Commit:     656dad312fb41ed95ef08325e9df9bece3aacbbb
Parent:     3e4fdaf8aebe489e8e59826fdf78cb64356d2ad0
Author:     Ingo Molnar <[EMAIL PROTECTED]>
AuthorDate: Sat Feb 10 01:46:36 2007 -0800
Committer:  Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Sun Feb 11 11:18:07 2007 -0800

    [PATCH] highmem: catch illegal nesting
    Catch illegally nested kmap_atomic()s even if the page that is mapped by
    the 'inner' instance is from lowmem.
    This avoids spuriously zapped kmap-atomic ptes and turns hard to find
    crashes into clear asserts at the bug site.
    Signed-off-by: Ingo Molnar <[EMAIL PROTECTED]>
    Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
    Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
 arch/i386/mm/highmem.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/i386/mm/highmem.c b/arch/i386/mm/highmem.c
index e0fa6cb..bb2de10 100644
--- a/arch/i386/mm/highmem.c
+++ b/arch/i386/mm/highmem.c
@@ -33,13 +33,14 @@ void *kmap_atomic(struct page *page, enum km_type type)
        /* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
+       idx = type + KM_TYPE_NR*smp_processor_id();
+       BUG_ON(!pte_none(*(kmap_pte-idx)));
        if (!PageHighMem(page))
                return page_address(page);
-       idx = type + KM_TYPE_NR*smp_processor_id();
        vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
-       if (!pte_none(*(kmap_pte-idx)))
-               BUG();
        set_pte(kmap_pte-idx, mk_pte(page, kmap_prot));
        return (void*) vaddr;
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