This patch is for implementing optimized pfn_valid() for sparsemem_vmemmap.
By this, we can avoid accessing mem_section[] in usual codes.
(memory hotplug will access it.)
This patch checks vmem_map is mapped or not by get_user().
If fault, pfn is not valid.
Because sparsemem_vmemmap's virtual mem_map per section is always aligned to
PAGE_SIZE, pfn_valid(pfn) can assume a whole struct page is fully mapped.
So it only access the first byte.
How to use:
1. set ARCH_SPARSEMEM_VMEMMAP_OPT_PFNVALID config in arch/Kconfig
2. modify page fault handler in each arch to handle fault in mem_map range.
Signed-Off-By: KAMEZAWA Hiroyuki <[email protected]>
include/linux/mmzone.h | 10 ++++++++++
mm/Kconfig | 4 ++++
mm/sparse.c | 7 +++++++
3 files changed, 21 insertions(+)
Index: devel-2.6.20-rc1-mm1/include/linux/mmzone.h
===================================================================
--- devel-2.6.20-rc1-mm1.orig/include/linux/mmzone.h 2006-12-16 13:48:52.000000000 +0900
+++ devel-2.6.20-rc1-mm1/include/linux/mmzone.h 2006-12-16 14:43:08.000000000 +0900
@@ -752,12 +752,22 @@
return __nr_to_section(pfn_to_section_nr(pfn));
}
+#ifdef CONFIG_SPARSEMEM_VMEMMAP_OPT_PFNVALID
+extern int vmemmap_test_valid(struct page *pg);
+static inline int pfn_valid(unsigned long pfn)
+{
+ if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
+ return 0;
+ return vmemmap_test_valid(pfn_to_page(pfn));
+}
+#else
static inline int pfn_valid(unsigned long pfn)
{
if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
return 0;
return valid_section(__nr_to_section(pfn_to_section_nr(pfn)));
}
+#endif
/*
* These are _only_ used during initialisation, therefore they
Index: devel-2.6.20-rc1-mm1/mm/Kconfig
===================================================================
--- devel-2.6.20-rc1-mm1.orig/mm/Kconfig 2006-12-16 13:48:53.000000000 +0900
+++ devel-2.6.20-rc1-mm1/mm/Kconfig 2006-12-16 13:52:06.000000000 +0900
@@ -125,6 +125,10 @@
def_bool y
depends on ARCH_SPARSEMEM_VMEMMAP_STATIC
+config SPARSEMEM_VMEMMAP_OPT_PFNVALID
+ def_bool y
+ depends on SPARSEMEM_VMEMMAP && ARCH_SPARSEMEM_VMEMMAP_OPT_PFN_VALID
+
# eventually, we can have this option just 'select SPARSEMEM'
config MEMORY_HOTPLUG
bool "Allow for memory hot-add"
Index: devel-2.6.20-rc1-mm1/mm/sparse.c
===================================================================
--- devel-2.6.20-rc1-mm1.orig/mm/sparse.c 2006-12-16 13:48:53.000000000 +0900
+++ devel-2.6.20-rc1-mm1/mm/sparse.c 2006-12-16 14:03:41.000000000 +0900
@@ -108,6 +108,13 @@
int nid;
};
+int vmemmap_test_valid(struct page *pg)
+{
+ char byte;
+ /* vmemmap per section is always aligned to PAGE_SIZE */
+ return (__get_user(byte, (char __user *)pg) == 0);
+}
+
/* call backs for memory map */
static int
__init pte_alloc_vmemmap_boot(pmd_t *pmd, unsigned long addr, void *data)
-
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