@@ -738,17 +738,6 @@ void __init x86_numa_init(void)
numa_init(dummy_numa_init);
}
-static void __init init_memory_less_node(int nid)
-{
- /* Allocate and initialize node data. Memory-less node is now online.*/
- alloc_node_data(nid);
- free_area_init_memoryless_node(nid);
-
- /*
- * All zonelists will be built later in start_kernel() after per cpu
- * areas are initialized.
- */
-}
/*
* A node may exist which has one or more Generic Initiators but no CPUs and no
@@ -766,9 +755,18 @@ void __init init_gi_nodes(void)
{
int nid;
+ /*
+ * Exclude this node from
+ * bringup_nonboot_cpus
+ * cpu_up
+ * __try_online_node
+ * register_one_node
+ * because node_subsys is not initialized yet.
+ * TODO remove dependency on node_online
+ */
for_each_node_state(nid, N_GENERIC_INITIATOR)
if (!node_online(nid))
- init_memory_less_node(nid);
+ node_set_online(nid);
}
/*
@@ -798,8 +796,17 @@ void __init init_cpu_to_node(void)
if (node == NUMA_NO_NODE)
continue;
+ /*
+ * Exclude this node from
+ * bringup_nonboot_cpus
+ * cpu_up
+ * __try_online_node
+ * register_one_node
+ * because node_subsys is not initialized yet.
+ * TODO remove dependency on node_online
+ */
if (!node_online(node))
- init_memory_less_node(node);
+ node_set_online(node);
numa_set_node(cpu, node);
}
@@ -2453,7 +2453,6 @@ static inline spinlock_t *pud_lock(struct mm_struct *mm, pud_t *pud)
}
extern void __init pagecache_init(void);
-extern void __init free_area_init_memoryless_node(int nid);
extern void free_initmem(void);
/*
@@ -7698,7 +7698,7 @@ static void __init free_area_init_node(int nid)
free_area_init_core(pgdat);
}
-void __init free_area_init_memoryless_node(int nid)
+static void __init free_area_init_memoryless_node(int nid)
{
free_area_init_node(nid);
}
On x86, prior to ("mm: handle uninitialized numa nodes gracecully"), NUMA nodes could be allocated at three different places. - numa_register_memblks - init_cpu_to_node - init_gi_nodes All these calls happen at setup_arch, and have the following order: setup_arch ... x86_numa_init numa_init numa_register_memblks ... init_cpu_to_node init_memory_less_node alloc_node_data free_area_init_memoryless_node init_gi_nodes init_memory_less_node alloc_node_data free_area_init_memoryless_node numa_register_memblks() is only interested in those nodes which have memory, so it skips over any memoryless node it founds. Later on, when we have read ACPI's SRAT table, we call init_cpu_to_node() and init_gi_nodes(), which initialize any memoryless node we might have that have either CPU or Initiator affinity, meaning we allocate pg_data_t struct for them and we mark them as ONLINE. So far so good, but the thing is that after ("mm: handle uninitialized numa nodes gracefully"), we allocate all possible NUMA nodes in free_area_init(), meaning we have a picture like the following: setup_arch x86_numa_init numa_init numa_register_memblks <-- allocate non-memoryless node x86_init.paging.pagetable_init ... free_area_init free_area_init_memoryless <-- allocate memoryless node init_cpu_to_node alloc_node_data <-- allocate memoryless node with CPU free_area_init_memoryless_node init_gi_nodes alloc_node_data <-- allocate memoryless node with Initiator free_area_init_memoryless_node free_area_init() already allocates all possible NUMA nodes, but init_cpu_to_node() and init_gi_nodes() are clueless about that, so they go ahead and allocate a new pg_data_t struct without checking anything, meaning we end up allocating twice. It should be mad clear that this only happens in the case where memoryless NUMA node happens to have a CPU/Initiator affinity. So get rid of init_memory_less_node() and just set the node online. Note that setting the node online is needed, otherwise we choke down the chain when bringup_nonboot_cpus() ends up calling __try_online_node()->register_one_node()->... and we blow up in bus_add_device(). Like can be seen here: ========= [ 0.585060] BUG: kernel NULL pointer dereference, address: 0000000000000060 [ 0.586091] #PF: supervisor read access in kernel mode [ 0.586831] #PF: error_code(0x0000) - not-present page [ 0.586930] PGD 0 P4D 0 [ 0.586930] Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC PTI [ 0.586930] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.17.0-rc4-1-default+ #45 [ 0.586930] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.0.0-prebuilt.qemu-project.org 04/4 [ 0.586930] RIP: 0010:bus_add_device+0x5a/0x140 [ 0.586930] Code: 8b 74 24 20 48 89 df e8 84 96 ff ff 85 c0 89 c5 75 38 48 8b 53 50 48 85 d2 0f 84 bb 00 004 [ 0.586930] RSP: 0000:ffffc9000022bd10 EFLAGS: 00010246 [ 0.586930] RAX: 0000000000000000 RBX: ffff888100987400 RCX: ffff8881003e4e19 [ 0.586930] RDX: ffff8881009a5e00 RSI: ffff888100987400 RDI: ffff888100987400 [ 0.586930] RBP: 0000000000000000 R08: ffff8881003e4e18 R09: ffff8881003e4c98 [ 0.586930] R10: 0000000000000000 R11: ffff888100402bc0 R12: ffffffff822ceba0 [ 0.586930] R13: 0000000000000000 R14: ffff888100987400 R15: 0000000000000000 [ 0.586930] FS: 0000000000000000(0000) GS:ffff88853fc00000(0000) knlGS:0000000000000000 [ 0.586930] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 0.586930] CR2: 0000000000000060 CR3: 000000000200a001 CR4: 00000000001706b0 [ 0.586930] Call Trace: [ 0.586930] <TASK> [ 0.586930] device_add+0x4c0/0x910 [ 0.586930] __register_one_node+0x97/0x2d0 [ 0.586930] __try_online_node+0x85/0xc0 [ 0.586930] try_online_node+0x25/0x40 [ 0.586930] cpu_up+0x4f/0x100 [ 0.586930] bringup_nonboot_cpus+0x4f/0x60 [ 0.586930] smp_init+0x26/0x79 [ 0.586930] kernel_init_freeable+0x130/0x2f1 [ 0.586930] ? rest_init+0x100/0x100 [ 0.586930] kernel_init+0x17/0x150 [ 0.586930] ? rest_init+0x100/0x100 [ 0.586930] ret_from_fork+0x22/0x30 [ 0.586930] </TASK> [ 0.586930] Modules linked in: [ 0.586930] CR2: 0000000000000060 [ 0.586930] ---[ end trace 0000000000000000 ]--- ========= The reason is simple, by the time bringup_nonboot_cpus() gets called, we did not register the node_subsys bus yet, so we crash when bus_add_device() tries to dereference bus()->p. The following shows the order of the calls: kernel_init_freeable smp_init bringup_nonboot_cpus ... bus_add_device() <- we did not register node_subsys yet do_basic_setup do_initcalls postcore_initcall(register_node_type); register_node_type subsys_system_register subsys_register bus_register <- register node_subsys bus Why setting the node online saves us then? Well, simply because __try_online_node() backs off when the node is online, meaning we do not end up calling register_one_node() in the first place. This is subtle, broken and deserves a deep analysis and thought about how to put this into shape, but for now let us have this easy fix for the leaking memory issue. Signed-off-by: Oscar Salvador <osalvador@suse.de> Acked-by: Michal Hocko <mhocko@suse.com> --- arch/x86/mm/numa.c | 33 ++++++++++++++++++++------------- include/linux/mm.h | 1 - mm/page_alloc.c | 2 +- 3 files changed, 21 insertions(+), 15 deletions(-)