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rcu/kvfree: Switch to a generic linked list API
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@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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@ -2876,13 +2876,13 @@ EXPORT_SYMBOL_GPL(call_rcu);
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/**
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* struct kvfree_rcu_bulk_data - single block to store kvfree_rcu() pointers
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* @list: List node. All blocks are linked between each other
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* @nr_records: Number of active pointers in the array
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* @next: Next bulk object in the block chain
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* @records: Array of the kvfree_rcu() pointers
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*/
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struct kvfree_rcu_bulk_data {
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struct list_head list;
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unsigned long nr_records;
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struct kvfree_rcu_bulk_data *next;
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void *records[];
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};
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@ -2898,21 +2898,21 @@ struct kvfree_rcu_bulk_data {
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* struct kfree_rcu_cpu_work - single batch of kfree_rcu() requests
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* @rcu_work: Let queue_rcu_work() invoke workqueue handler after grace period
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* @head_free: List of kfree_rcu() objects waiting for a grace period
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* @bkvhead_free: Bulk-List of kvfree_rcu() objects waiting for a grace period
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* @bulk_head_free: Bulk-List of kvfree_rcu() objects waiting for a grace period
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* @krcp: Pointer to @kfree_rcu_cpu structure
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*/
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struct kfree_rcu_cpu_work {
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struct rcu_work rcu_work;
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struct rcu_head *head_free;
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struct kvfree_rcu_bulk_data *bkvhead_free[FREE_N_CHANNELS];
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struct list_head bulk_head_free[FREE_N_CHANNELS];
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struct kfree_rcu_cpu *krcp;
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};
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/**
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* struct kfree_rcu_cpu - batch up kfree_rcu() requests for RCU grace period
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* @head: List of kfree_rcu() objects not yet waiting for a grace period
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* @bkvhead: Bulk-List of kvfree_rcu() objects not yet waiting for a grace period
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* @bulk_head: Bulk-List of kvfree_rcu() objects not yet waiting for a grace period
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* @krw_arr: Array of batches of kfree_rcu() objects waiting for a grace period
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* @lock: Synchronize access to this structure
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* @monitor_work: Promote @head to @head_free after KFREE_DRAIN_JIFFIES
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@ -2936,7 +2936,7 @@ struct kfree_rcu_cpu_work {
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*/
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struct kfree_rcu_cpu {
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struct rcu_head *head;
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struct kvfree_rcu_bulk_data *bkvhead[FREE_N_CHANNELS];
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struct list_head bulk_head[FREE_N_CHANNELS];
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struct kfree_rcu_cpu_work krw_arr[KFREE_N_BATCHES];
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raw_spinlock_t lock;
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struct delayed_work monitor_work;
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@ -3031,12 +3031,13 @@ drain_page_cache(struct kfree_rcu_cpu *krcp)
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/*
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* This function is invoked in workqueue context after a grace period.
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* It frees all the objects queued on ->bkvhead_free or ->head_free.
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* It frees all the objects queued on ->bulk_head_free or ->head_free.
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*/
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static void kfree_rcu_work(struct work_struct *work)
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{
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unsigned long flags;
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struct kvfree_rcu_bulk_data *bkvhead[FREE_N_CHANNELS], *bnext;
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struct kvfree_rcu_bulk_data *bnode, *n;
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struct list_head bulk_head[FREE_N_CHANNELS];
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struct rcu_head *head, *next;
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struct kfree_rcu_cpu *krcp;
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struct kfree_rcu_cpu_work *krwp;
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@ -3048,10 +3049,8 @@ static void kfree_rcu_work(struct work_struct *work)
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raw_spin_lock_irqsave(&krcp->lock, flags);
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// Channels 1 and 2.
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for (i = 0; i < FREE_N_CHANNELS; i++) {
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bkvhead[i] = krwp->bkvhead_free[i];
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krwp->bkvhead_free[i] = NULL;
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}
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for (i = 0; i < FREE_N_CHANNELS; i++)
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list_replace_init(&krwp->bulk_head_free[i], &bulk_head[i]);
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// Channel 3.
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head = krwp->head_free;
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@ -3060,36 +3059,33 @@ static void kfree_rcu_work(struct work_struct *work)
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// Handle the first two channels.
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for (i = 0; i < FREE_N_CHANNELS; i++) {
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for (; bkvhead[i]; bkvhead[i] = bnext) {
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bnext = bkvhead[i]->next;
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debug_rcu_bhead_unqueue(bkvhead[i]);
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list_for_each_entry_safe(bnode, n, &bulk_head[i], list) {
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debug_rcu_bhead_unqueue(bnode);
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rcu_lock_acquire(&rcu_callback_map);
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if (i == 0) { // kmalloc() / kfree().
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trace_rcu_invoke_kfree_bulk_callback(
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rcu_state.name, bkvhead[i]->nr_records,
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bkvhead[i]->records);
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rcu_state.name, bnode->nr_records,
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bnode->records);
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kfree_bulk(bkvhead[i]->nr_records,
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bkvhead[i]->records);
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kfree_bulk(bnode->nr_records, bnode->records);
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} else { // vmalloc() / vfree().
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for (j = 0; j < bkvhead[i]->nr_records; j++) {
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for (j = 0; j < bnode->nr_records; j++) {
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trace_rcu_invoke_kvfree_callback(
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rcu_state.name,
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bkvhead[i]->records[j], 0);
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rcu_state.name, bnode->records[j], 0);
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vfree(bkvhead[i]->records[j]);
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vfree(bnode->records[j]);
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}
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}
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rcu_lock_release(&rcu_callback_map);
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raw_spin_lock_irqsave(&krcp->lock, flags);
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if (put_cached_bnode(krcp, bkvhead[i]))
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bkvhead[i] = NULL;
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if (put_cached_bnode(krcp, bnode))
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bnode = NULL;
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raw_spin_unlock_irqrestore(&krcp->lock, flags);
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if (bkvhead[i])
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free_page((unsigned long) bkvhead[i]);
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if (bnode)
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free_page((unsigned long) bnode);
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cond_resched_tasks_rcu_qs();
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}
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@ -3125,7 +3121,7 @@ need_offload_krc(struct kfree_rcu_cpu *krcp)
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int i;
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for (i = 0; i < FREE_N_CHANNELS; i++)
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if (krcp->bkvhead[i])
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if (!list_empty(&krcp->bulk_head[i]))
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return true;
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return !!krcp->head;
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@ -3162,21 +3158,20 @@ static void kfree_rcu_monitor(struct work_struct *work)
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for (i = 0; i < KFREE_N_BATCHES; i++) {
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struct kfree_rcu_cpu_work *krwp = &(krcp->krw_arr[i]);
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// Try to detach bkvhead or head and attach it over any
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// Try to detach bulk_head or head and attach it over any
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// available corresponding free channel. It can be that
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// a previous RCU batch is in progress, it means that
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// immediately to queue another one is not possible so
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// in that case the monitor work is rearmed.
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if ((krcp->bkvhead[0] && !krwp->bkvhead_free[0]) ||
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(krcp->bkvhead[1] && !krwp->bkvhead_free[1]) ||
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if ((!list_empty(&krcp->bulk_head[0]) && list_empty(&krwp->bulk_head_free[0])) ||
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(!list_empty(&krcp->bulk_head[1]) && list_empty(&krwp->bulk_head_free[1])) ||
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(krcp->head && !krwp->head_free)) {
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// Channel 1 corresponds to the SLAB-pointer bulk path.
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// Channel 2 corresponds to vmalloc-pointer bulk path.
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for (j = 0; j < FREE_N_CHANNELS; j++) {
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if (!krwp->bkvhead_free[j]) {
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krwp->bkvhead_free[j] = krcp->bkvhead[j];
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krcp->bkvhead[j] = NULL;
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}
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if (list_empty(&krwp->bulk_head_free[j]))
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list_replace_init(&krcp->bulk_head[j], &krwp->bulk_head_free[j]);
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}
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// Channel 3 corresponds to both SLAB and vmalloc
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@ -3288,10 +3283,11 @@ add_ptr_to_bulk_krc_lock(struct kfree_rcu_cpu **krcp,
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return false;
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idx = !!is_vmalloc_addr(ptr);
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bnode = list_first_entry_or_null(&(*krcp)->bulk_head[idx],
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struct kvfree_rcu_bulk_data, list);
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/* Check if a new block is required. */
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if (!(*krcp)->bkvhead[idx] ||
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(*krcp)->bkvhead[idx]->nr_records == KVFREE_BULK_MAX_ENTR) {
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if (!bnode || bnode->nr_records == KVFREE_BULK_MAX_ENTR) {
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bnode = get_cached_bnode(*krcp);
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if (!bnode && can_alloc) {
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krc_this_cpu_unlock(*krcp, *flags);
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@ -3315,18 +3311,13 @@ add_ptr_to_bulk_krc_lock(struct kfree_rcu_cpu **krcp,
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if (!bnode)
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return false;
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/* Initialize the new block. */
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// Initialize the new block and attach it.
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bnode->nr_records = 0;
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bnode->next = (*krcp)->bkvhead[idx];
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/* Attach it to the head. */
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(*krcp)->bkvhead[idx] = bnode;
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list_add(&bnode->list, &(*krcp)->bulk_head[idx]);
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}
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/* Finally insert. */
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(*krcp)->bkvhead[idx]->records
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[(*krcp)->bkvhead[idx]->nr_records++] = ptr;
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bnode->records[bnode->nr_records++] = ptr;
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return true;
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}
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@ -4761,7 +4752,7 @@ struct workqueue_struct *rcu_gp_wq;
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static void __init kfree_rcu_batch_init(void)
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{
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int cpu;
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int i;
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int i, j;
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/* Clamp it to [0:100] seconds interval. */
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if (rcu_delay_page_cache_fill_msec < 0 ||
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@ -4781,8 +4772,14 @@ static void __init kfree_rcu_batch_init(void)
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for (i = 0; i < KFREE_N_BATCHES; i++) {
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INIT_RCU_WORK(&krcp->krw_arr[i].rcu_work, kfree_rcu_work);
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krcp->krw_arr[i].krcp = krcp;
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for (j = 0; j < FREE_N_CHANNELS; j++)
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INIT_LIST_HEAD(&krcp->krw_arr[i].bulk_head_free[j]);
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}
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for (i = 0; i < FREE_N_CHANNELS; i++)
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INIT_LIST_HEAD(&krcp->bulk_head[i]);
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INIT_DELAYED_WORK(&krcp->monitor_work, kfree_rcu_monitor);
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INIT_DELAYED_WORK(&krcp->page_cache_work, fill_page_cache_func);
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krcp->initialized = true;
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