From 64b4a954b03a1153fb8ae38d6ffbd991e01a1e80 Mon Sep 17 00:00:00 2001
From: Christoph Lameter <clameter@engr.sgi.com>
Date: Sat, 4 Feb 2006 23:27:55 -0800
Subject: [PATCH] [PATCH] hugetlb: add comment explaining reasons for Bus
Errors
I just spent some time researching a Bus Error. Turns out that the huge
page fault handler can return VM_FAULT_SIGBUS for various conditions where
no huge page is available.
Add a note explaining the reasoning in the source.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Acked-by: William Lee Irwin III <wli@holomorphy.com>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---
mm/hugetlb.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index b21d78c941b52..ceb3ebb3c399e 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -444,6 +444,15 @@ int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
page = alloc_huge_page(vma, address);
if (!page) {
hugetlb_put_quota(mapping);
+ /*
+ * No huge pages available. So this is an OOM
+ * condition but we do not want to trigger the OOM
+ * killer, so we return VM_FAULT_SIGBUS.
+ *
+ * A program using hugepages may fault with Bus Error
+ * because no huge pages are available in the cpuset, per
+ * memory policy or because all are in use!
+ */
goto out;
}
--
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