On 2015/8/24 1:06, Tang Chen wrote:
> The commit below adds hot-added memory range to memblock, after
> creating pgdat for new node.
>
> commit f9126ab9241f66562debf69c2c9d8fee32ddcc53
> Author: Xishi Qiu <qiuxishi@xxxxxxxxxx>
> Date: Fri Aug 14 15:35:16 2015 -0700
>
> memory-hotplug: fix wrong edge when hot add a new node
>
> But there is a problem:
>
> add_memory()
> |--> hotadd_new_pgdat()
> |--> free_area_init_node()
> |--> get_pfn_range_for_nid()
> |--> find start_pfn and end_pfn in memblock
> |--> ......
> |--> memblock_add_node(start, size, nid) -------- Here, just too late.
>
> get_pfn_range_for_nid() will find that start_pfn and end_pfn are both 0.
> As a result, when adding memory, dmesg will give the following wrong message.
>
> [ 2007.577000] Initmem setup node 5 [mem 0x0000000000000000-0xffffffffffffffff]
> [ 2007.584000] On node 5 totalpages: 0
> [ 2007.585000] Built 5 zonelists in Node order, mobility grouping on. Total pages: 32588823
> [ 2007.594000] Policy zone: Normal
> [ 2007.598000] init_memory_mapping: [mem 0x60000000000-0x607ffffffff]
>
> The solution is simple, just add the memory range to memblock a little earlier,
> before hotadd_new_pgdat().
>
> Signed-off-by: Tang Chen <tangchen@xxxxxxxxxxxxxx>
> ---
> mm/memory_hotplug.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 6da82bc..9b78aff 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1248,6 +1248,14 @@ int __ref add_memory(int nid, u64 start, u64 size)
>
> mem_hotplug_begin();
>
> + /*
> + * Add new range to memblock so that when hotadd_new_pgdat() is called to
> + * allocate new pgdat, get_pfn_range_for_nid() will be able to find this
> + * new range and calculate total pages correctly. The range will be remove
> + * at hot-remove time.
> + */
> + memblock_add_node(start, size, nid);
> +
Hi Tang,
Looks fine to me.
If we add memblock_add_node() here, we should reset the managed pages and present pages,
so please revert my patch which Andrew has already merged into mm-tree.
"[PATCH 2/2] memory-hotplug: remove reset_node_managed_pages() and reset_node_managed_pages() in hotadd_new_pgdat()"
Thanks,
Xishi Qiu
> new_node = !node_online(nid);
> if (new_node) {
> pgdat = hotadd_new_pgdat(nid, start);
> @@ -1277,7 +1285,6 @@ int __ref add_memory(int nid, u64 start, u64 size)
>
> /* create new memmap entry */
> firmware_map_add_hotplug(start, start + size, "System RAM");
> - memblock_add_node(start, size, nid);
>
> goto out;
>
> @@ -1286,6 +1293,7 @@ error:
> if (new_pgdat)
> rollback_node_hotadd(nid, pgdat);
> release_memory_resource(res);
> + memblock_remove(start, size);
>
> out:
> mem_hotplug_done();
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