linux-kernel - Re: [PATCH] mm: clear N_HIGH_MEMORY map before se set it again -v4

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Message-ID: <4A3D7419.8040305@kernel.org>
Date:	Sat, 20 Jun 2009 16:43:21 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Nathan Lynch <ntl@...ox.com>
CC:	Christoph Lameter <cl@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>, mingo@...e.hu,
	mel@....ul.ie, tglx@...utronix.de, hpa@...or.com,
	suresh.b.siddha@...el.com, linux-kernel@...r.kernel.org,
	viro@...iv.linux.org.uk, rusty@...tcorp.com.au, steiner@....com,
	rientjes@...gle.com, containers@...ts.linux-foundation.org
Subject: Re: [PATCH] mm: clear N_HIGH_MEMORY map before se set it again -v4

please check

[PATCH] x86: only clear node_states for 64bit

Nathan reported that
| commit 73d60b7f747176dbdff826c4127d22e1fd3f9f74
| Author: Yinghai Lu <yinghai@...nel.org>
| Date:   Tue Jun 16 15:33:00 2009 -0700
|
|    page-allocator: clear N_HIGH_MEMORY map before we set it again
|    
|    SRAT tables may contains nodes of very small size.  The arch code may
|    decide to not activate such a node.  However, currently the early boot
|    code sets N_HIGH_MEMORY for such nodes.  These nodes therefore seem to be
|    active although these nodes have no present pages.
|    
|    For 64bit N_HIGH_MEMORY == N_NORMAL_MEMORY, so that works for 64 bit too

the cpuset.mems cgroup attribute on an i386 kvm guest

try to fix it by only clear node_states[N_NORMAL_MEMORY] for 64bit only.
and need to do save/restore for that in find_zone_movable_pfn

Reported-by: Nathan Lynch <ntl@...ox.com>
Signed-off-by: Yinghai Lu <yinghai@...nel.org>

---
 arch/x86/mm/init_64.c |    2 ++
 mm/page_alloc.c       |   13 +++++++------
 2 files changed, 9 insertions(+), 6 deletions(-)

Index: linux-2.6/arch/x86/mm/init_64.c
===================================================================
--- linux-2.6.orig/arch/x86/mm/init_64.c
+++ linux-2.6/arch/x86/mm/init_64.c
@@ -598,6 +598,8 @@ void __init paging_init(void)
 
 	sparse_memory_present_with_active_regions(MAX_NUMNODES);
 	sparse_init();
+	/* clear the default setting with node 0 */
+	nodes_clear(node_states[N_NORMAL_MEMORY]);
 	free_area_init_nodes(max_zone_pfns);
 }
 
Index: linux-2.6/mm/page_alloc.c
===================================================================
--- linux-2.6.orig/mm/page_alloc.c
+++ linux-2.6/mm/page_alloc.c
@@ -4038,6 +4038,8 @@ static void __init find_zone_movable_pfn
 	int i, nid;
 	unsigned long usable_startpfn;
 	unsigned long kernelcore_node, kernelcore_remaining;
+	/* save the state before borrow the nodemask */
+	nodemask_t saved_node_state = node_states[N_HIGH_MEMORY];
 	unsigned long totalpages = early_calculate_totalpages();
 	int usable_nodes = nodes_weight(node_states[N_HIGH_MEMORY]);
 
@@ -4065,7 +4067,7 @@ static void __init find_zone_movable_pfn
 
 	/* If kernelcore was not specified, there is no ZONE_MOVABLE */
 	if (!required_kernelcore)
-		return;
+		goto out;
 
 	/* usable_startpfn is the lowest possible pfn ZONE_MOVABLE can be at */
 	find_usable_zone_for_movable();
@@ -4164,6 +4166,10 @@ restart:
 	for (nid = 0; nid < MAX_NUMNODES; nid++)
 		zone_movable_pfn[nid] =
 			roundup(zone_movable_pfn[nid], MAX_ORDER_NR_PAGES);
+
+out:
+	/* restore the node_state */
+	node_states[N_HIGH_MEMORY] = saved_node_state;
 }
 
 /* Any regular memory on that node ? */
@@ -4248,11 +4254,6 @@ void __init free_area_init_nodes(unsigne
 						early_node_map[i].start_pfn,
 						early_node_map[i].end_pfn);
 
-	/*
-	 * find_zone_movable_pfns_for_nodes/early_calculate_totalpages init
-	 * that node_mask, clear it at first
-	 */
-	nodes_clear(node_states[N_HIGH_MEMORY]);
 	/* Initialise every node */
 	mminit_verify_pageflags_layout();
 	setup_nr_node_ids();
--
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