On Thu, Jul 18, 2019 at 05:27:20PM +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.
> This is necessary when it's used from balloon_page_enqueue_list, but
> not from balloon_page_enqueue_one.
>
> So remove the list_del balloon_page_enqueue_one, and update some
> comments as a reminder.
>
> Signed-off-by: Wei Wang <wei.w.wang@xxxxxxxxx>
ok I posted v3 with typo fixes. 1/2 is this patch with comment changes. Pls take a look.
> ---
> ChangeLong:
> v1->v2: updated some comments
>
> mm/balloon_compaction.c | 14 ++++++++++----
> 1 file changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c
> index 83a7b61..8639bfc 100644
> --- a/mm/balloon_compaction.c
> +++ b/mm/balloon_compaction.c
> @@ -21,7 +21,6 @@ static void balloon_page_enqueue_one(struct balloon_dev_info *b_dev_info,
> * memory corruption is possible and we should stop execution.
> */
> BUG_ON(!trylock_page(page));
> - list_del(&page->lru);
> balloon_page_insert(b_dev_info, page);
> unlock_page(page);
> __count_vm_event(BALLOON_INFLATE);
> @@ -33,7 +32,7 @@ static void balloon_page_enqueue_one(struct balloon_dev_info *b_dev_info,
> * @b_dev_info: balloon device descriptor where we will insert a new page to
> * @pages: pages to enqueue - allocated using balloon_page_alloc.
> *
> - * Driver must call it to properly enqueue a balloon pages before definitively
> + * Driver must call it to properly enqueue balloon pages before definitively
> * removing it from the guest system.
> *
> * Return: number of pages that were enqueued.
> @@ -47,6 +46,7 @@ size_t balloon_page_list_enqueue(struct balloon_dev_info *b_dev_info,
>
> spin_lock_irqsave(&b_dev_info->pages_lock, flags);
> list_for_each_entry_safe(page, tmp, pages, lru) {
> + list_del(&page->lru);
> balloon_page_enqueue_one(b_dev_info, page);
> n_pages++;
> }
> @@ -128,13 +128,19 @@ struct page *balloon_page_alloc(void)
> EXPORT_SYMBOL_GPL(balloon_page_alloc);
>
> /*
> - * balloon_page_enqueue - allocates a new page and inserts it into the balloon
> - * page list.
> + * balloon_page_enqueue - inserts a new page into the balloon page list.
> + *
> * @b_dev_info: balloon device descriptor where we will insert a new page to
> * @page: new page to enqueue - allocated using balloon_page_alloc.
> *
> * Driver must call it to properly enqueue a new allocated balloon page
> * before definitively removing it from the guest system.
> + *
> + * Drivers must not call balloon_page_enqueue on pages that have been
> + * pushed to a list with balloon_page_push before removing them with
> + * balloon_page_pop. To all pages on a list, use balloon_page_list_enqueue
> + * instead.
> + *
> * This function returns the page address for the recently enqueued page or
> * NULL in the case we fail to allocate a new page this turn.
> */
> --
> 2.7.4
