diff options
| -rw-r--r-- | mm/ksm.c | 55 |
1 files changed, 41 insertions, 14 deletions
@@ -226,7 +226,9 @@ static unsigned int ksm_merge_across_nodes = 1; #define KSM_RUN_STOP 0 #define KSM_RUN_MERGE 1 #define KSM_RUN_UNMERGE 2 -static unsigned int ksm_run = KSM_RUN_STOP; +#define KSM_RUN_OFFLINE 4 +static unsigned long ksm_run = KSM_RUN_STOP; +static void wait_while_offlining(void); static DECLARE_WAIT_QUEUE_HEAD(ksm_thread_wait); static DEFINE_MUTEX(ksm_thread_mutex); @@ -1700,6 +1702,7 @@ static int ksm_scan_thread(void *nothing) while (!kthread_should_stop()) { mutex_lock(&ksm_thread_mutex); + wait_while_offlining(); if (ksmd_should_run()) ksm_do_scan(ksm_thread_pages_to_scan); mutex_unlock(&ksm_thread_mutex); @@ -2056,6 +2059,22 @@ void ksm_migrate_page(struct page *newpage, struct page *oldpage) #endif /* CONFIG_MIGRATION */ #ifdef CONFIG_MEMORY_HOTREMOVE +static int just_wait(void *word) +{ + schedule(); + return 0; +} + +static void wait_while_offlining(void) +{ + while (ksm_run & KSM_RUN_OFFLINE) { + mutex_unlock(&ksm_thread_mutex); + wait_on_bit(&ksm_run, ilog2(KSM_RUN_OFFLINE), + just_wait, TASK_UNINTERRUPTIBLE); + mutex_lock(&ksm_thread_mutex); + } +} + static void ksm_check_stable_tree(unsigned long start_pfn, unsigned long end_pfn) { @@ -2098,15 +2117,15 @@ static int ksm_memory_callback(struct notifier_block *self, switch (action) { case MEM_GOING_OFFLINE: /* - * Keep it very simple for now: just lock out ksmd and - * MADV_UNMERGEABLE while any memory is going offline. - * mutex_lock_nested() is necessary because lockdep was alarmed - * that here we take ksm_thread_mutex inside notifier chain - * mutex, and later take notifier chain mutex inside - * ksm_thread_mutex to unlock it. But that's safe because both - * are inside mem_hotplug_mutex. + * Prevent ksm_do_scan(), unmerge_and_remove_all_rmap_items() + * and remove_all_stable_nodes() while memory is going offline: + * it is unsafe for them to touch the stable tree at this time. + * But unmerge_ksm_pages(), rmap lookups and other entry points + * which do not need the ksm_thread_mutex are all safe. */ - mutex_lock_nested(&ksm_thread_mutex, SINGLE_DEPTH_NESTING); + mutex_lock(&ksm_thread_mutex); + ksm_run |= KSM_RUN_OFFLINE; + mutex_unlock(&ksm_thread_mutex); break; case MEM_OFFLINE: @@ -2122,11 +2141,20 @@ static int ksm_memory_callback(struct notifier_block *self, /* fallthrough */ case MEM_CANCEL_OFFLINE: + mutex_lock(&ksm_thread_mutex); + ksm_run &= ~KSM_RUN_OFFLINE; mutex_unlock(&ksm_thread_mutex); + + smp_mb(); /* wake_up_bit advises this */ + wake_up_bit(&ksm_run, ilog2(KSM_RUN_OFFLINE)); break; } return NOTIFY_OK; } +#else +static void wait_while_offlining(void) +{ +} #endif /* CONFIG_MEMORY_HOTREMOVE */ #ifdef CONFIG_SYSFS @@ -2189,7 +2217,7 @@ KSM_ATTR(pages_to_scan); static ssize_t run_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { - return sprintf(buf, "%u\n", ksm_run); + return sprintf(buf, "%lu\n", ksm_run); } static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr, @@ -2212,6 +2240,7 @@ static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr, */ mutex_lock(&ksm_thread_mutex); + wait_while_offlining(); if (ksm_run != flags) { ksm_run = flags; if (flags & KSM_RUN_UNMERGE) { @@ -2254,6 +2283,7 @@ static ssize_t merge_across_nodes_store(struct kobject *kobj, return -EINVAL; mutex_lock(&ksm_thread_mutex); + wait_while_offlining(); if (ksm_merge_across_nodes != knob) { if (ksm_pages_shared || remove_all_stable_nodes()) err = -EBUSY; @@ -2366,10 +2396,7 @@ static int __init ksm_init(void) #endif /* CONFIG_SYSFS */ #ifdef CONFIG_MEMORY_HOTREMOVE - /* - * Choose a high priority since the callback takes ksm_thread_mutex: - * later callbacks could only be taking locks which nest within that. - */ + /* There is no significance to this priority 100 */ hotplug_memory_notifier(ksm_memory_callback, 100); #endif return 0; |