El 26/01/15 a les 18.01, David Vrabel ha escrit:
> From: Jennifer Herbert <jennifer.herb...@citrix.com>
>
> Use gnttab_unmap_refs_async() to wait until the mapped pages are no
> longer in use before unmapping them.
>
> This allows blkback to use network storage which may retain refs to
> pages in queued skbs after the block I/O has completed.
>
> Signed-off-by: Jennifer Herbert <jennifer.herb...@citrix.com>
> Signed-off-by: David Vrabel <david.vra...@citrix.com>
Acked-by: Roger Pau Monné <roger....@citrix.com>
This looks fine, only one comment below.
[...]
> +/*
> + * Unmap the grant references, and also remove the M2P over-rides
> + * used in the 'pending_req'.
> + */
> +static void xen_blkbk_unmap(struct xen_blkif *blkif,
> + struct grant_page *pages[],
> + int num)
> +{
> + struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
> + struct page *unmap_pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
> + unsigned int invcount = 0;
> + int ret;
> +
> + while (num) {
> + unsigned int batch = min(num, BLKIF_MAX_SEGMENTS_PER_REQUEST);
> +
> + invcount = xen_blkbk_unmap_prepare(blkif, pages, batch,
> + unmap, unmap_pages);
> + if (invcount) {
> + ret = gnttab_unmap_refs(unmap, NULL, unmap_pages,
> invcount);
> BUG_ON(ret);
> put_free_pages(blkif, unmap_pages, invcount);
> - invcount = 0;
> }
> - }
> - if (invcount) {
> - ret = gnttab_unmap_refs(unmap, NULL, unmap_pages, invcount);
> - BUG_ON(ret);
> - put_free_pages(blkif, unmap_pages, invcount);
> + pages += batch;
> + num -= batch;
Could you add a comment explaining that the loop is not optimal if the
pages array contains both persistent and non-persistent grants?
Roger.
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