[PATCH] mm/hugetlb: split hugetlb_cma in nodes with memory

[Barry Song]

Rather than splitting huge_cma in online nodes, it is better to do it in
nodes with memory.
For an ARM64 server with four numa nodes and only node0 has memory. If I
set hugetlb_cma=4G in bootargs,

without this patch, I got the below printk:
hugetlb_cma: reserve 4096 MiB, up to 1024 MiB per node
hugetlb_cma: reserved 1024 MiB on node 0
hugetlb_cma: reservation failed: err -12, node 1
hugetlb_cma: reservation failed: err -12, node 2
hugetlb_cma: reservation failed: err -12, node 3

hugetlb_cma size is broken once the system has nodes without memory.

With this patch, I got the below printk:
hugetlb_cma: reserve 4096 MiB, up to 4096 MiB per node
hugetlb_cma: reserved 4096 MiB on node 0

So this patch fixes the broken hugetlb_cma size on arm64.

Jonathan Cameron tested this patch on x86 platform. Jonathan figured out x86
is much different with arm64. hugetlb_cma size has never broken on x86.
On arm64 all nodes are marked online at the same time. On x86, only
nodes with memory are initially marked as online:
initmem_init()->x86_numa_init()->numa_init()->
numa_register_memblks()->alloc_node_data()->node_set_online()
So at time of the existing cma setup call only the memory containing nodes
are online. The other nodes are brought up much later.

Thus, the change is simply to fix ARM64.  A change is needed to x86 only
because the inherent assumptions in cma_hugetlb_reserve() have changed.

Fixes: cf11e85fc08c ("mm: hugetlb: optionally allocate gigantic hugepages using cma")
Cc: Roman Gushchin <guro at fb.com>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Will Deacon <will at kernel.org>
Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: Ingo Molnar <mingo at redhat.com>
Cc: Borislav Petkov <bp at alien8.de>
Cc: H. Peter Anvin <hpa at zytor.com>
Cc: Mike Kravetz <mike.kravetz at oracle.com>
Cc: Mike Rapoport <rppt at linux.ibm.com>
Cc: Andrew Morton <akpm at linux-foundation.org>
Cc: Anshuman Khandual <anshuman.khandual at arm.com>
Cc: Jonathan Cameron <jonathan.cameron at huawei.com>
Signed-off-by: Barry Song <song.bao.hua at hisilicon.com>
---
 arch/arm64/mm/init.c    | 18 +++++++++---------
 arch/x86/kernel/setup.c | 13 ++++++++++---
 mm/hugetlb.c            |  4 ++--
 3 files changed, 21 insertions(+), 14 deletions(-)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 1e93cfc7c47a..f6090ef6812b 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -420,15 +420,6 @@ void __init bootmem_init(void)
 
 	arm64_numa_init();
 
-	/*
-	 * must be done after arm64_numa_init() which calls numa_init() to
-	 * initialize node_online_map that gets used in hugetlb_cma_reserve()
-	 * while allocating required CMA size across online nodes.
-	 */
-#ifdef CONFIG_ARM64_4K_PAGES
-	hugetlb_cma_reserve(PUD_SHIFT - PAGE_SHIFT);
-#endif
-
 	/*
 	 * Sparsemem tries to allocate bootmem in memory_present(), so must be
 	 * done after the fixed reservations.
@@ -438,6 +429,15 @@ void __init bootmem_init(void)
 	sparse_init();
 	zone_sizes_init(min, max);
 
+	/*
+	 * must be done after zone_sizes_init() which calls node_set_state() to
+	 * setup node_states[N_MEMORY] that gets used in hugetlb_cma_reserve()
+	 * while allocating required CMA size across nodes with memory.
+	 */
+#ifdef CONFIG_ARM64_4K_PAGES
+	hugetlb_cma_reserve(PUD_SHIFT - PAGE_SHIFT);
+#endif
+
 	memblock_dump_all();
 }
 
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index a3767e74c758..fdb3a934b6c6 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1164,9 +1164,6 @@ void __init setup_arch(char **cmdline_p)
 	initmem_init();
 	dma_contiguous_reserve(max_pfn_mapped << PAGE_SHIFT);
 
-	if (boot_cpu_has(X86_FEATURE_GBPAGES))
-		hugetlb_cma_reserve(PUD_SHIFT - PAGE_SHIFT);
-
 	/*
 	 * Reserve memory for crash kernel after SRAT is parsed so that it
 	 * won't consume hotpluggable memory.
@@ -1180,6 +1177,16 @@ void __init setup_arch(char **cmdline_p)
 
 	x86_init.paging.pagetable_init();
 
+	/*
+	 * must be done after zone_sizes_init() which calls node_set_state() to
+	 * setup node_states[N_MEMORY] that gets used in hugetlb_cma_reserve()
+	 * while allocating required CMA size across nodes with memory.
+	 * And zone_sizes_init() is done in x86_init.paging.pagetable_init()
+	 * which is typically paging_init().
+	 */
+	if (boot_cpu_has(X86_FEATURE_GBPAGES))
+		hugetlb_cma_reserve(PUD_SHIFT - PAGE_SHIFT);
+
 	kasan_init();
 
 	/*
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index d293c823121e..3a0ad49187e4 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5699,12 +5699,12 @@ void __init hugetlb_cma_reserve(int order)
 	 * If 3 GB area is requested on a machine with 4 numa nodes,
 	 * let's allocate 1 GB on first three nodes and ignore the last one.
 	 */
-	per_node = DIV_ROUND_UP(hugetlb_cma_size, nr_online_nodes);
+	per_node = DIV_ROUND_UP(hugetlb_cma_size, num_node_state(N_MEMORY));
 	pr_info("hugetlb_cma: reserve %lu MiB, up to %lu MiB per node\n",
 		hugetlb_cma_size / SZ_1M, per_node / SZ_1M);
 
 	reserved = 0;
-	for_each_node_state(nid, N_ONLINE) {
+	for_each_node_state(nid, N_MEMORY) {
 		int res;
 
 		size = min(per_node, hugetlb_cma_size - reserved);
-- 
2.27.0