Add CAP_HOTUNPLUG, which allows memory_hotplug to migrate a private node's folios for the purpose of hotunplugging memory.
Without this, hotunplug fails if any folio on the node is allocated. Add node_allows_hotunplug() - which returns true for any normal node and private nodes with CAP_HOTUNPLUG. Signed-off-by: Gregory Price <[email protected]> --- include/linux/node_private.h | 26 ++++++++++++++++++++++++++ mm/memory_hotplug.c | 4 ++-- 2 files changed, 28 insertions(+), 2 deletions(-) diff --git a/include/linux/node_private.h b/include/linux/node_private.h index 655fe9ec5cb61..7b617b1fa9c28 100644 --- a/include/linux/node_private.h +++ b/include/linux/node_private.h @@ -14,6 +14,7 @@ struct page; */ #define NODE_PRIVATE_CAP_RECLAIM (1UL << 0) /* allow mm reclaim */ #define NODE_PRIVATE_CAP_USER_NUMA (1UL << 1) /* allow mempolicy */ +#define NODE_PRIVATE_CAP_HOTUNPLUG (1UL << 2) /* allow hot-unplug */ /** * struct node_private - Per-node container for N_MEMORY_PRIVATE nodes @@ -97,6 +98,26 @@ static inline bool node_allows_user_numa(int nid) return ret; } +/** + * node_allows_hotunplug - may hot-unplug migrate this node's folios? + * @nid: the node to test + * + * True for normal nodes and private nodes opted into CAP_HOTUNPLUG. + */ +static inline bool node_allows_hotunplug(int nid) +{ + struct node_private *np; + bool ret; + + if (!node_state(nid, N_MEMORY_PRIVATE)) + return true; + rcu_read_lock(); + np = rcu_dereference(NODE_DATA(nid)->node_private); + ret = np && (np->caps & NODE_PRIVATE_CAP_HOTUNPLUG); + rcu_read_unlock(); + return ret; +} + #else /* !CONFIG_NUMA */ static inline bool folio_is_private_node(struct folio *folio) @@ -124,6 +145,11 @@ static inline bool node_allows_user_numa(int nid) return true; } +static inline bool node_allows_hotunplug(int nid) +{ + return true; +} + #endif /* CONFIG_NUMA */ #if defined(CONFIG_NUMA) && defined(CONFIG_MEMORY_HOTPLUG) diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 1f42ed303366c..e9573f90e0dcd 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1943,8 +1943,8 @@ static int do_migrate_range(unsigned long start_pfn, unsigned long end_pfn) goto put_folio; } - /* Private node folios cannot migrate, fail outright */ - if (folio_is_private_node(folio)) { + /* Fail outright on private nodes w/o hotunplug support */ + if (!node_allows_hotunplug(folio_nid(folio))) { pr_info_ratelimited("memory offline refused: node %d pfn %lx\n", folio_nid(folio), pfn); folio_put(folio); -- 2.53.0-Meta
