On 19.07.19 15:52, David Hildenbrand wrote:
> We don't allow to offline memory block devices that belong to multiple
> numa nodes. Therefore, such devices can never get removed. It is
> sufficient to process a single node when removing the memory block. No
> need to iterate over each and every PFN.
>
> We already have the nid stored for each memory block. Make sure that
> the nid always has a sane value.
>
> Please note that checking for node_online(nid) is not required. If we
> would have a memory block belonging to a node that is no longer offline,
> then we would have a BUG in the node offlining code.
>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Cc: "Rafael J. Wysocki" <rafael@xxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: David Hildenbrand <david@xxxxxxxxxx>
> Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
> Cc: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxx>
> Cc: Oscar Salvador <osalvador@xxxxxxx>
> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
> ---
>
> v1 -> v2:
> - Remove the "mixed nid" part, add a comment instead. Drop the warning.
>
> ---
> drivers/base/memory.c | 1 +
> drivers/base/node.c | 39 +++++++++++++++------------------------
> 2 files changed, 16 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/base/memory.c b/drivers/base/memory.c
> index 20c39d1bcef8..154d5d4a0779 100644
> --- a/drivers/base/memory.c
> +++ b/drivers/base/memory.c
> @@ -674,6 +674,7 @@ static int init_memory_block(struct memory_block **memory,
> mem->state = state;
> start_pfn = section_nr_to_pfn(mem->start_section_nr);
> mem->phys_device = arch_get_memory_phys_device(start_pfn);
> + mem->nid = NUMA_NO_NODE;
>
> ret = register_memory(mem);
>
> diff --git a/drivers/base/node.c b/drivers/base/node.c
> index 75b7e6f6535b..840c95baa1d8 100644
> --- a/drivers/base/node.c
> +++ b/drivers/base/node.c
> @@ -759,8 +759,6 @@ static int register_mem_sect_under_node(struct memory_block *mem_blk,
> int ret, nid = *(int *)arg;
> unsigned long pfn, sect_start_pfn, sect_end_pfn;
>
> - mem_blk->nid = nid;
> -
> sect_start_pfn = section_nr_to_pfn(mem_blk->start_section_nr);
> sect_end_pfn = section_nr_to_pfn(mem_blk->end_section_nr);
> sect_end_pfn += PAGES_PER_SECTION - 1;
> @@ -789,6 +787,13 @@ static int register_mem_sect_under_node(struct memory_block *mem_blk,
> if (page_nid != nid)
> continue;
> }
> +
> + /*
> + * If this memory block spans multiple nodes, we only indicate
> + * the last processed node.
> + */
> + mem_blk->nid = nid;
> +
> ret = sysfs_create_link_nowarn(&node_devices[nid]->dev.kobj,
> &mem_blk->dev.kobj,
> kobject_name(&mem_blk->dev.kobj));
> @@ -804,32 +809,18 @@ static int register_mem_sect_under_node(struct memory_block *mem_blk,
> }
>
> /*
> - * Unregister memory block device under all nodes that it spans.
> - * Has to be called with mem_sysfs_mutex held (due to unlinked_nodes).
> + * Unregister a memory block device under the node it spans. Memory blocks
> + * with multiple nodes cannot be offlined and therefore also never be removed.
> */
> void unregister_memory_block_under_nodes(struct memory_block *mem_blk)
> {
> - unsigned long pfn, sect_start_pfn, sect_end_pfn;
> - static nodemask_t unlinked_nodes;
> -
> - nodes_clear(unlinked_nodes);
> - sect_start_pfn = section_nr_to_pfn(mem_blk->start_section_nr);
> - sect_end_pfn = section_nr_to_pfn(mem_blk->end_section_nr);
> - for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
> - int nid;
> + if (mem_blk->nid == NUMA_NO_NODE)
> + return;
>
> - nid = get_nid_for_pfn(pfn);
> - if (nid < 0)
> - continue;
> - if (!node_online(nid))
> - continue;
> - if (node_test_and_set(nid, unlinked_nodes))
> - continue;
> - sysfs_remove_link(&node_devices[nid]->dev.kobj,
> - kobject_name(&mem_blk->dev.kobj));
> - sysfs_remove_link(&mem_blk->dev.kobj,
> - kobject_name(&node_devices[nid]->dev.kobj));
> - }
> + sysfs_remove_link(&node_devices[mem_blk->nid]->dev.kobj,
> + kobject_name(&mem_blk->dev.kobj));
> + sysfs_remove_link(&mem_blk->dev.kobj,
> + kobject_name(&node_devices[mem_blk->nid]->dev.kobj));
> }
>
> int link_mem_sections(int nid, unsigned long start_pfn, unsigned long end_pfn)
>
Just a note that this was actually also a bugfix as noted by Chris.
If the memory we are removing was never onlined,
get_nid_for_pfn()->pfn_to_nid() will return garbage. Removing will
succeed but links will remain in place.
Can be triggered by
1. hotplugging a DIMM to node 1
2. not onlining the memory blocks
3. unplugging it
4. re-plugging it to node 1
We will trigger the BUG_ON(ret) in add_memory_resource(), because
link_mem_sections() will return with -EEXIST.
--
Thanks,
David / dhildenb
