From nobody Fri Apr 3 01:29:35 2026 Received: from mx0b-00364e01.pphosted.com (mx0b-00364e01.pphosted.com [148.163.139.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0A5713EBF26 for ; Wed, 25 Mar 2026 19:44:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=148.163.139.74 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774467856; cv=none; b=R0tDDv+pPwLZfSGcYkYlIPcFONh0MjkByRLKZik0pb19dP4eExXKj0/E1zmr9drLLElOOem7XJgEybmjvCd63WA3Yefr0F+SXvPomdRanK2ProMhQ5IKnFPNKRa+IpDLlpkYoz8xeIPwmwiyg7rKtcqoVV+4kvVaUQSJQQ7xKt8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774467856; c=relaxed/simple; bh=/KDtCfPcROGMHktI+sYIoy1sJXxmr+t5YwMIoFyxNlk=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=RCjOLjK34JmmLOOXtLwx+XwtJtZEg3qSUi2ktVl9VaHIBm4uLZh2hDMjfs2nX20XC0sO+D93vlYtvDnQuBkpSl4BMjFzLzBHPymCCkGmCGkm8QIvqy2T1GvYIZZfyFLEqEo49tQg0z8KqQ6S4v2o2RG6+uZ2EmKhSQhUSu8tfeM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=columbia.edu; spf=pass smtp.mailfrom=columbia.edu; dkim=pass (2048-bit key) header.d=columbia.edu header.i=@columbia.edu header.b=W1TdmHAg; arc=none smtp.client-ip=148.163.139.74 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=columbia.edu Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=columbia.edu Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=columbia.edu header.i=@columbia.edu header.b="W1TdmHAg" Received: from pps.filterd (m0167074.ppops.net [127.0.0.1]) by mx0b-00364e01.pphosted.com (8.18.1.11/8.18.1.11) with ESMTP id 62PJSZ4d3111413 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 4d474u5u4s-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-50911c94db1so7351611cf.0 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=n69k908QuTklOXBn/GsMoUdZwYbzzyzWxIeYKT7f7QWMWwf1P0RlbU5ORDYwXMOoH9 E0FNvqLTupEyON4SYEobeS7bSlX3KVa02hljDRNQ8z6dTcw8NCDBv+OzrSsrnh3FxFIn o40f/tKFeB1/Ed8EXUe6dDwWOOWqpqKD7ijNxPSnZKtCyuV/YbTcNsGhDTGkPaURL6sP 9ajPa0DrJffwZSqZan0XsYobcV9yABnKP9yIZuM6aF1xq1KDTk5gFHSfpjtJkw8x3m0N XpTADOrGjPTe9CHNycFlmiJzH76UJpQqx/Be6LbAEU0K63IeYiBaAvbmtpUKE/7h7Djy oPmw== X-Forwarded-Encrypted: i=1; AJvYcCUNnOonSQDiC1t4RUqvoRRdAGajrFr2m2hWTDCmJy9MZiI08yoxBfa92kpOInZhzTuFmhjE6Um2n/OcyaA=@vger.kernel.org X-Gm-Message-State: AOJu0YxjWcbrKyaxic8cm/riyZNcmLdFVLsImRwyrwTWbbprg6v7XSYL K00Mf1zu886iSqe7XTkwjuLQklF1ktRd+iFAfUQoJM0Sugf/TKqHcG0QSWA5s/S1/Oyf57ror+I WRppqYxOeDI3En4PrfBkAHK97ARfRAA8LajsTZl8EOOtPnQMz0BaidmaELH5oyw== X-Gm-Gg: ATEYQzwq7WPfU7HjZiVefZ+sZoeT5xuY5iWjOXHk6GfXJipFLpjumZV2RNHDXWu2hV0 N1MYC56z2q8MO2y9erC3/QI1QhG5Vbto/h8n/6P/kUrvYzNFzmP8TgSDFdx9Kv93btGjcIc6XNY jLDmfRjRNXjAPRPewyywNcLHPmGPuzX5JNOHGAVWeJl0UUJN7Zf0M1QRy2hwQwHka8pNjT2I1aC 6mkqsBIGsG6Q4iGET1kk6ytrG+Eu1IVQw/9Je7WMBIfHhXRbfNuOzh/0ENMr6C199Djs24drvtn HEWvb1k1m8zY3pjwKSiYJr4TENQRwBiF+Zoz18zW/A75DD52TA6ioF2HrrEur+WhfMk688IMdfC dUCEwIZtobKWvp5pEs431pJvosX7VGvLtNDk0uw== X-Received: by 2002:a05:622a:8356:b0:50b:4f75:c925 with SMTP id d75a77b69052e-50b80d34c05mr57540471cf.24.1774467040640; 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 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable 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: AW1haW4tMjYwMzI1MDE0MiBTYWx0ZWRfX65WlW+UiJx56 0SKoJnx1sULQ7fI1dy9nDpKG/N5UvQULb0TSWNbpRMPq3Mdwqe7AxFFNhGzbDN29UyUSmx4adFm 5Zdwz7N5RSgh/846AIFoMugbeCXAFO6e3OaiHI6UzN21z3VYxMmBOiFpfHBPN5FaOuHH7LYLyBV v0JHhZMsac9pyrXJT8AGKWG+GkUnHiEqOOExxk7Uw3FatJ3VnU0khWh8hFDc+4otKnsKWhQxEYE DyeqToj/HnUd53ybYVH0u4q4EugmkZZk6PXGFRo7Be1im+iLWTq3CMbOETN/0HgXyVS/p4tnYtU eHrkG2LCZXHrGsz+I1EhqFTKcHCsONuGf+LGWzeD+JmiASx5pvfvDmU0J86vmDR9nAmTtKutR9R g5vCic68smn/I8/M9Vn0atKsG/YP+qGQv1xL8Z9h03fdJPNR4lZ0qEXC6eCYJSj0KYCF7dw1+A5 mKxwAf0GvKl3O06L3Tw== X-Proofpoint-GUID: PeJIs6rHPYxV7D03TWrzIpt-pQYWFpZF X-Authority-Analysis: v=2.4 cv=ANMIVkx+ 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=azVShVRs0zEubeQ0wG0L:22 a=JfrnYn6hAAAA:8 a=QQSmTEQkt36Rj1JXOw4A:9 a=QEXdDO2ut3YA:10 a=uxP6HrT_eTzRwkO_Te1X:22 a=1CNFftbPRP8L7MoqJWF3:22 X-Proofpoint-ORIG-GUID: PeJIs6rHPYxV7D03TWrzIpt-pQYWFpZF X-Proofpoint-Virus-Version: vendor=nai engine=6800 definitions=11740 signatures=596818 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=10 suspectscore=0 phishscore=0 adultscore=0 priorityscore=1501 spamscore=0 malwarescore=0 impostorscore=10 bulkscore=10 clxscore=1015 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2603250142 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 =20 #include #include "blk.h" @@ -1714,6 +1715,60 @@ void bio_check_pages_dirty(struct bio *bio) } EXPORT_SYMBOL_GPL(bio_check_pages_dirty); =20 +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) =3D { + .lock =3D 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 =3D this_cpu_ptr(&bio_complete_batch); + list =3D batch->list; + bio_list_init(&batch->list); + local_unlock_irq(&bio_complete_batch.lock); + + while (!bio_list_empty(&list)) { + struct bio *bio =3D bio_list_pop(&list); + bio->bi_end_io(bio); + } + + local_lock_irq(&bio_complete_batch.lock); + batch =3D 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 =3D 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 =20 - 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); =20 +/* + * Drain a dead CPU's deferred bio completions. The CPU is dead so no lock= ing + * 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 =3D per_cpu_ptr(&bio_complete_batch, cpu= ); + struct bio *bio; + + while ((bio =3D 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); } =20 + for_each_possible_cpu(i) { + struct bio_complete_batch *batch =3D + 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); =20 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 }; =20 --=20 2.39.5