[patch 38/47] vmemmap: allocate struct pages before 1:1 mapping

Martin Schwidefsky
2007-12-20T15:34:59Z

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From: Christian Borntraeger <borntraeger@de.ibm.com>

We have seen an oops in an OOM situation, where show_mem tried to
access the struct page of a dcss segment. The vmemmap code has
already created the 1:1 mapping but failed allocating the struct
pages. In the OOM case, show_mem now walks the memory. It uses
pfn_valid to detect if it may access the struct page. In the case
described above, the mapping was established and pfn_valid returned
true. As the struct pages were not allocated, the kernel oopsed.

We have to ensure that we have created the struct pages, before we
add a mapping pointing to the pages.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
---

arch/s390/mm/vmem.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

Index: quilt-2.6/arch/s390/mm/vmem.c
===================================================================
--- quilt-2.6.orig/arch/s390/mm/vmem.c
+++ quilt-2.6/arch/s390/mm/vmem.c
@@ -236,10 +236,10 @@ static int vmem_add_mem(unsigned long st
{
int ret;

- ret = vmem_add_range(start, size);
+ ret = vmem_add_mem_map(start, size);
if (ret)
return ret;
- return vmem_add_mem_map(start, size);
+ return vmem_add_range(start, size);
}

/*