On Wed, Nov 07, 2012 at 04:11:46PM -0800, Andrew Morton wrote: > On Thu, 08 Nov 2012 09:32:18 +1030 > Rusty Russell <rusty@xxxxxxxxxxxxxxx> wrote: > > > Rafael Aquini <aquini@xxxxxxxxxx> writes: > > > + * virtballoon_migratepage - perform the balloon page migration on behalf of > > > + * a compation thread. (called under page lock) > > > > > + if (!mutex_trylock(&vb->balloon_lock)) > > > + return -EAGAIN; > > > > Erk, OK... > > Not really. As is almost always the case with a trylock, it needs a > comment explaining why we couldn't use the far superior mutex_lock(). > Data: this reader doesn't know! > > > > + /* balloon's page migration 1st step -- inflate "newpage" */ > > > + spin_lock_irqsave(&vb_dev_info->pages_lock, flags); > > > + balloon_page_insert(newpage, mapping, &vb_dev_info->pages); > > > + vb_dev_info->isolated_pages--; > > > + spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags); > > > + vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE; > > > + set_page_pfns(vb->pfns, newpage); > > > + tell_host(vb, vb->inflate_vq); > > > > tell_host does wait_event(), so you can't call it under the page_lock. > > Right? > > Sleeping inside lock_page() is OK. More problematic is that GFP_KERNEL > allocation. Do you mean this one: if (virtqueue_add_buf(vq, &sg, 1, 0, vb, GFP_KERNEL) < 0) ? In practice it never triggers an allocation, we can pass in GFP_ATOMIC just as well. -- MST -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>