[Xen-devel] [PATCH] xen/balloon: Avoid OOM when requesting highmem

[Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>]

If highmem pages are requested from the balloon on a system without
highmem, the implementation of alloc_xenballooned_pages will allocate
all available memory trying to find highmem pages to return. Allow
low memory to be returned when highmem pages are requested to avoid
this loop.

Signed-off-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
---
 drivers/xen/balloon.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index d01944e..1a23033 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -500,7 +500,7 @@ 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
- * @highmem: highmem or lowmem pages
+ * @highmem: allow highmem pages
  * @return 0 on success, error otherwise
  */
 int alloc_xenballooned_pages(int nr_pages, struct page **pages, bool highmem)
@@ -510,7 +510,7 @@ int alloc_xenballooned_pages(int nr_pages, struct page 
**pages, bool highmem)
        mutex_lock(&balloon_mutex);
        while (pgno < nr_pages) {
                page = balloon_retrieve(highmem);
-               if (page && PageHighMem(page) == highmem) {
+               if (page && (highmem || !PageHighMem(page))) {
                        pages[pgno++] = page;
                } else {
                        enum bp_state st;
-- 
1.7.6.4


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