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authorDave Hansen <dave@linux.vnet.ibm.com>2009-02-12 12:36:04 +0000
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2009-02-13 16:37:45 +1100
commit06eccea6c34e00c8fedce49229ed35fa84619fb7 (patch)
tree3f548f91cec3e10dc28a7ab36728e266cb41fb44 /arch/powerpc/mm
parentfbc78b07ba53ace155f27491c81a009e541a93ad (diff)
powerpc/mm: Fix numa reserve bootmem page selection
Fix the powerpc NUMA reserve bootmem page selection logic. commit 8f64e1f2d1e09267ac926e15090fd505c1c0cbcb (powerpc: Reserve in bootmem lmb reserved regions that cross NUMA nodes) changed the logic for how the powerpc LMB reserved regions were converted to bootmen reserved regions. As the folowing discussion reports, the new logic was not correct. mark_reserved_regions_for_nid() goes through each LMB on the system that specifies a reserved area. It searches for active regions that intersect with that LMB and are on the specified node. It attempts to bootmem-reserve only the area where the active region and the reserved LMB intersect. We can not reserve things on other nodes as they may not have bootmem structures allocated, yet. We base the size of the bootmem reservation on two possible things. Normally, we just make the reservation start and stop exactly at the start and end of the LMB. However, the LMB reservations are not aware of NUMA nodes and on occasion a single LMB may cross into several adjacent active regions. Those may even be on different NUMA nodes and will require separate calls to the bootmem reserve functions. So, the bootmem reservation must be trimmed to fit inside the current active region. That's all fine and dandy, but we trim the reservation in a page-aligned fashion. That's bad because we start the reservation at a non-page-aligned address: physbase. The reservation may only span 2 bytes, but that those bytes may span two pfns and cause a reserve_size of 2*PAGE_SIZE. Take the case where you reserve 0x2 bytes at 0x0fff and where the active region ends at 0x1000. You'll jump into that if() statment, but node_ar.end_pfn=0x1 and start_pfn=0x0. You'll end up with a reserve_size=0x1000, and then call reserve_bootmem_node(node, physbase=0xfff, size=0x1000); 0x1000 may not be on the same node as 0xfff. Oops. In almost all the vm code, end_<anything> is not inclusive. If you have an end_pfn of 0x1234, page 0x1234 is not included in the range. Using PFN_UP instead of the (>> >> PAGE_SHIFT) will make this consistent with the other VM code. We also need to do math for the reserved size with physbase instead of start_pfn. node_ar.end_pfn << PAGE_SHIFT is *precisely* the end of the node. However, (start_pfn << PAGE_SHIFT) is *NOT* precisely the beginning of the reserved area. That is, of course, physbase. If we don't use physbase here, the reserve_size can be made too large. From: Dave Hansen <dave@linux.vnet.ibm.com> Tested-by: Geoff Levand <geoffrey.levand@am.sony.com> Tested on PS3. Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc/mm')
-rw-r--r--arch/powerpc/mm/numa.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index 7393bd76d69..5ac08b8ab65 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -19,6 +19,7 @@
#include <linux/notifier.h>
#include <linux/lmb.h>
#include <linux/of.h>
+#include <linux/pfn.h>
#include <asm/sparsemem.h>
#include <asm/prom.h>
#include <asm/system.h>
@@ -882,7 +883,7 @@ static void mark_reserved_regions_for_nid(int nid)
unsigned long physbase = lmb.reserved.region[i].base;
unsigned long size = lmb.reserved.region[i].size;
unsigned long start_pfn = physbase >> PAGE_SHIFT;
- unsigned long end_pfn = ((physbase + size) >> PAGE_SHIFT);
+ unsigned long end_pfn = PFN_UP(physbase + size);
struct node_active_region node_ar;
unsigned long node_end_pfn = node->node_start_pfn +
node->node_spanned_pages;
@@ -908,7 +909,7 @@ static void mark_reserved_regions_for_nid(int nid)
*/
if (end_pfn > node_ar.end_pfn)
reserve_size = (node_ar.end_pfn << PAGE_SHIFT)
- - (start_pfn << PAGE_SHIFT);
+ - physbase;
/*
* Only worry about *this* node, others may not
* yet have valid NODE_DATA().