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revert "highmem: catch illegal nesting"

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	commit 656dad312f
	Author: Ingo Molnar <mingo@elte.hu>
	Date:   Sat Feb 10 01:46:36 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.

Problem is, a get_zeroed_page(GFP_KERNEL) from interrupt context will trigger
this check if non-irq code on this CPU holds a KM_USER0 mapping.  But that
get_zeroed_page() will never be altering the kmap slot anyway due to the
GFP_KERNEL.

Cc: Christoph Lameter <clameter@sgi.com>
Cc: 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:
Andrew Morton 2007-09-11 15:24:10 -07:00 committed by Linus Torvalds
parent 298a5df45d
commit 4150d3f549
1 changed files with 3 additions and 4 deletions
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7
arch/i386/mm/highmem.c
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@ -34,17 +34,16 @@ void *kmap_atomic_prot(struct page *page, enum km_type type, pgprot_t prot)
/* 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);
BUG_ON(!pte_none(*(kmap_pte-idx)));
set_pte(kmap_pte-idx, mk_pte(page, prot));
arch_flush_lazy_mmu_mode();
return (void*) vaddr;
return (void *)vaddr;
}
void *kmap_atomic(struct page *page, enum km_type type)