[PATCH 0/2] Fix a bug and cleanup NUMA boot-time code

[PATCH 0/2] Fix a bug and cleanup NUMA boot-time code

[Dave Hansen]

The first patch in this series is a genuine bug fix.  The rest
are really just an RFC.

Jon introduced a bug a while ago.  I introduced another when
trying to fix Jon's bug.  I refuse to accept personal blame for
this and, instead, blame the code. :)

The reset of the series are "cleanups" that I think will help
clarify the code in numa.c and work to ensure that the next
bonehead like me is not as able to easily muck up the code. :)

The cleanups increase in impact and intrusiveness as the series
goes along, so please consider them an RFC.  But, what I really
want to figure out is a safer way to initialize NODE_DATA() and
start using it as we bring up bootmem on all the nodes.

[PATCH 1/2] remove unused i var

[Dave Hansen]

---

 linux-2.6.git-dave/arch/powerpc/mm/numa.c |    1 -
 1 file changed, 1 deletion(-)

diff -puN arch/powerpc/mm/numa.c~remove-unused-i-var arch/powerpc/mm/numa.c
--- linux-2.6.git/arch/powerpc/mm/numa.c~remove-unused-i-var	2008-12-11 09:12:57.000000000 -0800
+++ linux-2.6.git-dave/arch/powerpc/mm/numa.c	2008-12-11 09:12:57.000000000 -0800
@@ -929,7 +929,6 @@ static void mark_reserved_regions_for_ni
 void __init do_init_bootmem(void)
 {
 	int nid;
-	unsigned int i;
 
 	min_low_pfn = 0;
 	max_low_pfn = lmb_end_of_DRAM() >> PAGE_SHIFT;
_

[PATCH 2/2] fix bootmem reservation on uninitialized node

[Dave Hansen]

careful_allocation() was calling into the bootemem allocator for
nodes which had not been fully initialized and caused a previous
bug.  http://patchwork.ozlabs.org/patch/10528/  So, I merged a
few broken out loops in do_init_bootmem() to fix it.  That changed
the code ordering.

I think this bug is triggered by having reserved areas for a node
which are spanned by another node's contents.  In the
mark_reserved_regions_for_nid() code, we attempt to reserve the
area for a node before we have allocated the NODE_DATA() for that
nid.  We do this since I reordered that loop.  I suck.

This may only present on some systems that have 16GB pages
reserved.  But, it can probably happen on any system that is
trying to reserve large swaths of memory that happen to span other
nodes' contents.

This patch ensures that we do not touch bootmem for any node which
has not been initialized.

Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
---

 linux-2.6.git-dave/arch/powerpc/mm/numa.c |   15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff -puN arch/powerpc/mm/numa.c~fix-bad-node-reserve arch/powerpc/mm/numa.c
--- linux-2.6.git/arch/powerpc/mm/numa.c~fix-bad-node-reserve	2008-12-10 14:54:18.000000000 -0800
+++ linux-2.6.git-dave/arch/powerpc/mm/numa.c	2008-12-10 14:55:33.000000000 -0800
@@ -901,10 +901,17 @@ static void mark_reserved_regions_for_ni
 			if (end_pfn > node_ar.end_pfn)
 				reserve_size = (node_ar.end_pfn << PAGE_SHIFT)
 					- (start_pfn << PAGE_SHIFT);
-			dbg("reserve_bootmem %lx %lx nid=%d\n", physbase,
-				reserve_size, node_ar.nid);
-			reserve_bootmem_node(NODE_DATA(node_ar.nid), physbase,
-						reserve_size, BOOTMEM_DEFAULT);
+			/*
+			 * Only worry about *this* node, others may not
+			 * yet have valid NODE_DATA().
+			 */
+			if (node_ar.nid == nid) {
+				dbg("reserve_bootmem %lx %lx nid=%d\n",
+					physbase, reserve_size, node_ar.nid);
+				reserve_bootmem_node(NODE_DATA(node_ar.nid),
+						physbase, reserve_size,
+						BOOTMEM_DEFAULT);
+			}
 			/*
 			 * if reserved region is contained in the active region
 			 * then done.
_

Re: [PATCH 0/2] Fix a bug and cleanup NUMA boot-time code

[Dave Hansen]

Gah, sorry.  I resent my description for the whole series from yesterday
instead of one just for these bug fixes.

The first patch removes a warning in numa.c that I just caused.

The second one is a rework of the bug fix that was at the head of the
series yesterday, addressing some comments that Paul made.

-- Dave