On Thu 18-07-19 16:22:39, 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.
>
> Remember for each memory block if it belongs to no, a single, or mixed
> nodes, so we can use that information to skip unregistering or print a
> warning (essentially a safety net to catch BUGs).
I do not really like NUMA_NO_NODE - 1 thing. This is yet another invalid
node that is magic. Why should we even care? In other words why is this
patch an improvement?
> 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>
> ---
> drivers/base/memory.c | 1 +
> drivers/base/node.c | 40 ++++++++++++++++------------------------
> include/linux/memory.h | 4 +++-
> 3 files changed, 20 insertions(+), 25 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..29d27b8d5fda 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;
> }
> +
> + /* this memory block spans this node */
> + if (mem_blk->nid == NUMA_NO_NODE)
> + mem_blk->nid = nid;
> + else
> + mem_blk->nid = NUMA_NO_NODE - 1;
> +
> ret = sysfs_create_link_nowarn(&node_devices[nid]->dev.kobj,
> &mem_blk->dev.kobj,
> kobject_name(&mem_blk->dev.kobj));
> @@ -804,32 +809,19 @@ 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 ||
> + WARN_ON_ONCE(mem_blk->nid == NUMA_NO_NODE - 1))
> + 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)
> diff --git a/include/linux/memory.h b/include/linux/memory.h
> index 02e633f3ede0..c91af10d5fb4 100644
> --- a/include/linux/memory.h
> +++ b/include/linux/memory.h
> @@ -33,7 +33,9 @@ struct memory_block {
> void *hw; /* optional pointer to fw/hw data */
> int (*phys_callback)(struct memory_block *);
> struct device dev;
> - int nid; /* NID for this memory block */
> + int nid; /* NID for this memory block.
> + - NUMA_NO_NODE: uninitialized
> + - NUMA_NO_NODE - 1: mixed nodes */
> };
>
> int arch_get_memory_phys_device(unsigned long start_pfn);
> --
> 2.21.0
--
Michal Hocko
SUSE Labs
