[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>
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@ -444,6 +444,15 @@ retry:
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page = alloc_huge_page(vma, address);
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if (!page) {
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hugetlb_put_quota(mapping);
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/*
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* No huge pages available. So this is an OOM
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* condition but we do not want to trigger the OOM
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* killer, so we return VM_FAULT_SIGBUS.
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*
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* A program using hugepages may fault with Bus Error
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* because no huge pages are available in the cpuset, per
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* memory policy or because all are in use!
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*/
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goto out;
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}
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