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[PATCH] highmem: catch illegal nesting

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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 <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Ingo Molnar 2007-02-10 01:46:36 -08:00 committed by Linus Torvalds
parent 3e4fdaf8ae
commit 656dad312f
1 changed files with 4 additions and 3 deletions
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7
arch/i386/mm/highmem.c
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@ -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 */
pagefault_disable();
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;