[PATCH] adjust gfp mask passed on nested vmalloc() invocation

[Jan Beulich]

- fix a latent bug resulting from blindly or-ing in __GFP_ZERO, since
  the combination of this and __GFP_HIGHMEM (possibly passed into the
  function) is forbidden in interrupt context
- avoid wasting more precious resources (DMA or DMA32 pools), when
  being called through vmalloc_32{,_user}()
- explicitly allow using high memory here even if the outer allocation
  request doesn't allow it, unless is collides with __GFP_ZERO

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>

---
 mm/vmalloc.c |   12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

--- linux-2.6.32-rc3/mm/vmalloc.c	2009-10-05 11:59:56.000000000 +0200
+++ 2.6.32-rc3-vmalloc-nested-gfp/mm/vmalloc.c	2009-10-05 08:40:36.000000000 +0200
@@ -1410,6 +1410,7 @@ static void *__vmalloc_area_node(struct 
 {
 	struct page **pages;
 	unsigned int nr_pages, array_size, i;
+	gfp_t nested_gfp = (gfp_mask & GFP_RECLAIM_MASK) | __GFP_ZERO;
 
 	nr_pages = (area->size - PAGE_SIZE) >> PAGE_SHIFT;
 	array_size = (nr_pages * sizeof(struct page *));
@@ -1417,13 +1418,16 @@ static void *__vmalloc_area_node(struct 
 	area->nr_pages = nr_pages;
 	/* Please note that the recursion is strictly bounded. */
 	if (array_size > PAGE_SIZE) {
-		pages = __vmalloc_node(array_size, gfp_mask | __GFP_ZERO,
+#ifdef CONFIG_HIGHMEM
+		/* See the comment in prep_zero_page(). */
+		if (!in_interrupt())
+			nested_gfp |= __GFP_HIGHMEM;
+#endif
+		pages = __vmalloc_node(array_size, nested_gfp,
 				PAGE_KERNEL, node, caller);
 		area->flags |= VM_VPAGES;
 	} else {
-		pages = kmalloc_node(array_size,
-				(gfp_mask & GFP_RECLAIM_MASK) | __GFP_ZERO,
-				node);
+		pages = kmalloc_node(array_size, nested_gfp, node);
 	}
 	area->pages = pages;
 	area->caller = caller;



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