From mboxrd@z Thu Jan 1 00:00:00 1970 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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 0C0B1109C05B for ; Wed, 25 Mar 2026 19:30:46 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 162666B0005; Wed, 25 Mar 2026 15:30:46 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 113536B0089; Wed, 25 Mar 2026 15:30:46 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F1D1C6B008A; Wed, 25 Mar 2026 15:30:45 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id DD8DF6B0005 for ; Wed, 25 Mar 2026 15:30:45 -0400 (EDT) Received: from smtpin24.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 8497713BAE5 for ; Wed, 25 Mar 2026 19:30:45 +0000 (UTC) X-FDA: 84585577650.24.EFE2D73 Received: from mx0b-00364e01.pphosted.com (mx0b-00364e01.pphosted.com [148.163.139.74]) by imf05.hostedemail.com (Postfix) with ESMTP id 9370910001B for ; Wed, 25 Mar 2026 19:30:42 +0000 (UTC) Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=columbia.edu header.s=pps01 header.b=W1TdmHAg; dmarc=pass (policy=none) header.from=columbia.edu; spf=pass (imf05.hostedemail.com: domain of tz2294@columbia.edu designates 148.163.139.74 as permitted sender) smtp.mailfrom=tz2294@columbia.edu ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1774467043; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=hCcp+9kU8miIdEe20LAeTwI4JkSmuzG2q+hEwpZi3Vg=; b=6wvi8cPAuU4OnNwfOSPlGUT3WjxMJbgFfPXO0TZdCBHjcJ1gjfnbmaoenW/5gGwt3K3RSr 1OIVvFIdZSwuD9ENLEXKpCcMuuXPfE/dpi3NcJccl6RwR98q4pn45FlypqZPlBeU1M2rIK ax+HcI7g1k1J8UC3+cPDOR/RjpKRCU8= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1774467043; a=rsa-sha256; cv=none; b=Jx44DBu/Gbk0zK85ud935gpZQ5qd6xIIZE3SEm4Sd1/JPFE2SCHH9NphLKXoCtP+aKKmmV PZLTfKSFhL3x4/oBstwFU6F+1qMb1bEMgPfdcViasRhM/fx0DS83sPcemew8oZ+3iWhHQa d9E7a1G9dYU2GUMNrEw9lNDznXoTS+A= ARC-Authentication-Results: i=1; imf05.hostedemail.com; dkim=pass header.d=columbia.edu header.s=pps01 header.b=W1TdmHAg; dmarc=pass (policy=none) header.from=columbia.edu; spf=pass (imf05.hostedemail.com: domain of tz2294@columbia.edu designates 148.163.139.74 as permitted sender) smtp.mailfrom=tz2294@columbia.edu Received: from pps.filterd (m0499198.ppops.net [127.0.0.1]) by mx0b-00364e01.pphosted.com (8.18.1.11/8.18.1.11) with ESMTP id 62PJSfZ6937217 for ; Wed, 25 Mar 2026 15:30:41 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=columbia.edu; h= cc:content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to; s=pps01; bh=hCcp +9kU8miIdEe20LAeTwI4JkSmuzG2q+hEwpZi3Vg=; b=W1TdmHAgxdl1P3Jt415K mDMuXC1UZ38fH1pCdmPKkiGohuKsIY1BtpAKPFqF+lIJQhgQdYdxNmq0tBln+Sxi fPo2lZn/xTrr7aF03NAH5D7o5dhQ7+BnqTNuev7JxaZBdfr7G70Mgv6aC67YHW6I jiNkss/3Gc3BnDCLsPz4kOq4H0P3arP/tm4ywo+FaBzzT+wYpZi3+xYTVHK+aRCm JPQkw9rJlEHkxRJkqF13de3U36pc5j9+MK4SNkjL0L6/hXAbd+/klpJMM5KCVdqx 7xFJfUckpL/QeBuUOmtLU/DH2jbtDRoN06GcP8GdoC+DVlnJMZbwsJFM28SMa1+f IA== Received: from mail-qt1-f200.google.com (mail-qt1-f200.google.com [209.85.160.200]) by mx0b-00364e01.pphosted.com (PPS) with ESMTPS id 4d4h98ayhj-1 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NOT) for ; Wed, 25 Mar 2026 15:30:41 -0400 (EDT) Received: by mail-qt1-f200.google.com with SMTP id d75a77b69052e-509044f54aaso8550261cf.1 for ; Wed, 25 Mar 2026 12:30:41 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1774467041; x=1775071841; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :mime-version:subject:date:from:x-gm-gg:x-gm-message-state:from:to :cc:subject:date:message-id:reply-to; bh=hCcp+9kU8miIdEe20LAeTwI4JkSmuzG2q+hEwpZi3Vg=; b=bNTzUyu0JVGsskbK0C8/q/AjHmaFHto/sW8Y4y1BEgpc6qLythxJ1AtvlMHP3XM4EK Tsmmj2COtIZBtismo7m5jC3+twQdu9GcIqK1PO/6cXMU/PfhGEv1s3vTqa3wc13DHt+p hXabSuR6eYviv+hJG3ylPFd77En8VxJT9MXyI6inhmD0x5VesrV+aFCbtEYQXH60JqZK rmmzclXZPOIJ3QdiDK+MjNafQI9+aiGNAtqlzTqmcKQ48zdieg6gin8YXgIGyOp6RiFB EdaxvI0uxNPuTaVS95K4/sbjmX+eeY65CYaCPCZ7UMRY1AUYi/fSWvWIGIul6319NEsD LzKg== X-Forwarded-Encrypted: i=1; AJvYcCWHNlrqVKvJtypiCLqAMuXy/evGF+HSWgiZ1eFZ2gCMbtgEFHTYahGV0PqqwVwz+bpk4xMJ4fjFjA==@kvack.org X-Gm-Message-State: AOJu0YzFJZA4NCpbcVUe68CqsNFuc0vLF/BIAGQrZzEqc9q+vFrrbddH L2DLpETuvnUfX7hQcEwyhCcKjbMl+nEDkCN6rGg7UU8091hRm4SqKGvOPxUPBviM865JyZgvWdY tJtlB0DiuiZhe1HiNAtSwqD5dzVBSi+eZbVBTVQQ9kxKiBkKw X-Gm-Gg: ATEYQzwS6AfFiWSDCZR/pJTPCOGFfVkNi6z5oET7Efk9dxezg9rUftsBCcdJL+QVlzh dJL5rasEXDlHWC6yOXEugygcNni5i435zF0ojBAgsEPmCKUrxcF5ZWEeDLVTzo4sPPUTxlbNcHy R6SZxrEH5Nj1kgLPZkCZpZnaWWKWTMaVum4k6cG4bOfp1GAqNIGJOI/XwFqgBm8140VBn5yHrKW aSvwLoHX5NM0hTq+peemF3WxyACFuIoumE/Cbk+EPKi8m1Ymj4gpJ4Y7vtN8gEmqPv9PneVymXc uxUlsZfe4NvVzBN07bKCv9iGibiA+m4iFHn+0r++owL4WBzHXZJvXsSi8vTty2EFIgzdXXEpG0N Vk/JsfwSHXZoK9yYbHv+odybymBrj39ywb+rwaA== X-Received: by 2002:a05:622a:8356:b0:50b:4f75:c925 with SMTP id d75a77b69052e-50b80d34c05mr57540531cf.24.1774467040642; Wed, 25 Mar 2026 12:30:40 -0700 (PDT) X-Received: by 2002:a05:622a:8356:b0:50b:4f75:c925 with SMTP id d75a77b69052e-50b80d34c05mr57539811cf.24.1774467040081; Wed, 25 Mar 2026 12:30:40 -0700 (PDT) Received: from [127.0.1.1] ([129.236.226.199]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-50b9234e3a3sm5534221cf.19.2026.03.25.12.30.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Mar 2026 12:30:39 -0700 (PDT) From: Tal Zussman Date: Wed, 25 Mar 2026 14:43:00 -0400 Subject: [PATCH RFC v4 1/3] block: add BIO_COMPLETE_IN_TASK for task-context completion MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260325-blk-dontcache-v4-1-c4b56db43f64@columbia.edu> References: <20260325-blk-dontcache-v4-0-c4b56db43f64@columbia.edu> In-Reply-To: <20260325-blk-dontcache-v4-0-c4b56db43f64@columbia.edu> To: Jens Axboe , "Matthew Wilcox (Oracle)" , Christian Brauner , "Darrick J. Wong" , Carlos Maiolino , Alexander Viro , Jan Kara Cc: Christoph Hellwig , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Tal Zussman X-Mailer: b4 0.14.3-dev-d7477 X-Developer-Signature: v=1; a=ed25519-sha256; t=1774464193; l=4684; i=tz2294@columbia.edu; s=20250528; h=from:subject:message-id; bh=/KDtCfPcROGMHktI+sYIoy1sJXxmr+t5YwMIoFyxNlk=; b=yUgCWQ4ZcEeNTx5iojZlwuLJ75/zRFsFdFta96TVVGE0YTzeH6B4RKXjHrIwyFGw3hTK3rhgt gf2gbHu8FZ6CWKrHyJPeTOd+yuu9FyglPNZhfk8bDp7xeu7U5SJLlSh X-Developer-Key: i=tz2294@columbia.edu; a=ed25519; pk=BIj5KdACscEOyAC0oIkeZqLB3L94fzBnDccEooxeM5Y= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzI1MDE0MiBTYWx0ZWRfX8G1FnaZfuLpZ gS/tgsxftQ3fEz7RT6brUXQ517wIeCbDQdR47hbiHoztkotH2XtSovh9HuwqnfsGpPvrbZUruZx Ja+TITFHZnht1NlyhkESeKuDvOn9Y22sLBEfOiMZTVUOqjR9koIBM86WGLKodgoTth6qrZUw0bR zItUPDbUKFvRs9JDblr/g6Pmir5XVuo46sfHDXcTVgFiPSyZQLnhY4icQLK/EAa7o5ofFHD65K3 i4xoY+sdeM8pGW0azhf1FPkg+TWahX9zST1aDvM70QfS9K+a9tIe/IeIPaRfr9rZTxSyMQELybF cFeVRAbtodhPPwFu6J4zBkeLGyRmgdZHdRdxIWaMkcArf3v3WOnkOh1sbzxuGwdUJF+238myhV7 GQ2rmzp0praG99Z4pXvAuCWGoY7w2dCuUJvnDBN9DIijIUJAxCw4E8kSZnruH6pm/SaGoZX//iD tWmJzbTiu5NsPONrQuA== X-Proofpoint-ORIG-GUID: GrB5QuzMAfKfIxHoOksLWb3SvaG-NeaR X-Proofpoint-GUID: GrB5QuzMAfKfIxHoOksLWb3SvaG-NeaR X-Authority-Analysis: v=2.4 cv=Ht572kTS c=1 sm=1 tr=0 ts=69c437e1 cx=c_pps a=JbAStetqSzwMeJznSMzCyw==:117 a=QOUmeeuX5y9IvSxXHa6D2A==:17 a=IkcTkHD0fZMA:10 a=Yq5XynenixoA:10 a=x7bEGLp0ZPQA:10 a=VkNPw1HP01LnGYTKEx00:22 a=Da8U98TiO7q1upZEImrf:22 a=BpGzv1V74M3SfeTrGa8v:22 a=JfrnYn6hAAAA:8 a=QQSmTEQkt36Rj1JXOw4A:9 a=QEXdDO2ut3YA:10 a=uxP6HrT_eTzRwkO_Te1X:22 a=1CNFftbPRP8L7MoqJWF3:22 X-Proofpoint-Virus-Version: vendor=nai engine=6800 definitions=11740 signatures=596818 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 impostorscore=10 lowpriorityscore=10 bulkscore=10 clxscore=1015 priorityscore=1501 spamscore=0 adultscore=0 phishscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2603250142 X-Rspamd-Queue-Id: 9370910001B X-Stat-Signature: g1uwhh9odcr85ckmpomwhgxrq31ke3fg X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1774467042-640100 X-HE-Meta: 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 wFe+StUh 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Some bio completion handlers need to run in task context but bio_endio() can be called from IRQ context (e.g. buffer_head writeback). Add a BIO_COMPLETE_IN_TASK flag that bio submitters can set to request task-context completion of their bi_end_io callback. When bio_endio() sees this flag and is running in non-task context, it queues the bio to a per-cpu list and schedules a work item to call bi_end_io() from task context. A CPU hotplug dead callback drains any remaining bios from the departing CPU's batch. This will be used to enable RWF_DONTCACHE for block devices, and could be used for other subsystems like fscrypt that need task-context bio completion. Suggested-by: Matthew Wilcox Signed-off-by: Tal Zussman --- block/bio.c | 84 ++++++++++++++++++++++++++++++++++++++++++++++- include/linux/blk_types.h | 1 + 2 files changed, 84 insertions(+), 1 deletion(-) diff --git a/block/bio.c b/block/bio.c index 8203bb7455a9..69ee0d93041f 100644 --- a/block/bio.c +++ b/block/bio.c @@ -18,6 +18,7 @@ #include #include #include +#include #include #include "blk.h" @@ -1714,6 +1715,60 @@ void bio_check_pages_dirty(struct bio *bio) } EXPORT_SYMBOL_GPL(bio_check_pages_dirty); +struct bio_complete_batch { + local_lock_t lock; + struct bio_list list; + struct work_struct work; +}; + +static DEFINE_PER_CPU(struct bio_complete_batch, bio_complete_batch) = { + .lock = INIT_LOCAL_LOCK(lock), +}; + +static void bio_complete_work_fn(struct work_struct *w) +{ + struct bio_complete_batch *batch; + struct bio_list list; + +again: + local_lock_irq(&bio_complete_batch.lock); + batch = this_cpu_ptr(&bio_complete_batch); + list = batch->list; + bio_list_init(&batch->list); + local_unlock_irq(&bio_complete_batch.lock); + + while (!bio_list_empty(&list)) { + struct bio *bio = bio_list_pop(&list); + bio->bi_end_io(bio); + } + + local_lock_irq(&bio_complete_batch.lock); + batch = this_cpu_ptr(&bio_complete_batch); + if (!bio_list_empty(&batch->list)) { + local_unlock_irq(&bio_complete_batch.lock); + + if (!need_resched()) + goto again; + + schedule_work_on(smp_processor_id(), &batch->work); + return; + } + local_unlock_irq(&bio_complete_batch.lock); +} + +static void bio_queue_completion(struct bio *bio) +{ + struct bio_complete_batch *batch; + unsigned long flags; + + local_lock_irqsave(&bio_complete_batch.lock, flags); + batch = this_cpu_ptr(&bio_complete_batch); + bio_list_add(&batch->list, bio); + local_unlock_irqrestore(&bio_complete_batch.lock, flags); + + schedule_work_on(smp_processor_id(), &batch->work); +} + static inline bool bio_remaining_done(struct bio *bio) { /* @@ -1788,7 +1843,9 @@ void bio_endio(struct bio *bio) } #endif - if (bio->bi_end_io) + if (!in_task() && bio_flagged(bio, BIO_COMPLETE_IN_TASK)) + bio_queue_completion(bio); + else if (bio->bi_end_io) bio->bi_end_io(bio); } EXPORT_SYMBOL(bio_endio); @@ -1974,6 +2031,21 @@ int bioset_init(struct bio_set *bs, } EXPORT_SYMBOL(bioset_init); +/* + * Drain a dead CPU's deferred bio completions. The CPU is dead so no locking + * is needed -- no new bios will be queued to it. + */ +static int bio_complete_batch_cpu_dead(unsigned int cpu) +{ + struct bio_complete_batch *batch = per_cpu_ptr(&bio_complete_batch, cpu); + struct bio *bio; + + while ((bio = bio_list_pop(&batch->list))) + bio->bi_end_io(bio); + + return 0; +} + static int __init init_bio(void) { int i; @@ -1988,6 +2060,16 @@ static int __init init_bio(void) SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); } + for_each_possible_cpu(i) { + struct bio_complete_batch *batch = + per_cpu_ptr(&bio_complete_batch, i); + + bio_list_init(&batch->list); + INIT_WORK(&batch->work, bio_complete_work_fn); + } + + cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "block/bio:complete:dead", + NULL, bio_complete_batch_cpu_dead); cpuhp_setup_state_multi(CPUHP_BIO_DEAD, "block/bio:dead", NULL, bio_cpu_dead); diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h index 8808ee76e73c..d49d97a050d0 100644 --- a/include/linux/blk_types.h +++ b/include/linux/blk_types.h @@ -322,6 +322,7 @@ enum { BIO_REMAPPED, BIO_ZONE_WRITE_PLUGGING, /* bio handled through zone write plugging */ BIO_EMULATES_ZONE_APPEND, /* bio emulates a zone append operation */ + BIO_COMPLETE_IN_TASK, /* complete bi_end_io() in task context */ BIO_FLAG_LAST }; -- 2.39.5