Pages that have been ballooned are useful for other Xen drivers doing
grant table actions, because these pages have valid struct page/PFNs but
have no valid MFN so are available for remapping.
Signed-off-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
---
drivers/xen/balloon.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++++
include/xen/balloon.h | 3 ++
2 files changed, 63 insertions(+), 0 deletions(-)
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index b0a7a92..ec75f26 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -328,6 +328,66 @@ void balloon_set_new_target(unsigned long target)
}
EXPORT_SYMBOL_GPL(balloon_set_new_target);
+/**
+ * alloc_xenballooned_pages - get pages that have been ballooned out
+ * @nr_pages: Number of pages to get
+ * @pages: pages returned
+ * @return number of pages retrieved
+ */
+int alloc_xenballooned_pages(int nr_pages, struct page** pages)
+{
+ int rv = 0;
+ int alloc_failed = 0;
+ struct page* page;
+ mutex_lock(&balloon_mutex);
+ /* Pages are pulled off the back of the queue to prefer highmem */
+ while (rv < nr_pages) {
+ if (list_empty(&ballooned_pages)) {
+ if (alloc_failed)
+ break;
+ if (decrease_reservation(nr_pages - rv))
+ alloc_failed = 1;
+ } else {
+ page = list_entry(ballooned_pages.prev,
+ struct page, lru);
+ list_del(&page->lru);
+ pages[rv++] = page;
+ }
+ }
+ mutex_unlock(&balloon_mutex);
+ return rv;
+}
+EXPORT_SYMBOL(alloc_xenballooned_pages);
+
+/**
+ * free_xenballooned_pages - return pages retrieved with get_ballooned_pages
+ * @nr_pages: Number of pages
+ * @pages: pages to return
+ */
+void free_xenballooned_pages(int nr_pages, struct page** pages)
+{
+ int i;
+
+ mutex_lock(&balloon_mutex);
+
+ for (i = 0; i < nr_pages; i++) {
+ if (!pages[i])
+ continue;
+ if (PageHighMem(pages[i])) {
+ list_add_tail(&pages[i]->lru, &ballooned_pages);
+ } else {
+ list_add(&pages[i]->lru, &ballooned_pages);
+ }
+ }
+
+ /* The balloon may be too large now. Shrink it if needed. */
+ if (current_target() != balloon_stats.current_pages)
+ schedule_work(&balloon_worker);
+
+ mutex_unlock(&balloon_mutex);
+}
+EXPORT_SYMBOL(free_xenballooned_pages);
+
static int __init balloon_init(void)
{
unsigned long pfn, nr_pages, extra_pfn_end;
diff --git a/include/xen/balloon.h b/include/xen/balloon.h
index b2b7c21..72a6927 100644
--- a/include/xen/balloon.h
+++ b/include/xen/balloon.h
@@ -19,3 +19,6 @@ struct balloon_stats {
extern struct balloon_stats balloon_stats;
void balloon_set_new_target(unsigned long target);
+
+int alloc_xenballooned_pages(int nr_pages, struct page** pages);
+void free_xenballooned_pages(int nr_pages, struct page** pages);
--
1.7.3.4
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