkio: implement BDRV_REQ_REGISTERED_BUF optimization

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Tue, Sep 27, 2022 at 03:34:30PM -0400, Stefan Hajnoczi wrote:
> +    ret = blkio_get_bool(s->blkio,
> +                         "mem-regions-pinned",
> +                         &s->mem_regions_pinned);
> +    if (ret < 0) {
> +        /* Be conservative (assume pinning) if the property is not supported */
> +        s->mem_regions_pinned = true;

This is too conservative :). It can be changed to:

  s->mem_regions_pinned = s->needs_mem_regions;

That way we avoid ram_block_discard_disable() for libblkio drivers (like
io_uring in libblkio 1.0) that don't use memory regions and don't
support the "mem-regions-pinned" property yet.

Stefan

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