[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 <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -33,13 +33,14 @@ void *kmap_atomic(struct page *page, enum km_type type)
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/* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
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pagefault_disable();
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idx = type + KM_TYPE_NR*smp_processor_id();
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BUG_ON(!pte_none(*(kmap_pte-idx)));
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if (!PageHighMem(page))
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return page_address(page);
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idx = type + KM_TYPE_NR*smp_processor_id();
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vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
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if (!pte_none(*(kmap_pte-idx)))
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BUG();
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set_pte(kmap_pte-idx, mk_pte(page, kmap_prot));
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return (void*) vaddr;
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