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    SubjectRe: [PATCH v17 4/6] virtio-balloon: VIRTIO_BALLOON_F_SG
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    Wei Wang wrote:
    > @@ -164,6 +284,8 @@ static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
    > break;
    > }
    >
    > + if (use_sg && xb_set_page(vb, page, &pfn_min, &pfn_max) < 0)

    Isn't this leaking "page" ?

    > + break;
    > balloon_page_push(&pages, page);
    > }
    >



    > @@ -184,8 +307,12 @@ static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
    >
    > num_allocated_pages = vb->num_pfns;
    > /* Did we get any? */
    > - if (vb->num_pfns != 0)
    > - tell_host(vb, vb->inflate_vq);
    > + if (vb->num_pfns) {
    > + if (use_sg)
    > + tell_host_sgs(vb, vb->inflate_vq, pfn_min, pfn_max);

    Please describe why tell_host_sgs() can work without __GFP_DIRECT_RECLAIM allocation,
    for tell_host_sgs() is called with vb->balloon_lock mutex held.

    > + else
    > + tell_host(vb, vb->inflate_vq);
    > + }
    > mutex_unlock(&vb->balloon_lock);
    >
    > return num_allocated_pages;



    > @@ -223,7 +353,13 @@ static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
    > page = balloon_page_dequeue(vb_dev_info);
    > if (!page)
    > break;
    > - set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
    > + if (use_sg) {
    > + if (xb_set_page(vb, page, &pfn_min, &pfn_max) < 0)

    Isn't this leaking "page" ?

    If this is inside vb->balloon_lock mutex (isn't this?), xb_set_page() must not
    use __GFP_DIRECT_RECLAIM allocation, for leak_balloon_sg_oom() will be blocked
    on vb->balloon_lock mutex.

    > + break;
    > + } else {
    > + set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
    > + }
    > +
    > list_add(&page->lru, &pages);
    > vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
    > }

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