On 19.08.22 10:00, Muchun Song wrote: > The following commit offload per-node sysfs creation and removal to a kworker and > did not say why it is needed. And it also said "I don't know that this is > absolutely required". It seems like the author was not sure as well. Since it > only complicates the code, this patch will revert the changes to simplify the code. > > 39da08cb074c ("hugetlb: offload per node attribute registrations") > > We could use memory hotplug notifier to do per-node sysfs creation and removal > instead of inserting those operations to node registration and unregistration. > Then, it can reduce the code coupling between node.c and hugetlb.c. Also, it can > simplify the code. > > Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx> [...] > @@ -683,7 +626,6 @@ static int register_node(struct node *node, int num) > void unregister_node(struct node *node) > { > compaction_unregister_node(node); > - hugetlb_unregister_node(node); /* no-op, if memoryless node */ > node_remove_accesses(node); > node_remove_caches(node); > device_unregister(&node->dev); > @@ -905,74 +847,8 @@ void register_memory_blocks_under_node(int nid, unsigned long start_pfn, > (void *)&nid, func); > return; > } [...] > /* > * Create all node devices, which will properly link the node > * to applicable memory block devices and already created cpu devices. > diff --git a/include/linux/node.h b/include/linux/node.h > index 40d641a8bfb0..ea817b507f54 100644 > --- a/include/linux/node.h > +++ b/include/linux/node.h > @@ -2,15 +2,15 @@ > /* > * include/linux/node.h - generic node definition > * > - * This is mainly for topological representation. We define the > - * basic 'struct node' here, which can be embedded in per-arch > + * This is mainly for topological representation. We define the > + * basic 'struct node' here, which can be embedded in per-arch > * definitions of processors. > * > * Basic handling of the devices is done in drivers/base/node.c > - * and system devices are handled in drivers/base/sys.c. > + * and system devices are handled in drivers/base/sys.c. > * > * Nodes are exported via driverfs in the class/node/devices/ > - * directory. > + * directory. Unrelated changes. > */ > #ifndef _LINUX_NODE_H_ > #define _LINUX_NODE_H_ > @@ -18,7 +18,6 @@ > #include <linux/device.h> > #include <linux/cpumask.h> > #include <linux/list.h> > -#include <linux/workqueue.h> > > /** > * struct node_hmem_attrs - heterogeneous memory performance attributes > @@ -84,10 +83,6 @@ static inline void node_set_perf_attrs(unsigned int nid, > struct node { > struct device dev; > struct list_head access_list; > - > -#if defined(CONFIG_MEMORY_HOTPLUG) && defined(CONFIG_HUGETLBFS) > - struct work_struct node_work; > -#endif > #ifdef CONFIG_HMEM_REPORTING > struct list_head cache_attrs; > struct device *cache_dev; > @@ -96,7 +91,6 @@ struct node { > > struct memory_block; > extern struct node *node_devices[]; > -typedef void (*node_registration_func_t)(struct node *); > > #if defined(CONFIG_MEMORY_HOTPLUG) && defined(CONFIG_NUMA) > void register_memory_blocks_under_node(int nid, unsigned long start_pfn, > @@ -144,11 +138,6 @@ extern void unregister_memory_block_under_nodes(struct memory_block *mem_blk); > extern int register_memory_node_under_compute_node(unsigned int mem_nid, > unsigned int cpu_nid, > unsigned access); > - > -#ifdef CONFIG_HUGETLBFS > -extern void register_hugetlbfs_with_node(node_registration_func_t doregister, > - node_registration_func_t unregister); > -#endif > #else > static inline void node_dev_init(void) > { > @@ -176,11 +165,6 @@ static inline int unregister_cpu_under_node(unsigned int cpu, unsigned int nid) > static inline void unregister_memory_block_under_nodes(struct memory_block *mem_blk) > { > } > - > -static inline void register_hugetlbfs_with_node(node_registration_func_t reg, > - node_registration_func_t unreg) > -{ > -} > #endif > > #define to_node(device) container_of(device, struct node, dev) > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index 536a52c29035..9a72499486c1 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -33,6 +33,7 @@ > #include <linux/migrate.h> > #include <linux/nospec.h> > #include <linux/delayacct.h> > +#include <linux/memory.h> > > #include <asm/page.h> > #include <asm/pgalloc.h> > @@ -3967,19 +3968,19 @@ static void hugetlb_unregister_node(struct node *node) > * Register hstate attributes for a single node device. > * No-op if attributes already registered. > */ > -static void hugetlb_register_node(struct node *node) > +static int hugetlb_register_node(struct node *node) > { > struct hstate *h; > struct node_hstate *nhs = &node_hstates[node->dev.id]; > int err; > > if (nhs->hugepages_kobj) > - return; /* already allocated */ > + return 0; /* already allocated */ > > nhs->hugepages_kobj = kobject_create_and_add("hugepages", > &node->dev.kobj); > if (!nhs->hugepages_kobj) > - return; > + return -ENOMEM; > > for_each_hstate(h) { > err = hugetlb_sysfs_add_hstate(h, nhs->hugepages_kobj, > @@ -3989,9 +3990,28 @@ static void hugetlb_register_node(struct node *node) > pr_err("HugeTLB: Unable to add hstate %s for node %d\n", > h->name, node->dev.id); > hugetlb_unregister_node(node); > - break; > + return -ENOMEM; > } > } > + return 0; > +} > + > +static int __meminit hugetlb_memory_callback(struct notifier_block *self, > + unsigned long action, void *arg) > +{ > + int ret = 0; > + struct memory_notify *mnb = arg; > + int nid = mnb->status_change_nid; > + > + if (nid == NUMA_NO_NODE) > + return NOTIFY_DONE; > + > + if (action == MEM_GOING_ONLINE) > + ret = hugetlb_register_node(node_devices[nid]); > + else if (action == MEM_CANCEL_ONLINE || action == MEM_OFFLINE) > + hugetlb_unregister_node(node_devices[nid]); > + > + return notifier_from_errno(ret); > } > > /* > @@ -4003,18 +4023,11 @@ static void __init hugetlb_register_all_nodes(void) > { > int nid; > > - for_each_node_state(nid, N_MEMORY) { > - struct node *node = node_devices[nid]; > - if (node->dev.id == nid) > - hugetlb_register_node(node); > - } > - > - /* > - * Let the node device driver know we're here so it can > - * [un]register hstate attributes on node hotplug. > - */ > - register_hugetlbfs_with_node(hugetlb_register_node, > - hugetlb_unregister_node); > + get_online_mems(); > + hotplug_memory_notifier(hugetlb_memory_callback, 0); > + for_each_node_state(nid, N_MEMORY) > + hugetlb_register_node(node_devices[nid]); > + put_online_mems(); > } > #else /* !CONFIG_NUMA */ Do we really *need* the memory hotplug notifier and the added complexity due for handling memory-less nodes? Why can't we simply register/unregister sysfs entries in register_node/unregister_node and call it a day? TBH, we should just have sysfs entries for memory-less nodes and not care about such (corner) cases. -- Thanks, David / dhildenb