[PATCH v4] mm, page_alloc: find movable zone after kernel text

[Baoquan He]

In find_zone_movable_pfns_for_nodes(), when try to find the starting
PFN movable zone begins at in each node, kernel text position is not
considered. KASLR may put kernel after which movable zone begins.

Fix it by finding movable zone after kernel text on that node.

Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>
---
 mm/page_alloc.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 1521100f1e63..5bc1a47dafda 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6547,7 +6547,7 @@ static unsigned long __init early_calculate_totalpages(void)
 static void __init find_zone_movable_pfns_for_nodes(void)
 {
 	int i, nid;
-	unsigned long usable_startpfn;
+	unsigned long usable_startpfn, kernel_endpfn, arch_startpfn;
 	unsigned long kernelcore_node, kernelcore_remaining;
 	/* save the state before borrow the nodemask */
 	nodemask_t saved_node_state = node_states[N_MEMORY];
@@ -6649,8 +6649,9 @@ static void __init find_zone_movable_pfns_for_nodes(void)
 	if (!required_kernelcore || required_kernelcore >= totalpages)
 		goto out;
 
+	kernel_endpfn = PFN_UP(__pa_symbol(_end));
 	/* usable_startpfn is the lowest possible pfn ZONE_MOVABLE can be at */
-	usable_startpfn = arch_zone_lowest_possible_pfn[movable_zone];
+	arch_startpfn = arch_zone_lowest_possible_pfn[movable_zone];
 
 restart:
 	/* Spread kernelcore memory as evenly as possible throughout nodes */
@@ -6659,6 +6660,16 @@ static void __init find_zone_movable_pfns_for_nodes(void)
 		unsigned long start_pfn, end_pfn;
 
 		/*
+		 * KASLR may put kernel near tail of node memory,
+		 * start after kernel on that node to find PFN
+		 * at which zone begins.
+		 */
+		if (pfn_to_nid(kernel_endpfn) == nid)
+		        usable_startpfn = max(arch_startpfn, kernel_endpfn);
+		else
+		        usable_startpfn = arch_startpfn;
+
+		/*
 		 * Recalculate kernelcore_node if the division per node
 		 * now exceeds what is necessary to satisfy the requested
 		 * amount of memory for the kernel
-- 
2.13.6