revert "highmem: catch illegal nesting"
Revert
commit 656dad312fb41ed95ef08325e9df9bece3aacbbb
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>
diff --git a/arch/i386/mm/highmem.c b/arch/i386/mm/highmem.c
index ad8d86c..1c3bf95 100644
--- a/arch/i386/mm/highmem.c
+++ b/arch/i386/mm/highmem.c
@@ -34,17 +34,16 @@
/* 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)