[Xen-devel] [PATCH] mm: Scrub pages returned back to heap if MEMF_no_scrub is set

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

Set free_heap_pages()'s need_scrub to true if alloc_domheap_pages()
returns pages back to heap as result of assign_pages() error when those
pages were requested with MEMF_no_scrub flag.

We need to do this because there is a possibility that
alloc_heap_pages() might clear buddy's PGC_need_scrubs flag without
actually clearing the page.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
---
We are declaring a likely clean (or almost clean) chunk to be dirty. Since
this only happend on assign_pages() error I figured it would be acceptable.

Alternatively, we could make alloc_heap_pages() return (via a parameter)
an indication whether anything was dirty.

 xen/common/page_alloc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index 86c0794..e88373d 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -2227,7 +2227,7 @@ struct page_info *alloc_domheap_pages(
     if ( d && !(memflags & MEMF_no_owner) &&
          assign_pages(d, pg, order, memflags) )
     {
-        free_heap_pages(pg, order, false);
+        free_heap_pages(pg, order, !!(memflags & MEMF_no_scrub));
         return NULL;
     }
     
-- 
1.8.3.1


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