Commit dd422906 authored by Wei Wang's avatar Wei Wang Committed by Michael S. Tsirkin
Browse files

mm/balloon_compaction: avoid duplicate page removal 



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.

Move list_del to balloon_page_enqueue, and update comments accordingly.

Fixes: 418a3ab1 (mm/balloon_compaction: List interfaces)
Signed-off-by: default avatarWei Wang <wei.w.wang@intel.com>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent 5f9e832c

mm/balloon_compaction.c

+9 −3
Original line number Diff line number Diff line
@@ -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);
@@ -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.

 */

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