On Thu, Jul 18, 2019 at 02:31:14PM +0800, Wei Wang wrote: > On 07/18/2019 12:31 PM, Michael S. Tsirkin wrote: > > On Thu, Jul 18, 2019 at 10:23:30AM +0800, Wei Wang wrote: > > > Fixes: 418a3ab1e778 (mm/balloon_compaction: List interfaces) > > > > > > A #GP is reported in the guest when requesting balloon inflation via > > > virtio-balloon. The reason is that the virtio-balloon driver has > > > removed the page from its internal page list (via balloon_page_pop), > > > but balloon_page_enqueue_one also calls "list_del" to do the removal. > > I would add here "this is necessary when it's used from > > balloon_page_enqueue_list but not when it's called > > from balloon_page_enqueue". > > > > > So remove the list_del in balloon_page_enqueue_one, and have the callers > > > do the page removal from their own page lists. > > > > > > Signed-off-by: Wei Wang <wei.w.wang@xxxxxxxxx> > > Patch is good but comments need some work. > > > > > --- > > > mm/balloon_compaction.c | 3 ++- > > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > > > diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c > > > index 83a7b61..1a5ddc4 100644 > > > --- a/mm/balloon_compaction.c > > > +++ b/mm/balloon_compaction.c > > > @@ -11,6 +11,7 @@ > > > #include <linux/export.h> > > > #include <linux/balloon_compaction.h> > > > +/* Callers ensure that @page has been removed from its original list. */ > > This comment does not make sense. E.g. balloon_page_enqueue > > does nothing to ensure this. And drivers are not supposed > > to care how the page lists are managed. Pls drop. > > > > Instead please add the following to balloon_page_enqueue: > > > > > > Note: drivers must not call balloon_page_list_enqueue on > > Probably, you meant balloon_page_enqueue here. yes > The description for balloon_page_enqueue also seems incorrect: > "allocates a new page and inserts it into the balloon page list." > This function doesn't do any allocation itself. > Plan to reword it: inserts a new page into the balloon page list." And maybe " Page must have been allocated with balloon_page_alloc.". Also * Driver must call it to properly enqueue a balloon pages before definitively should be * Driver must call it to properly enqueue balloon pages before definitively > > Best, > Wei
