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mm/slab: Move kvfree_rcu() into SLAB

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Move kvfree_rcu() functionality to the slab_common.c file.

Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
This commit is contained in:
Uladzislau Rezki (Sony) 2024-12-12 19:02:08 +01:00 committed by Vlastimil Babka
parent 4e67a04bfb
commit c44d336ad5
4 changed files with 881 additions and 880 deletions
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1
include/linux/rcupdate.h
View File

@ -118,7 +118,6 @@ static inline void call_rcu_hurry(struct rcu_head *head, rcu_callback_t func)
/* Internal to kernel */
void rcu_init(void);
void __init kvfree_rcu_init(void);
extern int rcu_scheduler_active;
void rcu_sched_clock_irq(int user);

1
include/linux/slab.h
View File

@ -1099,5 +1099,6 @@ 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 */

879
kernel/rcu/tree.c
View File

@ -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)
{
@ -3191,816 +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(
"slab", 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(
"slab", 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("slab", 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
schedule_delayed_monitor_work(struct kfree_rcu_cpu *krcp)
{
unsigned long flags;
raw_spin_lock_irqsave(&krcp->lock, flags);
__schedule_delayed_monitor_work(krcp);
raw_spin_unlock_irqrestore(&krcp->lock, flags);
}
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 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);
}
// 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;
}
#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);
}
}
}
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);
}
}
/*
* 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);
/**
* 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)
{
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;
}
/*
* During early boot, any blocking grace-period wait automatically
* implies a grace period.
@ -5652,55 +4822,6 @@ static void __init rcu_dump_rcu_node_tree(void)
struct workqueue_struct *rcu_gp_wq;
void __init kvfree_rcu_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, "slab-kvfree-rcu");
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();

880
mm/slab_common.c
View File

@ -28,7 +28,9 @@
#include <asm/page.h>
#include <linux/memcontrol.h>
#include <linux/stackdepot.h>
#include <trace/events/rcu.h>
#include "../kernel/rcu/rcu.h"
#include "internal.h"
#include "slab.h"
@ -1282,3 +1284,881 @@ EXPORT_TRACEPOINT_SYMBOL(kmem_cache_alloc);
EXPORT_TRACEPOINT_SYMBOL(kfree);
EXPORT_TRACEPOINT_SYMBOL(kmem_cache_free);
/*
* 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);
/* 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(
"slab", 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(
"slab", 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("slab", 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
schedule_delayed_monitor_work(struct kfree_rcu_cpu *krcp)
{
unsigned long flags;
raw_spin_lock_irqsave(&krcp->lock, flags);
__schedule_delayed_monitor_work(krcp);
raw_spin_unlock_irqrestore(&krcp->lock, flags);
}
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 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);
}
// 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;
}
#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);
}
}
}
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);
}
}
/*
* 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);
/**
* 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)
{
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 kvfree_rcu_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, "slab-kvfree-rcu");
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);
}