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Date: Wed, 4 Jan 2023 16:24:42 -0800
From: "Paul E. McKenney" <paulmck@...nel.org>
To: rcu@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, kernel-team@...a.com,
rostedt@...dmis.org, "Uladzislau Rezki (Sony)" <urezki@...il.com>,
"Paul E . McKenney" <paulmck@...nel.org>
Subject: [PATCH rcu 2/8] rcu/kvfree: Switch to a generic linked list API
From: "Uladzislau Rezki (Sony)" <urezki@...il.com>
This commit improves the readability and maintainability of the
kvfree_rcu() code by switching from an open-coded linked list to
the standard Linux-kernel circular doubly linked list. This patch
does not introduce any functional change.
Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
kernel/rcu/tree.c | 89 +++++++++++++++++++++++------------------------
1 file changed, 43 insertions(+), 46 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 7d222acd85bfd..4088b34ce9610 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2876,13 +2876,13 @@ EXPORT_SYMBOL_GPL(call_rcu);
/**
* struct kvfree_rcu_bulk_data - single block to store kvfree_rcu() pointers
+ * @list: List node. All blocks are linked between each other
* @nr_records: Number of active pointers in the array
- * @next: Next bulk object in the block chain
* @records: Array of the kvfree_rcu() pointers
*/
struct kvfree_rcu_bulk_data {
+ struct list_head list;
unsigned long nr_records;
- struct kvfree_rcu_bulk_data *next;
void *records[];
};
@@ -2898,21 +2898,21 @@ struct kvfree_rcu_bulk_data {
* 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
- * @bkvhead_free: Bulk-List of kvfree_rcu() objects waiting for a grace period
+ * @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 kvfree_rcu_bulk_data *bkvhead_free[FREE_N_CHANNELS];
+ 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
- * @bkvhead: Bulk-List of kvfree_rcu() objects not yet waiting for a grace period
+ * @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
@@ -2936,7 +2936,7 @@ struct kfree_rcu_cpu_work {
*/
struct kfree_rcu_cpu {
struct rcu_head *head;
- struct kvfree_rcu_bulk_data *bkvhead[FREE_N_CHANNELS];
+ struct list_head bulk_head[FREE_N_CHANNELS];
struct kfree_rcu_cpu_work krw_arr[KFREE_N_BATCHES];
raw_spinlock_t lock;
struct delayed_work monitor_work;
@@ -3031,12 +3031,13 @@ drain_page_cache(struct kfree_rcu_cpu *krcp)
/*
* This function is invoked in workqueue context after a grace period.
- * It frees all the objects queued on ->bkvhead_free or ->head_free.
+ * 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 *bkvhead[FREE_N_CHANNELS], *bnext;
+ struct kvfree_rcu_bulk_data *bnode, *n;
+ struct list_head bulk_head[FREE_N_CHANNELS];
struct rcu_head *head, *next;
struct kfree_rcu_cpu *krcp;
struct kfree_rcu_cpu_work *krwp;
@@ -3048,10 +3049,8 @@ static void kfree_rcu_work(struct work_struct *work)
raw_spin_lock_irqsave(&krcp->lock, flags);
// Channels 1 and 2.
- for (i = 0; i < FREE_N_CHANNELS; i++) {
- bkvhead[i] = krwp->bkvhead_free[i];
- krwp->bkvhead_free[i] = NULL;
- }
+ 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;
@@ -3060,36 +3059,33 @@ static void kfree_rcu_work(struct work_struct *work)
// Handle the first two channels.
for (i = 0; i < FREE_N_CHANNELS; i++) {
- for (; bkvhead[i]; bkvhead[i] = bnext) {
- bnext = bkvhead[i]->next;
- debug_rcu_bhead_unqueue(bkvhead[i]);
+ list_for_each_entry_safe(bnode, n, &bulk_head[i], list) {
+ debug_rcu_bhead_unqueue(bnode);
rcu_lock_acquire(&rcu_callback_map);
if (i == 0) { // kmalloc() / kfree().
trace_rcu_invoke_kfree_bulk_callback(
- rcu_state.name, bkvhead[i]->nr_records,
- bkvhead[i]->records);
+ rcu_state.name, bnode->nr_records,
+ bnode->records);
- kfree_bulk(bkvhead[i]->nr_records,
- bkvhead[i]->records);
+ kfree_bulk(bnode->nr_records, bnode->records);
} else { // vmalloc() / vfree().
- for (j = 0; j < bkvhead[i]->nr_records; j++) {
+ for (j = 0; j < bnode->nr_records; j++) {
trace_rcu_invoke_kvfree_callback(
- rcu_state.name,
- bkvhead[i]->records[j], 0);
+ rcu_state.name, bnode->records[j], 0);
- vfree(bkvhead[i]->records[j]);
+ vfree(bnode->records[j]);
}
}
rcu_lock_release(&rcu_callback_map);
raw_spin_lock_irqsave(&krcp->lock, flags);
- if (put_cached_bnode(krcp, bkvhead[i]))
- bkvhead[i] = NULL;
+ if (put_cached_bnode(krcp, bnode))
+ bnode = NULL;
raw_spin_unlock_irqrestore(&krcp->lock, flags);
- if (bkvhead[i])
- free_page((unsigned long) bkvhead[i]);
+ if (bnode)
+ free_page((unsigned long) bnode);
cond_resched_tasks_rcu_qs();
}
@@ -3125,7 +3121,7 @@ need_offload_krc(struct kfree_rcu_cpu *krcp)
int i;
for (i = 0; i < FREE_N_CHANNELS; i++)
- if (krcp->bkvhead[i])
+ if (!list_empty(&krcp->bulk_head[i]))
return true;
return !!krcp->head;
@@ -3162,21 +3158,20 @@ static void kfree_rcu_monitor(struct work_struct *work)
for (i = 0; i < KFREE_N_BATCHES; i++) {
struct kfree_rcu_cpu_work *krwp = &(krcp->krw_arr[i]);
- // Try to detach bkvhead or head and attach it over any
+ // Try to detach bulk_head or head and attach it over any
// available corresponding free channel. It can be that
// a previous RCU batch is in progress, it means that
// immediately to queue another one is not possible so
// in that case the monitor work is rearmed.
- if ((krcp->bkvhead[0] && !krwp->bkvhead_free[0]) ||
- (krcp->bkvhead[1] && !krwp->bkvhead_free[1]) ||
+ if ((!list_empty(&krcp->bulk_head[0]) && list_empty(&krwp->bulk_head_free[0])) ||
+ (!list_empty(&krcp->bulk_head[1]) && list_empty(&krwp->bulk_head_free[1])) ||
(krcp->head && !krwp->head_free)) {
+
// 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 (!krwp->bkvhead_free[j]) {
- krwp->bkvhead_free[j] = krcp->bkvhead[j];
- krcp->bkvhead[j] = NULL;
- }
+ if (list_empty(&krwp->bulk_head_free[j]))
+ list_replace_init(&krcp->bulk_head[j], &krwp->bulk_head_free[j]);
}
// Channel 3 corresponds to both SLAB and vmalloc
@@ -3288,10 +3283,11 @@ add_ptr_to_bulk_krc_lock(struct kfree_rcu_cpu **krcp,
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 (!(*krcp)->bkvhead[idx] ||
- (*krcp)->bkvhead[idx]->nr_records == KVFREE_BULK_MAX_ENTR) {
+ if (!bnode || bnode->nr_records == KVFREE_BULK_MAX_ENTR) {
bnode = get_cached_bnode(*krcp);
if (!bnode && can_alloc) {
krc_this_cpu_unlock(*krcp, *flags);
@@ -3315,18 +3311,13 @@ add_ptr_to_bulk_krc_lock(struct kfree_rcu_cpu **krcp,
if (!bnode)
return false;
- /* Initialize the new block. */
+ // Initialize the new block and attach it.
bnode->nr_records = 0;
- bnode->next = (*krcp)->bkvhead[idx];
-
- /* Attach it to the head. */
- (*krcp)->bkvhead[idx] = bnode;
+ list_add(&bnode->list, &(*krcp)->bulk_head[idx]);
}
/* Finally insert. */
- (*krcp)->bkvhead[idx]->records
- [(*krcp)->bkvhead[idx]->nr_records++] = ptr;
-
+ bnode->records[bnode->nr_records++] = ptr;
return true;
}
@@ -4761,7 +4752,7 @@ struct workqueue_struct *rcu_gp_wq;
static void __init kfree_rcu_batch_init(void)
{
int cpu;
- int i;
+ int i, j;
/* Clamp it to [0:100] seconds interval. */
if (rcu_delay_page_cache_fill_msec < 0 ||
@@ -4781,8 +4772,14 @@ static void __init kfree_rcu_batch_init(void)
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;
--
2.31.1.189.g2e36527f23
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