From patchwork Thu Jan 5 00:24:42 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Paul E. McKenney" X-Patchwork-Id: 13089253 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E6BEBC54EBE for ; Thu, 5 Jan 2023 00:27:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235724AbjAEA0g (ORCPT ); Wed, 4 Jan 2023 19:26:36 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33316 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235494AbjAEA0G (ORCPT ); Wed, 4 Jan 2023 19:26:06 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4F3654FD78; Wed, 4 Jan 2023 16:24:52 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id DC16761880; Thu, 5 Jan 2023 00:24:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3330EC433D2; Thu, 5 Jan 2023 00:24:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1672878290; bh=9q3RXJaEMI0bXFO/vylOhYFyrOVZOPbjbOVjXgIBpGc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=OFXK80sEV5h+vkOB8PnwWECzrbUYp/b297NgAZahEHq44//vzGeqCFZtKKqfathpL qmXHwFA/fOFCI2EzaUykt6N6qrfDAEDh7ntVvMBEW3laHX2zk+cSpEzkrffK+yPywC gnGwKMAmwG5HeM5QA4YeK/DuCLWOMvgg5eZR2esF0Jmj8IJrAnxBVB8ys+mm7HCfzL 3wm0NOhK68AWOJncmc/oEYVMykLfcH1G2oQhufRoGw42KFvRQI4J9+1OvaVYOk6oYb ZmJkeg6GA54gLhya4oyXN7EEDpp2+MBdfMocrTFTTxhC+UoU8PV3fQn1gMJ01BEZH0 TD+2y0KCVSTTA== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id E27975C086D; Wed, 4 Jan 2023 16:24:49 -0800 (PST) From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Uladzislau Rezki (Sony)" , "Paul E . McKenney" Subject: [PATCH rcu 2/8] rcu/kvfree: Switch to a generic linked list API Date: Wed, 4 Jan 2023 16:24:42 -0800 Message-Id: <20230105002448.1768892-2-paulmck@kernel.org> X-Mailer: git-send-email 2.31.1.189.g2e36527f23 In-Reply-To: <20230105002441.GA1768817@paulmck-ThinkPad-P17-Gen-1> References: <20230105002441.GA1768817@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org From: "Uladzislau Rezki (Sony)" 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) Signed-off-by: Paul E. McKenney --- 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;