[RFC v1 5/5] mm/slab: Move kvfree_rcu() into SLAB

Uladzislau Rezki (Sony)
2024-12-10T16:40:53Z

A final move of kvfree_rcu() functionality into slab_common.c file:

- Rename kfree_rcu_batch_init() to the kvfree_rcu_init();
- Invoke the kvfree_rcu_init() function from main.c after rcu_init();
- Move the rest of functionality to the slab_common.c file;
- Fully remove kvfree_rcu() from the kernel/rcu/tree.c file;
- Remove a temporary solution to handle freeing ptrs. after GP;
- Remove "__maybe_unused" from the slab_common.c file;
- Do not export main functionality for CONFIG_TINY_RCU case.

Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
---
include/linux/slab.h | 1 +
init/main.c | 1 +
kernel/rcu/tree.c | 893 +------------------------------------------
mm/slab_common.c | 256 +++++++++++--
4 files changed, 225 insertions(+), 926 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index b35e2db7eb0e..8a2d006119f8 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -1076,5 +1076,6 @@ unsigned int kmem_cache_size(struct kmem_cache *s);
size_t kmalloc_size_roundup(size_t size);

void __init kmem_cache_init_late(void);
+void __init kvfree_rcu_init(void);

#endif /* _LINUX_SLAB_H */
diff --git a/init/main.c b/init/main.c
index c4778edae797..27d177784f3a 100644
--- a/init/main.c
+++ b/init/main.c
@@ -995,6 +995,7 @@ void start_kernel(void)
workqueue_init_early();

rcu_init();
+ kvfree_rcu_init();

/* Trace events are available after this */
trace_init();
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index ab24229dfa73..4c9c16945e3a 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -186,26 +186,6 @@ static int rcu_unlock_delay;
module_param(rcu_unlock_delay, int, 0444);
#endif

-/*
- * This rcu parameter is runtime-read-only. It reflects
- * a minimum allowed number of objects which can be cached
- * per-CPU. Object size is equal to one page. This value
- * can be changed at boot time.
- */
-static int rcu_min_cached_objs = 5;
-module_param(rcu_min_cached_objs, int, 0444);
-
-// A page shrinker can ask for pages to be freed to make them
-// available for other parts of the system. This usually happens
-// under low memory conditions, and in that case we should also
-// defer page-cache filling for a short time period.
-//
-// The default value is 5 seconds, which is long enough to reduce
-// interference with the shrinker while it asks other systems to
-// drain their caches.
-static int rcu_delay_page_cache_fill_msec = 5000;
-module_param(rcu_delay_page_cache_fill_msec, int, 0444);
-
/* Retrieve RCU kthreads priority for rcutorture */
int rcu_get_gp_kthreads_prio(void)
{
@@ -2559,19 +2539,13 @@ static void rcu_do_batch(struct rcu_data *rdp)
debug_rcu_head_unqueue(rhp);

rcu_lock_acquire(&rcu_callback_map);
+ trace_rcu_invoke_callback(rcu_state.name, rhp);

f = rhp->func;
+ debug_rcu_head_callback(rhp);
+ WRITE_ONCE(rhp->func, (rcu_callback_t)0L);
+ f(rhp);

- /* This is temporary, it will be removed when migration is over. */
- if (__is_kvfree_rcu_offset((unsigned long) f)) {
- trace_rcu_invoke_kvfree_callback("", rhp, (unsigned long) f);
- kvfree((void *) rhp - (unsigned long) f);
- } else {
- trace_rcu_invoke_callback(rcu_state.name, rhp);
- debug_rcu_head_callback(rhp);
- WRITE_ONCE(rhp->func, (rcu_callback_t)0L);
- f(rhp);
- }
rcu_lock_release(&rcu_callback_map);

/*
@@ -3197,815 +3171,6 @@ void call_rcu(struct rcu_head *head, rcu_callback_t func)
}
EXPORT_SYMBOL_GPL(call_rcu);

-/* Maximum number of jiffies to wait before draining a batch. */
-#define KFREE_DRAIN_JIFFIES (5 * HZ)
-#define KFREE_N_BATCHES 2
-#define FREE_N_CHANNELS 2
-
-/**
- * struct kvfree_rcu_bulk_data - single block to store kvfree_rcu() pointers
- * @list: List node. All blocks are linked between each other
- * @gp_snap: Snapshot of RCU state for objects placed to this bulk
- * @nr_records: Number of active pointers in the array
- * @records: Array of the kvfree_rcu() pointers
- */
-struct kvfree_rcu_bulk_data {
- struct list_head list;
- struct rcu_gp_oldstate gp_snap;
- unsigned long nr_records;
- void *records[] __counted_by(nr_records);
-};
-
-/*
- * This macro defines how many entries the "records" array
- * will contain. It is based on the fact that the size of
- * kvfree_rcu_bulk_data structure becomes exactly one page.
- */
-#define KVFREE_BULK_MAX_ENTR \
- ((PAGE_SIZE - sizeof(struct kvfree_rcu_bulk_data)) / sizeof(void *))
-
-/**
- * struct kfree_rcu_cpu_work - single batch of kfree_rcu() requests
- * @rcu_work: Let queue_rcu_work() invoke workqueue handler after grace period
- * @head_free: List of kfree_rcu() objects waiting for a grace period
- * @head_free_gp_snap: Grace-period snapshot to check for attempted premature frees.
- * @bulk_head_free: Bulk-List of kvfree_rcu() objects waiting for a grace period
- * @krcp: Pointer to @kfree_rcu_cpu structure
- */
-
-struct kfree_rcu_cpu_work {
- struct rcu_work rcu_work;
- struct rcu_head *head_free;
- struct rcu_gp_oldstate head_free_gp_snap;
- struct list_head bulk_head_free[FREE_N_CHANNELS];
- struct kfree_rcu_cpu *krcp;
-};
-
-/**
- * struct kfree_rcu_cpu - batch up kfree_rcu() requests for RCU grace period
- * @head: List of kfree_rcu() objects not yet waiting for a grace period
- * @head_gp_snap: Snapshot of RCU state for objects placed to "@head"
- * @bulk_head: Bulk-List of kvfree_rcu() objects not yet waiting for a grace period
- * @krw_arr: Array of batches of kfree_rcu() objects waiting for a grace period
- * @lock: Synchronize access to this structure
- * @monitor_work: Promote @head to @head_free after KFREE_DRAIN_JIFFIES
- * @initialized: The @rcu_work fields have been initialized
- * @head_count: Number of objects in rcu_head singular list
- * @bulk_count: Number of objects in bulk-list
- * @bkvcache:
- * A simple cache list that contains objects for reuse purpose.
- * In order to save some per-cpu space the list is singular.
- * Even though it is lockless an access has to be protected by the
- * per-cpu lock.
- * @page_cache_work: A work to refill the cache when it is empty
- * @backoff_page_cache_fill: Delay cache refills
- * @work_in_progress: Indicates that page_cache_work is running
- * @hrtimer: A hrtimer for scheduling a page_cache_work
- * @nr_bkv_objs: number of allocated objects at @bkvcache.
- *
- * This is a per-CPU structure. The reason that it is not included in
- * the rcu_data structure is to permit this code to be extracted from
- * the RCU files. Such extraction could allow further optimization of
- * the interactions with the slab allocators.
- */
-struct kfree_rcu_cpu {
- // Objects queued on a linked list
- // through their rcu_head structures.
- struct rcu_head *head;
- unsigned long head_gp_snap;
- atomic_t head_count;
-
- // Objects queued on a bulk-list.
- struct list_head bulk_head[FREE_N_CHANNELS];
- atomic_t bulk_count[FREE_N_CHANNELS];
-
- struct kfree_rcu_cpu_work krw_arr[KFREE_N_BATCHES];
- raw_spinlock_t lock;
- struct delayed_work monitor_work;
- bool initialized;
-
- struct delayed_work page_cache_work;
- atomic_t backoff_page_cache_fill;
- atomic_t work_in_progress;
- struct hrtimer hrtimer;
-
- struct llist_head bkvcache;
- int nr_bkv_objs;
-};
-
-static DEFINE_PER_CPU(struct kfree_rcu_cpu, krc) = {
- .lock = __RAW_SPIN_LOCK_UNLOCKED(krc.lock),
-};
-
-static __always_inline void
-debug_rcu_bhead_unqueue(struct kvfree_rcu_bulk_data *bhead)
-{
-#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
- int i;
-
- for (i = 0; i < bhead->nr_records; i++)
- debug_rcu_head_unqueue((struct rcu_head *)(bhead->records[i]));
-#endif
-}
-
-static inline struct kfree_rcu_cpu *
-krc_this_cpu_lock(unsigned long *flags)
-{
- struct kfree_rcu_cpu *krcp;
-
- local_irq_save(*flags); // For safely calling this_cpu_ptr().
- krcp = this_cpu_ptr(&krc);
- raw_spin_lock(&krcp->lock);
-
- return krcp;
-}
-
-static inline void
-krc_this_cpu_unlock(struct kfree_rcu_cpu *krcp, unsigned long flags)
-{
- raw_spin_unlock_irqrestore(&krcp->lock, flags);
-}
-
-static inline struct kvfree_rcu_bulk_data *
-get_cached_bnode(struct kfree_rcu_cpu *krcp)
-{
- if (!krcp->nr_bkv_objs)
- return NULL;
-
- WRITE_ONCE(krcp->nr_bkv_objs, krcp->nr_bkv_objs - 1);
- return (struct kvfree_rcu_bulk_data *)
- llist_del_first(&krcp->bkvcache);
-}
-
-static inline bool
-put_cached_bnode(struct kfree_rcu_cpu *krcp,
- struct kvfree_rcu_bulk_data *bnode)
-{
- // Check the limit.
- if (krcp->nr_bkv_objs >= rcu_min_cached_objs)
- return false;
-
- llist_add((struct llist_node *) bnode, &krcp->bkvcache);
- WRITE_ONCE(krcp->nr_bkv_objs, krcp->nr_bkv_objs + 1);
- return true;
-}
-
-static int
-drain_page_cache(struct kfree_rcu_cpu *krcp)
-{
- unsigned long flags;
- struct llist_node *page_list, *pos, *n;
- int freed = 0;
-
- if (!rcu_min_cached_objs)
- return 0;
-
- raw_spin_lock_irqsave(&krcp->lock, flags);
- page_list = llist_del_all(&krcp->bkvcache);
- WRITE_ONCE(krcp->nr_bkv_objs, 0);
- raw_spin_unlock_irqrestore(&krcp->lock, flags);
-
- llist_for_each_safe(pos, n, page_list) {
- free_page((unsigned long)pos);
- freed++;
- }
-
- return freed;
-}
-
-static void
-kvfree_rcu_bulk(struct kfree_rcu_cpu *krcp,
- struct kvfree_rcu_bulk_data *bnode, int idx)
-{
- unsigned long flags;
- int i;
-
- if (!WARN_ON_ONCE(!poll_state_synchronize_rcu_full(&bnode->gp_snap))) {
- debug_rcu_bhead_unqueue(bnode);
- rcu_lock_acquire(&rcu_callback_map);
- if (idx == 0) { // kmalloc() / kfree().
- trace_rcu_invoke_kfree_bulk_callback(
- rcu_state.name, bnode->nr_records,
- bnode->records);
-
- kfree_bulk(bnode->nr_records, bnode->records);
- } else { // vmalloc() / vfree().
- for (i = 0; i < bnode->nr_records; i++) {
- trace_rcu_invoke_kvfree_callback(
- rcu_state.name, bnode->records[i], 0);
-
- vfree(bnode->records[i]);
- }
- }
- rcu_lock_release(&rcu_callback_map);
- }
-
- raw_spin_lock_irqsave(&krcp->lock, flags);
- if (put_cached_bnode(krcp, bnode))
- bnode = NULL;
- raw_spin_unlock_irqrestore(&krcp->lock, flags);
-
- if (bnode)
- free_page((unsigned long) bnode);
-
- cond_resched_tasks_rcu_qs();
-}
-
-static void
-kvfree_rcu_list(struct rcu_head *head)
-{
- struct rcu_head *next;
-
- for (; head; head = next) {
- void *ptr = (void *) head->func;
- unsigned long offset = (void *) head - ptr;
-
- next = head->next;
- debug_rcu_head_unqueue((struct rcu_head *)ptr);
- rcu_lock_acquire(&rcu_callback_map);
- trace_rcu_invoke_kvfree_callback(rcu_state.name, head, offset);
-
- if (!WARN_ON_ONCE(!__is_kvfree_rcu_offset(offset)))
- kvfree(ptr);
-
- rcu_lock_release(&rcu_callback_map);
- cond_resched_tasks_rcu_qs();
- }
-}
-
-/*
- * This function is invoked in workqueue context after a grace period.
- * It frees all the objects queued on ->bulk_head_free or ->head_free.
- */
-static void kfree_rcu_work(struct work_struct *work)
-{
- unsigned long flags;
- struct kvfree_rcu_bulk_data *bnode, *n;
- struct list_head bulk_head[FREE_N_CHANNELS];
- struct rcu_head *head;
- struct kfree_rcu_cpu *krcp;
- struct kfree_rcu_cpu_work *krwp;
- struct rcu_gp_oldstate head_gp_snap;
- int i;
-
- krwp = container_of(to_rcu_work(work),
- struct kfree_rcu_cpu_work, rcu_work);
- krcp = krwp->krcp;
-
- raw_spin_lock_irqsave(&krcp->lock, flags);
- // Channels 1 and 2.
- for (i = 0; i < FREE_N_CHANNELS; i++)
- list_replace_init(&krwp->bulk_head_free[i], &bulk_head[i]);
-
- // Channel 3.
- head = krwp->head_free;
- krwp->head_free = NULL;
- head_gp_snap = krwp->head_free_gp_snap;
- raw_spin_unlock_irqrestore(&krcp->lock, flags);
-
- // Handle the first two channels.
- for (i = 0; i < FREE_N_CHANNELS; i++) {
- // Start from the tail page, so a GP is likely passed for it.
- list_for_each_entry_safe(bnode, n, &bulk_head[i], list)
- kvfree_rcu_bulk(krcp, bnode, i);
- }
-
- /*
- * This is used when the "bulk" path can not be used for the
- * double-argument of kvfree_rcu(). This happens when the
- * page-cache is empty, which means that objects are instead
- * queued on a linked list through their rcu_head structures.
- * This list is named "Channel 3".
- */
- if (head && !WARN_ON_ONCE(!poll_state_synchronize_rcu_full(&head_gp_snap)))
- kvfree_rcu_list(head);
-}
-
-static bool
-need_offload_krc(struct kfree_rcu_cpu *krcp)
-{
- int i;
-
- for (i = 0; i < FREE_N_CHANNELS; i++)
- if (!list_empty(&krcp->bulk_head[i]))
- return true;
-
- return !!READ_ONCE(krcp->head);
-}
-
-static bool
-need_wait_for_krwp_work(struct kfree_rcu_cpu_work *krwp)
-{
- int i;
-
- for (i = 0; i < FREE_N_CHANNELS; i++)
- if (!list_empty(&krwp->bulk_head_free[i]))
- return true;
-
- return !!krwp->head_free;
-}
-
-static int krc_count(struct kfree_rcu_cpu *krcp)
-{
- int sum = atomic_read(&krcp->head_count);
- int i;
-
- for (i = 0; i < FREE_N_CHANNELS; i++)
- sum += atomic_read(&krcp->bulk_count[i]);
-
- return sum;
-}
-
-static void
-schedule_delayed_monitor_work(struct kfree_rcu_cpu *krcp)
-{
- long delay, delay_left;
-
- delay = krc_count(krcp) >= KVFREE_BULK_MAX_ENTR ? 1:KFREE_DRAIN_JIFFIES;
- if (delayed_work_pending(&krcp->monitor_work)) {
- delay_left = krcp->monitor_work.timer.expires - jiffies;
- if (delay < delay_left)
- mod_delayed_work(system_unbound_wq, &krcp->monitor_work, delay);
- return;
- }
- queue_delayed_work(system_unbound_wq, &krcp->monitor_work, delay);
-}
-
-static void
-kvfree_rcu_drain_ready(struct kfree_rcu_cpu *krcp)
-{
- struct list_head bulk_ready[FREE_N_CHANNELS];
- struct kvfree_rcu_bulk_data *bnode, *n;
- struct rcu_head *head_ready = NULL;
- unsigned long flags;
- int i;
-
- raw_spin_lock_irqsave(&krcp->lock, flags);
- for (i = 0; i < FREE_N_CHANNELS; i++) {
- INIT_LIST_HEAD(&bulk_ready[i]);
-
- list_for_each_entry_safe_reverse(bnode, n, &krcp->bulk_head[i], list) {
- if (!poll_state_synchronize_rcu_full(&bnode->gp_snap))
- break;
-
- atomic_sub(bnode->nr_records, &krcp->bulk_count[i]);
- list_move(&bnode->list, &bulk_ready[i]);
- }
- }
-
- if (krcp->head && poll_state_synchronize_rcu(krcp->head_gp_snap)) {
- head_ready = krcp->head;
- atomic_set(&krcp->head_count, 0);
- WRITE_ONCE(krcp->head, NULL);
- }
- raw_spin_unlock_irqrestore(&krcp->lock, flags);
-
- for (i = 0; i < FREE_N_CHANNELS; i++) {
- list_for_each_entry_safe(bnode, n, &bulk_ready[i], list)
- kvfree_rcu_bulk(krcp, bnode, i);
- }
-
- if (head_ready)
- kvfree_rcu_list(head_ready);
-}
-
-/*
- * Return: %true if a work is queued, %false otherwise.
- */
-static bool
-kvfree_rcu_queue_batch(struct kfree_rcu_cpu *krcp)
-{
- unsigned long flags;
- bool queued = false;
- int i, j;
-
- raw_spin_lock_irqsave(&krcp->lock, flags);
-
- // Attempt to start a new batch.
- for (i = 0; i < KFREE_N_BATCHES; i++) {
- struct kfree_rcu_cpu_work *krwp = &(krcp->krw_arr[i]);
-
- // Try to detach bulk_head or head and attach it, only when
- // all channels are free. Any channel is not free means at krwp
- // there is on-going rcu work to handle krwp's free business.
- if (need_wait_for_krwp_work(krwp))
- continue;
-
- // kvfree_rcu_drain_ready() might handle this krcp, if so give up.
- if (need_offload_krc(krcp)) {
- // Channel 1 corresponds to the SLAB-pointer bulk path.
- // Channel 2 corresponds to vmalloc-pointer bulk path.
- for (j = 0; j < FREE_N_CHANNELS; j++) {
- if (list_empty(&krwp->bulk_head_free[j])) {
- atomic_set(&krcp->bulk_count[j], 0);
- list_replace_init(&krcp->bulk_head[j],
- &krwp->bulk_head_free[j]);
- }
- }
-
- // Channel 3 corresponds to both SLAB and vmalloc
- // objects queued on the linked list.
- if (!krwp->head_free) {
- krwp->head_free = krcp->head;
- get_state_synchronize_rcu_full(&krwp->head_free_gp_snap);
- atomic_set(&krcp->head_count, 0);
- WRITE_ONCE(krcp->head, NULL);
- }
-
- // One work is per one batch, so there are three
- // "free channels", the batch can handle. Break
- // the loop since it is done with this CPU thus
- // queuing an RCU work is _always_ success here.
- queued = queue_rcu_work(system_unbound_wq, &krwp->rcu_work);
- WARN_ON_ONCE(!queued);
- break;
- }
- }
-
- raw_spin_unlock_irqrestore(&krcp->lock, flags);
- return queued;
-}
-
-/*
- * This function is invoked after the KFREE_DRAIN_JIFFIES timeout.
- */
-static void kfree_rcu_monitor(struct work_struct *work)
-{
- struct kfree_rcu_cpu *krcp = container_of(work,
- struct kfree_rcu_cpu, monitor_work.work);
-
- // Drain ready for reclaim.
- kvfree_rcu_drain_ready(krcp);
-
- // Queue a batch for a rest.
- kvfree_rcu_queue_batch(krcp);
-
- // If there is nothing to detach, it means that our job is
- // successfully done here. In case of having at least one
- // of the channels that is still busy we should rearm the
- // work to repeat an attempt. Because previous batches are
- // still in progress.
- if (need_offload_krc(krcp))
- schedule_delayed_monitor_work(krcp);
-}
-
-static enum hrtimer_restart
-schedule_page_work_fn(struct hrtimer *t)
-{
- struct kfree_rcu_cpu *krcp =
- container_of(t, struct kfree_rcu_cpu, hrtimer);
-
- queue_delayed_work(system_highpri_wq, &krcp->page_cache_work, 0);
- return HRTIMER_NORESTART;
-}
-
-static void fill_page_cache_func(struct work_struct *work)
-{
- struct kvfree_rcu_bulk_data *bnode;
- struct kfree_rcu_cpu *krcp =
- container_of(work, struct kfree_rcu_cpu,
- page_cache_work.work);
- unsigned long flags;
- int nr_pages;
- bool pushed;
- int i;
-
- nr_pages = atomic_read(&krcp->backoff_page_cache_fill) ?
- 1 : rcu_min_cached_objs;
-
- for (i = READ_ONCE(krcp->nr_bkv_objs); i < nr_pages; i++) {
- bnode = (struct kvfree_rcu_bulk_data *)
- __get_free_page(GFP_KERNEL | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
-
- if (!bnode)
- break;
-
- raw_spin_lock_irqsave(&krcp->lock, flags);
- pushed = put_cached_bnode(krcp, bnode);
- raw_spin_unlock_irqrestore(&krcp->lock, flags);
-
- if (!pushed) {
- free_page((unsigned long) bnode);
- break;
- }
- }
-
- atomic_set(&krcp->work_in_progress, 0);
- atomic_set(&krcp->backoff_page_cache_fill, 0);
-}
-
-static void
-run_page_cache_worker(struct kfree_rcu_cpu *krcp)
-{
- // If cache disabled, bail out.
- if (!rcu_min_cached_objs)
- return;
-
- if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING &&
- !atomic_xchg(&krcp->work_in_progress, 1)) {
- if (atomic_read(&krcp->backoff_page_cache_fill)) {
- queue_delayed_work(system_unbound_wq,
- &krcp->page_cache_work,
- msecs_to_jiffies(rcu_delay_page_cache_fill_msec));
- } else {
- hrtimer_init(&krcp->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
- krcp->hrtimer.function = schedule_page_work_fn;
- hrtimer_start(&krcp->hrtimer, 0, HRTIMER_MODE_REL);
- }
- }
-}
-
-// Record ptr in a page managed by krcp, with the pre-krc_this_cpu_lock()
-// state specified by flags. If can_alloc is true, the caller must
-// be schedulable and not be holding any locks or mutexes that might be
-// acquired by the memory allocator or anything that it might invoke.
-// Returns true if ptr was successfully recorded, else the caller must
-// use a fallback.
-static inline bool
-add_ptr_to_bulk_krc_lock(struct kfree_rcu_cpu **krcp,
- unsigned long *flags, void *ptr, bool can_alloc)
-{
- struct kvfree_rcu_bulk_data *bnode;
- int idx;
-
- *krcp = krc_this_cpu_lock(flags);
- if (unlikely(!(*krcp)->initialized))
- return false;
-
- idx = !!is_vmalloc_addr(ptr);
- bnode = list_first_entry_or_null(&(*krcp)->bulk_head[idx],
- struct kvfree_rcu_bulk_data, list);
-
- /* Check if a new block is required. */
- if (!bnode || bnode->nr_records == KVFREE_BULK_MAX_ENTR) {
- bnode = get_cached_bnode(*krcp);
- if (!bnode && can_alloc) {
- krc_this_cpu_unlock(*krcp, *flags);
-
- // __GFP_NORETRY - allows a light-weight direct reclaim
- // what is OK from minimizing of fallback hitting point of
- // view. Apart of that it forbids any OOM invoking what is
- // also beneficial since we are about to release memory soon.
- //
- // __GFP_NOMEMALLOC - prevents from consuming of all the
- // memory reserves. Please note we have a fallback path.
- //
- // __GFP_NOWARN - it is supposed that an allocation can
- // be failed under low memory or high memory pressure
- // scenarios.
- bnode = (struct kvfree_rcu_bulk_data *)
- __get_free_page(GFP_KERNEL | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
- raw_spin_lock_irqsave(&(*krcp)->lock, *flags);
- }
-
- if (!bnode)
- return false;
-
- // Initialize the new block and attach it.
- bnode->nr_records = 0;
- list_add(&bnode->list, &(*krcp)->bulk_head[idx]);
- }
-
- // Finally insert and update the GP for this page.
- bnode->nr_records++;
- bnode->records[bnode->nr_records - 1] = ptr;
- get_state_synchronize_rcu_full(&bnode->gp_snap);
- atomic_inc(&(*krcp)->bulk_count[idx]);
-
- return true;
-}
-
-/*
- * Queue a request for lazy invocation of the appropriate free routine
- * after a grace period. Please note that three paths are maintained,
- * two for the common case using arrays of pointers and a third one that
- * is used only when the main paths cannot be used, for example, due to
- * memory pressure.
- *
- * Each kvfree_call_rcu() request is added to a batch. The batch will be drained
- * every KFREE_DRAIN_JIFFIES number of jiffies. All the objects in the batch will
- * be free'd in workqueue context. This allows us to: batch requests together to
- * reduce the number of grace periods during heavy kfree_rcu()/kvfree_rcu() load.
- */
-void kvfree_call_rcu(struct rcu_head *head, void *ptr)
-{
- unsigned long flags;
- struct kfree_rcu_cpu *krcp;
- bool success;
-
- if (head) {
- call_rcu(head, (rcu_callback_t) ((void *) head - ptr));
- } else {
- synchronize_rcu();
- kvfree(ptr);
- }
-
- /* Disconnect the rest. */
- return;
-
- /*
- * Please note there is a limitation for the head-less
- * variant, that is why there is a clear rule for such
- * objects: it can be used from might_sleep() context
- * only. For other places please embed an rcu_head to
- * your data.
- */
- if (!head)
- might_sleep();
-
- // Queue the object but don't yet schedule the batch.
- if (debug_rcu_head_queue(ptr)) {
- // Probable double kfree_rcu(), just leak.
- WARN_ONCE(1, "%s(): Double-freed call. rcu_head %p\n",
- __func__, head);
-
- // Mark as success and leave.
- return;
- }
-
- kasan_record_aux_stack_noalloc(ptr);
- success = add_ptr_to_bulk_krc_lock(&krcp, &flags, ptr, !head);
- if (!success) {
- run_page_cache_worker(krcp);
-
- if (head == NULL)
- // Inline if kvfree_rcu(one_arg) call.
- goto unlock_return;
-
- head->func = ptr;
- head->next = krcp->head;
- WRITE_ONCE(krcp->head, head);
- atomic_inc(&krcp->head_count);
-
- // Take a snapshot for this krcp.
- krcp->head_gp_snap = get_state_synchronize_rcu();
- success = true;
- }
-
- /*
- * The kvfree_rcu() caller considers the pointer freed at this point
- * and likely removes any references to it. Since the actual slab
- * freeing (and kmemleak_free()) is deferred, tell kmemleak to ignore
- * this object (no scanning or false positives reporting).
- */
- kmemleak_ignore(ptr);
-
- // Set timer to drain after KFREE_DRAIN_JIFFIES.
- if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING)
- schedule_delayed_monitor_work(krcp);
-
-unlock_return:
- krc_this_cpu_unlock(krcp, flags);
-
- /*
- * Inline kvfree() after synchronize_rcu(). We can do
- * it from might_sleep() context only, so the current
- * CPU can pass the QS state.
- */
- if (!success) {
- debug_rcu_head_unqueue((struct rcu_head *) ptr);
- synchronize_rcu();
- kvfree(ptr);
- }
-}
-EXPORT_SYMBOL_GPL(kvfree_call_rcu);
-
-/**
- * kvfree_rcu_barrier - Wait until all in-flight kvfree_rcu() complete.
- *
- * Note that a single argument of kvfree_rcu() call has a slow path that
- * triggers synchronize_rcu() following by freeing a pointer. It is done
- * before the return from the function. Therefore for any single-argument
- * call that will result in a kfree() to a cache that is to be destroyed
- * during module exit, it is developer's responsibility to ensure that all
- * such calls have returned before the call to kmem_cache_destroy().
- */
-void kvfree_rcu_barrier(void)
-{
- struct kfree_rcu_cpu_work *krwp;
- struct kfree_rcu_cpu *krcp;
- bool queued;
- int i, cpu;
-
- /* Temporary. */
- rcu_barrier();
-
- /*
- * Firstly we detach objects and queue them over an RCU-batch
- * for all CPUs. Finally queued works are flushed for each CPU.
- *
- * Please note. If there are outstanding batches for a particular
- * CPU, those have to be finished first following by queuing a new.
- */
- for_each_possible_cpu(cpu) {
- krcp = per_cpu_ptr(&krc, cpu);
-
- /*
- * Check if this CPU has any objects which have been queued for a
- * new GP completion. If not(means nothing to detach), we are done
- * with it. If any batch is pending/running for this "krcp", below
- * per-cpu flush_rcu_work() waits its completion(see last step).
- */
- if (!need_offload_krc(krcp))
- continue;
-
- while (1) {
- /*
- * If we are not able to queue a new RCU work it means:
- * - batches for this CPU are still in flight which should
- * be flushed first and then repeat;
- * - no objects to detach, because of concurrency.
- */
- queued = kvfree_rcu_queue_batch(krcp);
-
- /*
- * Bail out, if there is no need to offload this "krcp"
- * anymore. As noted earlier it can run concurrently.
- */
- if (queued || !need_offload_krc(krcp))
- break;
-
- /* There are ongoing batches. */
- for (i = 0; i < KFREE_N_BATCHES; i++) {
- krwp = &(krcp->krw_arr[i]);
- flush_rcu_work(&krwp->rcu_work);
- }
- }
- }
-
- /*
- * Now we guarantee that all objects are flushed.
- */
- for_each_possible_cpu(cpu) {
- krcp = per_cpu_ptr(&krc, cpu);
-
- /*
- * A monitor work can drain ready to reclaim objects
- * directly. Wait its completion if running or pending.
- */
- cancel_delayed_work_sync(&krcp->monitor_work);
-
- for (i = 0; i < KFREE_N_BATCHES; i++) {
- krwp = &(krcp->krw_arr[i]);
- flush_rcu_work(&krwp->rcu_work);
- }
- }
-}
-EXPORT_SYMBOL_GPL(kvfree_rcu_barrier);
-
-static unsigned long
-kfree_rcu_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
-{
- int cpu;
- unsigned long count = 0;
-
- /* Snapshot count of all CPUs */
- for_each_possible_cpu(cpu) {
- struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
-
- count += krc_count(krcp);
- count += READ_ONCE(krcp->nr_bkv_objs);
- atomic_set(&krcp->backoff_page_cache_fill, 1);
- }
-
- return count == 0 ? SHRINK_EMPTY : count;
-}
-
-static unsigned long
-kfree_rcu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
-{
- int cpu, freed = 0;
-
- for_each_possible_cpu(cpu) {
- int count;
- struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
-
- count = krc_count(krcp);
- count += drain_page_cache(krcp);
- kfree_rcu_monitor(&krcp->monitor_work.work);
-
- sc->nr_to_scan -= count;
- freed += count;
-
- if (sc->nr_to_scan <= 0)
- break;
- }
-
- return freed == 0 ? SHRINK_STOP : freed;
-}
-
-void __init kfree_rcu_scheduler_running(void)
-{
- int cpu;
-
- for_each_possible_cpu(cpu) {
- struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
-
- if (need_offload_krc(krcp))
- schedule_delayed_monitor_work(krcp);
- }
-}
-
/*
* During early boot, any blocking grace-period wait automatically
* implies a grace period.
@@ -5665,62 +4830,12 @@ static void __init rcu_dump_rcu_node_tree(void)

struct workqueue_struct *rcu_gp_wq;

-static void __init kfree_rcu_batch_init(void)
-{
- int cpu;
- int i, j;
- struct shrinker *kfree_rcu_shrinker;
-
- /* Clamp it to [0:100] seconds interval. */
- if (rcu_delay_page_cache_fill_msec < 0 ||
- rcu_delay_page_cache_fill_msec > 100 * MSEC_PER_SEC) {
-
- rcu_delay_page_cache_fill_msec =
- clamp(rcu_delay_page_cache_fill_msec, 0,
- (int) (100 * MSEC_PER_SEC));
-
- pr_info("Adjusting rcutree.rcu_delay_page_cache_fill_msec to %d ms.\n",
- rcu_delay_page_cache_fill_msec);
- }
-
- for_each_possible_cpu(cpu) {
- struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
-
- for (i = 0; i < KFREE_N_BATCHES; i++) {
- INIT_RCU_WORK(&krcp->krw_arr[i].rcu_work, kfree_rcu_work);
- krcp->krw_arr[i].krcp = krcp;
-
- for (j = 0; j < FREE_N_CHANNELS; j++)
- INIT_LIST_HEAD(&krcp->krw_arr[i].bulk_head_free[j]);
- }
-
- for (i = 0; i < FREE_N_CHANNELS; i++)
- INIT_LIST_HEAD(&krcp->bulk_head[i]);
-
- INIT_DELAYED_WORK(&krcp->monitor_work, kfree_rcu_monitor);
- INIT_DELAYED_WORK(&krcp->page_cache_work, fill_page_cache_func);
- krcp->initialized = true;
- }
-
- kfree_rcu_shrinker = shrinker_alloc(0, "rcu-kfree");
- if (!kfree_rcu_shrinker) {
- pr_err("Failed to allocate kfree_rcu() shrinker!\n");
- return;
- }
-
- kfree_rcu_shrinker->count_objects = kfree_rcu_shrink_count;
- kfree_rcu_shrinker->scan_objects = kfree_rcu_shrink_scan;
-
- shrinker_register(kfree_rcu_shrinker);
-}
-
void __init rcu_init(void)
{
int cpu = smp_processor_id();

rcu_early_boot_tests();

- kfree_rcu_batch_init();
rcu_bootup_announce();
sanitize_kthread_prio();
rcu_init_geometry();
diff --git a/mm/slab_common.c b/mm/slab_common.c
index cffc96bd279a..39de00e2cf88 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -1513,7 +1513,7 @@ put_cached_bnode(struct kfree_rcu_cpu *krcp,
return true;
}

-static int __maybe_unused
+static int
drain_page_cache(struct kfree_rcu_cpu *krcp)
{
unsigned long flags;
@@ -1600,7 +1600,7 @@ kvfree_rcu_list(struct rcu_head *head)
* This function is invoked in workqueue context after a grace period.
* It frees all the objects queued on ->bulk_head_free or ->head_free.
*/
-static void __maybe_unused
+static void
kfree_rcu_work(struct work_struct *work)
{
unsigned long flags;
@@ -1793,7 +1793,7 @@ kvfree_rcu_queue_batch(struct kfree_rcu_cpu *krcp)
/*
* This function is invoked after the KFREE_DRAIN_JIFFIES timeout.
*/
-static void __maybe_unused
+static void
kfree_rcu_monitor(struct work_struct *work)
{
struct kfree_rcu_cpu *krcp = container_of(work,
@@ -1814,17 +1814,7 @@ kfree_rcu_monitor(struct work_struct *work)
schedule_delayed_monitor_work(krcp);
}

-static enum hrtimer_restart
-schedule_page_work_fn(struct hrtimer *t)
-{
- struct kfree_rcu_cpu *krcp =
- container_of(t, struct kfree_rcu_cpu, hrtimer);
-
- queue_delayed_work(system_highpri_wq, &krcp->page_cache_work, 0);
- return HRTIMER_NORESTART;
-}
-
-static void __maybe_unused
+static void
fill_page_cache_func(struct work_struct *work)
{
struct kvfree_rcu_bulk_data *bnode;
@@ -1860,27 +1850,6 @@ fill_page_cache_func(struct work_struct *work)
atomic_set(&krcp->backoff_page_cache_fill, 0);
}

-static void __maybe_unused
-run_page_cache_worker(struct kfree_rcu_cpu *krcp)
-{
- // If cache disabled, bail out.
- if (!rcu_min_cached_objs)
- return;
-
- if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING &&
- !atomic_xchg(&krcp->work_in_progress, 1)) {
- if (atomic_read(&krcp->backoff_page_cache_fill)) {
- queue_delayed_work(system_unbound_wq,
- &krcp->page_cache_work,
- msecs_to_jiffies(rcu_delay_page_cache_fill_msec));
- } else {
- hrtimer_init(&krcp->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
- krcp->hrtimer.function = schedule_page_work_fn;
- hrtimer_start(&krcp->hrtimer, 0, HRTIMER_MODE_REL);
- }
- }
-}
-
// Record ptr in a page managed by krcp, with the pre-krc_this_cpu_lock()
// state specified by flags. If can_alloc is true, the caller must
// be schedulable and not be holding any locks or mutexes that might be
@@ -1941,6 +1910,219 @@ add_ptr_to_bulk_krc_lock(struct kfree_rcu_cpu **krcp,
return true;
}

+#if !defined(CONFIG_TINY_RCU)
+
+static enum hrtimer_restart
+schedule_page_work_fn(struct hrtimer *t)
+{
+ struct kfree_rcu_cpu *krcp =
+ container_of(t, struct kfree_rcu_cpu, hrtimer);
+
+ queue_delayed_work(system_highpri_wq, &krcp->page_cache_work, 0);
+ return HRTIMER_NORESTART;
+}
+
+static void
+run_page_cache_worker(struct kfree_rcu_cpu *krcp)
+{
+ // If cache disabled, bail out.
+ if (!rcu_min_cached_objs)
+ return;
+
+ if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING &&
+ !atomic_xchg(&krcp->work_in_progress, 1)) {
+ if (atomic_read(&krcp->backoff_page_cache_fill)) {
+ queue_delayed_work(system_unbound_wq,
+ &krcp->page_cache_work,
+ msecs_to_jiffies(rcu_delay_page_cache_fill_msec));
+ } else {
+ hrtimer_init(&krcp->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+ krcp->hrtimer.function = schedule_page_work_fn;
+ hrtimer_start(&krcp->hrtimer, 0, HRTIMER_MODE_REL);
+ }
+ }
+}
+
+/*
+ * Queue a request for lazy invocation of the appropriate free routine
+ * after a grace period. Please note that three paths are maintained,
+ * two for the common case using arrays of pointers and a third one that
+ * is used only when the main paths cannot be used, for example, due to
+ * memory pressure.
+ *
+ * Each kvfree_call_rcu() request is added to a batch. The batch will be drained
+ * every KFREE_DRAIN_JIFFIES number of jiffies. All the objects in the batch will
+ * be free'd in workqueue context. This allows us to: batch requests together to
+ * reduce the number of grace periods during heavy kfree_rcu()/kvfree_rcu() load.
+ */
+void kvfree_call_rcu(struct rcu_head *head, void *ptr)
+{
+ unsigned long flags;
+ struct kfree_rcu_cpu *krcp;
+ bool success;
+
+ /*
+ * Please note there is a limitation for the head-less
+ * variant, that is why there is a clear rule for such
+ * objects: it can be used from might_sleep() context
+ * only. For other places please embed an rcu_head to
+ * your data.
+ */
+ if (!head)
+ might_sleep();
+
+ // Queue the object but don't yet schedule the batch.
+ if (debug_rcu_head_queue(ptr)) {
+ // Probable double kfree_rcu(), just leak.
+ WARN_ONCE(1, "%s(): Double-freed call. rcu_head %p\n",
+ __func__, head);
+
+ // Mark as success and leave.
+ return;
+ }
+
+ kasan_record_aux_stack_noalloc(ptr);
+ success = add_ptr_to_bulk_krc_lock(&krcp, &flags, ptr, !head);
+ if (!success) {
+ run_page_cache_worker(krcp);
+
+ if (head == NULL)
+ // Inline if kvfree_rcu(one_arg) call.
+ goto unlock_return;
+
+ head->func = ptr;
+ head->next = krcp->head;
+ WRITE_ONCE(krcp->head, head);
+ atomic_inc(&krcp->head_count);
+
+ // Take a snapshot for this krcp.
+ krcp->head_gp_snap = get_state_synchronize_rcu();
+ success = true;
+ }
+
+ /*
+ * The kvfree_rcu() caller considers the pointer freed at this point
+ * and likely removes any references to it. Since the actual slab
+ * freeing (and kmemleak_free()) is deferred, tell kmemleak to ignore
+ * this object (no scanning or false positives reporting).
+ */
+ kmemleak_ignore(ptr);
+
+ // Set timer to drain after KFREE_DRAIN_JIFFIES.
+ if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING)
+ schedule_delayed_monitor_work(krcp);
+
+unlock_return:
+ krc_this_cpu_unlock(krcp, flags);
+
+ /*
+ * Inline kvfree() after synchronize_rcu(). We can do
+ * it from might_sleep() context only, so the current
+ * CPU can pass the QS state.
+ */
+ if (!success) {
+ debug_rcu_head_unqueue((struct rcu_head *) ptr);
+ synchronize_rcu();
+ kvfree(ptr);
+ }
+}
+EXPORT_SYMBOL_GPL(kvfree_call_rcu);
+
+void __init
+kfree_rcu_scheduler_running(void)
+{
+ int cpu;
+
+ for_each_possible_cpu(cpu) {
+ struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
+
+ if (need_offload_krc(krcp))
+ schedule_delayed_monitor_work(krcp);
+ }
+}
+
+/**
+ * kvfree_rcu_barrier - Wait until all in-flight kvfree_rcu() complete.
+ *
+ * Note that a single argument of kvfree_rcu() call has a slow path that
+ * triggers synchronize_rcu() following by freeing a pointer. It is done
+ * before the return from the function. Therefore for any single-argument
+ * call that will result in a kfree() to a cache that is to be destroyed
+ * during module exit, it is developer's responsibility to ensure that all
+ * such calls have returned before the call to kmem_cache_destroy().
+ */
+void kvfree_rcu_barrier(void)
+{
+ struct kfree_rcu_cpu_work *krwp;
+ struct kfree_rcu_cpu *krcp;
+ bool queued;
+ int i, cpu;
+
+ /*
+ * Firstly we detach objects and queue them over an RCU-batch
+ * for all CPUs. Finally queued works are flushed for each CPU.
+ *
+ * Please note. If there are outstanding batches for a particular
+ * CPU, those have to be finished first following by queuing a new.
+ */
+ for_each_possible_cpu(cpu) {
+ krcp = per_cpu_ptr(&krc, cpu);
+
+ /*
+ * Check if this CPU has any objects which have been queued for a
+ * new GP completion. If not(means nothing to detach), we are done
+ * with it. If any batch is pending/running for this "krcp", below
+ * per-cpu flush_rcu_work() waits its completion(see last step).
+ */
+ if (!need_offload_krc(krcp))
+ continue;
+
+ while (1) {
+ /*
+ * If we are not able to queue a new RCU work it means:
+ * - batches for this CPU are still in flight which should
+ * be flushed first and then repeat;
+ * - no objects to detach, because of concurrency.
+ */
+ queued = kvfree_rcu_queue_batch(krcp);
+
+ /*
+ * Bail out, if there is no need to offload this "krcp"
+ * anymore. As noted earlier it can run concurrently.
+ */
+ if (queued || !need_offload_krc(krcp))
+ break;
+
+ /* There are ongoing batches. */
+ for (i = 0; i < KFREE_N_BATCHES; i++) {
+ krwp = &(krcp->krw_arr[i]);
+ flush_rcu_work(&krwp->rcu_work);
+ }
+ }
+ }
+
+ /*
+ * Now we guarantee that all objects are flushed.
+ */
+ for_each_possible_cpu(cpu) {
+ krcp = per_cpu_ptr(&krc, cpu);
+
+ /*
+ * A monitor work can drain ready to reclaim objects
+ * directly. Wait its completion if running or pending.
+ */
+ cancel_delayed_work_sync(&krcp->monitor_work);
+
+ for (i = 0; i < KFREE_N_BATCHES; i++) {
+ krwp = &(krcp->krw_arr[i]);
+ flush_rcu_work(&krwp->rcu_work);
+ }
+ }
+}
+EXPORT_SYMBOL_GPL(kvfree_rcu_barrier);
+
+#endif /* #if !defined(CONFIG_TINY_RCU) */
+
static unsigned long
kfree_rcu_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
{
@@ -1982,8 +2164,8 @@ kfree_rcu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
return freed == 0 ? SHRINK_STOP : freed;
}

-static void __init __maybe_unused
-kfree_rcu_batch_init(void)
+void __init
+kvfree_rcu_init(void)
{
int cpu;
int i, j;
--
2.39.5