From patchwork Fri Mar 26 02:29:17 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Bart Van Assche X-Patchwork-Id: 12165623 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6785EC433DB for ; Fri, 26 Mar 2021 02:30:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 30B856198C for ; Fri, 26 Mar 2021 02:30:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230327AbhCZC3v (ORCPT ); Thu, 25 Mar 2021 22:29:51 -0400 Received: from mail-pg1-f176.google.com ([209.85.215.176]:43714 "EHLO mail-pg1-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230269AbhCZC3b (ORCPT ); Thu, 25 Mar 2021 22:29:31 -0400 Received: by mail-pg1-f176.google.com with SMTP id u19so3606642pgh.10 for ; Thu, 25 Mar 2021 19:29:31 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=UYJRE/xreMdBfSedYAzb+UvnhwmwpqcZnYReZKFZZac=; b=sE+9U3KlmTI88DyWLSQVCTulxausiWch/MuunM/A5EnnFblgdewvcmnQaY7VCIBY0l 3eA8BEJAXDwAJokuFZgp4lYlBKpbopfZloGY5aBv/dnbdwVxYaMpxJQCAB+g6b+C/FwS ZyKc5xhK360UMTA+Xjg0x1x7MIIyfC5zO33x4ao48RL7qbdkJ7LbF/z59lCBpIHe3cDm cOcTfQKxxm5G+47Z/+FJbtvfHbYWlHfIGDTxuwLLDfTvV/igmTTUVHK9RgSPJhAhzOBH egHHB0B3A40C5+CSIG6lFzw4BupxR2/QzDlXGoPAd3YwSrCs42JshHUtMj/li8TPMh4f u+BA== X-Gm-Message-State: AOAM530idICCJDtLmkQwjAg5iby7sltNhOj4SjqTrxuxanBla/yp2cdb VVKMo/9E2/YOETZb60tj4d4= X-Google-Smtp-Source: ABdhPJyAaItDqZfBNDIDd5FgoTF+ZANHtNldBVmVsyOZbNj0nXFk+lDeImExbBNV51RdBtu6pskPQA== X-Received: by 2002:a63:4004:: with SMTP id n4mr10106234pga.287.1616725770674; Thu, 25 Mar 2021 19:29:30 -0700 (PDT) Received: from asus.hsd1.ca.comcast.net ([2601:647:4000:d7:c5af:7b7c:edac:ee67]) by smtp.gmail.com with ESMTPSA id v18sm7031135pfn.117.2021.03.25.19.29.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 25 Mar 2021 19:29:30 -0700 (PDT) From: Bart Van Assche To: Jens Axboe Cc: linux-block@vger.kernel.org, Christoph Hellwig , Bart Van Assche , Ming Lei , Hannes Reinecke , Johannes Thumshirn , John Garry , Khazhy Kumykov , Shin'ichiro Kawasaki Subject: [PATCH v3 1/3] blk-mq: Move the elevator_exit() definition Date: Thu, 25 Mar 2021 19:29:17 -0700 Message-Id: <20210326022919.19638-2-bvanassche@acm.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210326022919.19638-1-bvanassche@acm.org> References: <20210326022919.19638-1-bvanassche@acm.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Since elevator_exit() only has one caller, move its definition from block/blk.h into block/elevator.c. Remove the inline keyword since modern compilers are smart enough to decide when to inline functions that occur in the same compilation unit. Cc: Christoph Hellwig Cc: Ming Lei Cc: Hannes Reinecke Cc: Johannes Thumshirn Cc: John Garry Cc: Khazhy Kumykov Cc: Shin'ichiro Kawasaki Signed-off-by: Bart Van Assche --- block/blk.h | 9 --------- block/elevator.c | 8 ++++++++ 2 files changed, 8 insertions(+), 9 deletions(-) diff --git a/block/blk.h b/block/blk.h index 3b53e44b967e..e0a4a7577f6c 100644 --- a/block/blk.h +++ b/block/blk.h @@ -198,15 +198,6 @@ void __elevator_exit(struct request_queue *, struct elevator_queue *); int elv_register_queue(struct request_queue *q, bool uevent); void elv_unregister_queue(struct request_queue *q); -static inline void elevator_exit(struct request_queue *q, - struct elevator_queue *e) -{ - lockdep_assert_held(&q->sysfs_lock); - - blk_mq_sched_free_requests(q); - __elevator_exit(q, e); -} - ssize_t part_size_show(struct device *dev, struct device_attribute *attr, char *buf); ssize_t part_stat_show(struct device *dev, struct device_attribute *attr, diff --git a/block/elevator.c b/block/elevator.c index 293c5c81397a..4b20d1ab29cc 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -197,6 +197,14 @@ void __elevator_exit(struct request_queue *q, struct elevator_queue *e) kobject_put(&e->kobj); } +static void elevator_exit(struct request_queue *q, struct elevator_queue *e) +{ + lockdep_assert_held(&q->sysfs_lock); + + blk_mq_sched_free_requests(q); + __elevator_exit(q, e); +} + static inline void __elv_rqhash_del(struct request *rq) { hash_del(&rq->hash); From patchwork Fri Mar 26 02:29:18 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Bart Van Assche X-Patchwork-Id: 12165625 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B567DC433E3 for ; Fri, 26 Mar 2021 02:30:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 95B4561A4A for ; Fri, 26 Mar 2021 02:30:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230269AbhCZC3v (ORCPT ); Thu, 25 Mar 2021 22:29:51 -0400 Received: from mail-pj1-f51.google.com ([209.85.216.51]:43913 "EHLO mail-pj1-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230295AbhCZC3c (ORCPT ); Thu, 25 Mar 2021 22:29:32 -0400 Received: by mail-pj1-f51.google.com with SMTP id x21-20020a17090a5315b029012c4a622e4aso1009122pjh.2 for ; Thu, 25 Mar 2021 19:29:32 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=BzWsFa5Wc88vUiCthq0YfkpdZpJxNdXplIDligZF2co=; b=mS8tu7Mkq+nyEZqUTyCQcenGsetFpSlMLM8MUrmXhQQFgZxiUgmmRApjX7b8JLFa9J Jd1cwDDXnh1b+Np7h9XvIUNV7aKIXXCBxkzkQHucwQE7X7v0C/k8kwE87STPQssX1jlK reVCQNFGOjIn/lf+K93/xDLefJPF8HBh1YSXq7esHf5CPTvC8rCLJSjluKQfIByFciRY fE2aU4pMzygZJ22SEjRjtLtsv7aM26c2OXKF/6JmhRUUChn1eiLk8fwSoWvuRv4a46kX rzhYFsXeUCZrlpIC4Xk+2tUWCOC0RrV0JoQWiVYsxXJSfU7XiYqjwc5VXZLC6lpG83cR UyjA== X-Gm-Message-State: AOAM530da44JvT+QhisOMPcKX4npAzg5HRopW2AxA5cXUP81/uDLPt+B /w6XRrnvPuiXxq3OMfp911I= X-Google-Smtp-Source: ABdhPJx6Iyz36izCYahKN6gizdwa4XjB6z5fqN4RfCwdNJAVeumDEIbbdFDYgfGgbZQnWs95RjZ1Zw== X-Received: by 2002:a17:902:c394:b029:e7:1029:8de3 with SMTP id g20-20020a170902c394b02900e710298de3mr12675372plg.72.1616725772411; Thu, 25 Mar 2021 19:29:32 -0700 (PDT) Received: from asus.hsd1.ca.comcast.net ([2601:647:4000:d7:c5af:7b7c:edac:ee67]) by smtp.gmail.com with ESMTPSA id v18sm7031135pfn.117.2021.03.25.19.29.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 25 Mar 2021 19:29:31 -0700 (PDT) From: Bart Van Assche To: Jens Axboe Cc: linux-block@vger.kernel.org, Christoph Hellwig , Bart Van Assche , "Martin K . Petersen" , Ming Lei , Hannes Reinecke , Johannes Thumshirn , John Garry , Khazhy Kumykov , Shin'ichiro Kawasaki Subject: [PATCH v3 2/3] blk-mq: Introduce atomic variants of the tag iteration functions Date: Thu, 25 Mar 2021 19:29:18 -0700 Message-Id: <20210326022919.19638-3-bvanassche@acm.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210326022919.19638-1-bvanassche@acm.org> References: <20210326022919.19638-1-bvanassche@acm.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Since in the next patch knowledge is required of whether or not it is allowed to sleep inside the tag iteration functions, pass this context information to the tag iteration functions. I have reviewed all callers of tag iteration functions to verify these annotations by starting from the output of the following grep command: git grep -nHE 'blk_mq_(all_tag|tagset_busy|queue_tag_busy)_iter' My conclusions from that analysis are as follows: - The callback functions passed to blk_mq_queue_tag_busy_iter() from the block layer core do not sleep except the block driver timeout handler. - Sleeping is allowed in the blk-mq-debugfs code that iterates over tags. - Since the blk_mq_tagset_busy_iter() calls in the mtip32xx driver are preceded by a function that sleeps (blk_mq_quiesce_queue()), sleeping is safe in the context of the blk_mq_tagset_busy_iter() calls. - The same reasoning also applies to the nbd driver. - All blk_mq_tagset_busy_iter() calls in the NVMe drivers are followed by a call to a function that sleeps so sleeping inside blk_mq_tagset_busy_iter() when called from the NVMe driver is fine. - scsi_host_busy(), scsi_host_complete_all_commands() and scsi_host_busy_iter() are used by multiple SCSI LLDs so analyzing whether or not these functions may sleep is hard. Instead of performing that analysis, make it safe to call these functions from atomic context. Cc: Martin K. Petersen Cc: Christoph Hellwig Cc: Ming Lei Cc: Hannes Reinecke Cc: Johannes Thumshirn Cc: John Garry Cc: Khazhy Kumykov Cc: Shin'ichiro Kawasaki Signed-off-by: Bart Van Assche --- block/blk-mq-tag.c | 44 ++++++++++++++++++++++++++++++++------- block/blk-mq-tag.h | 4 ++-- block/blk-mq.c | 10 ++++----- drivers/scsi/hosts.c | 16 +++++++------- drivers/scsi/ufs/ufshcd.c | 4 ++-- include/linux/blk-mq.h | 2 ++ 6 files changed, 56 insertions(+), 24 deletions(-) diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index e5bfecf2940d..975626f755c2 100644 --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -322,18 +322,19 @@ static void __blk_mq_all_tag_iter(struct blk_mq_tags *tags, } /** - * blk_mq_all_tag_iter - iterate over all requests in a tag map + * blk_mq_all_tag_iter_atomic - iterate over all requests in a tag map * @tags: Tag map to iterate over. * @fn: Pointer to the function that will be called for each * request. @fn will be called as follows: @fn(rq, @priv, * reserved) where rq is a pointer to a request. 'reserved' * indicates whether or not @rq is a reserved request. Return - * true to continue iterating tags, false to stop. + * true to continue iterating tags, false to stop. Must not + * sleep. * @priv: Will be passed as second argument to @fn. * - * Caller has to pass the tag map from which requests are allocated. + * Does not sleep. */ -void blk_mq_all_tag_iter(struct blk_mq_tags *tags, busy_tag_iter_fn *fn, +void blk_mq_all_tag_iter_atomic(struct blk_mq_tags *tags, busy_tag_iter_fn *fn, void *priv) { __blk_mq_all_tag_iter(tags, fn, priv, BT_TAG_ITER_STATIC_RQS); @@ -348,6 +349,8 @@ void blk_mq_all_tag_iter(struct blk_mq_tags *tags, busy_tag_iter_fn *fn, * indicates whether or not @rq is a reserved request. Return * true to continue iterating tags, false to stop. * @priv: Will be passed as second argument to @fn. + * + * May sleep. */ void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset, busy_tag_iter_fn *fn, void *priv) @@ -362,6 +365,31 @@ void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset, } EXPORT_SYMBOL(blk_mq_tagset_busy_iter); +/** + * blk_mq_tagset_busy_iter - iterate over all started requests in a tag set + * @tagset: Tag set to iterate over. + * @fn: Pointer to the function that will be called for each started + * request. @fn will be called as follows: @fn(rq, @priv, + * reserved) where rq is a pointer to a request. 'reserved' + * indicates whether or not @rq is a reserved request. Return + * true to continue iterating tags, false to stop. Must not sleep. + * @priv: Will be passed as second argument to @fn. + * + * Does not sleep. + */ +void blk_mq_tagset_busy_iter_atomic(struct blk_mq_tag_set *tagset, + busy_tag_iter_fn *fn, void *priv) +{ + int i; + + for (i = 0; i < tagset->nr_hw_queues; i++) { + if (tagset->tags && tagset->tags[i]) + __blk_mq_all_tag_iter(tagset->tags[i], fn, priv, + BT_TAG_ITER_STARTED); + } +} +EXPORT_SYMBOL(blk_mq_tagset_busy_iter_atomic); + static bool blk_mq_tagset_count_completed_rqs(struct request *rq, void *data, bool reserved) { @@ -384,7 +412,7 @@ void blk_mq_tagset_wait_completed_request(struct blk_mq_tag_set *tagset) while (true) { unsigned count = 0; - blk_mq_tagset_busy_iter(tagset, + blk_mq_tagset_busy_iter_atomic(tagset, blk_mq_tagset_count_completed_rqs, &count); if (!count) break; @@ -400,15 +428,17 @@ EXPORT_SYMBOL(blk_mq_tagset_wait_completed_request); * on @q. @fn will be called as follows: @fn(hctx, rq, @priv, * reserved) where rq is a pointer to a request and hctx points * to the hardware queue associated with the request. 'reserved' - * indicates whether or not @rq is a reserved request. + * indicates whether or not @rq is a reserved request. Must not + * sleep if @in_atomic_context is %true. * @priv: Will be passed as third argument to @fn. + * @in_atomic_context: If true, do not sleep. * * Note: if @q->tag_set is shared with other request queues then @fn will be * called for all requests on all queues that share that tag set and not only * for requests associated with @q. */ void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn, - void *priv) + void *priv, bool in_atomic_context) { struct blk_mq_hw_ctx *hctx; int i; diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h index 7d3e6b333a4a..b01c806e4c2d 100644 --- a/block/blk-mq-tag.h +++ b/block/blk-mq-tag.h @@ -42,8 +42,8 @@ extern void blk_mq_tag_resize_shared_sbitmap(struct blk_mq_tag_set *set, extern void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool); void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn, - void *priv); -void blk_mq_all_tag_iter(struct blk_mq_tags *tags, busy_tag_iter_fn *fn, + void *priv, bool in_atomic_context); +void blk_mq_all_tag_iter_atomic(struct blk_mq_tags *tags, busy_tag_iter_fn *fn, void *priv); static inline struct sbq_wait_state *bt_wait_ptr(struct sbitmap_queue *bt, diff --git a/block/blk-mq.c b/block/blk-mq.c index d4d7c1caa439..203caa14c51a 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -117,7 +117,7 @@ unsigned int blk_mq_in_flight(struct request_queue *q, { struct mq_inflight mi = { .part = part }; - blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight, &mi); + blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight, &mi, true); return mi.inflight[0] + mi.inflight[1]; } @@ -127,7 +127,7 @@ void blk_mq_in_flight_rw(struct request_queue *q, struct block_device *part, { struct mq_inflight mi = { .part = part }; - blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight, &mi); + blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight, &mi, true); inflight[0] = mi.inflight[0]; inflight[1] = mi.inflight[1]; } @@ -868,7 +868,7 @@ bool blk_mq_queue_inflight(struct request_queue *q) { bool busy = false; - blk_mq_queue_tag_busy_iter(q, blk_mq_rq_inflight, &busy); + blk_mq_queue_tag_busy_iter(q, blk_mq_rq_inflight, &busy, true); return busy; } EXPORT_SYMBOL_GPL(blk_mq_queue_inflight); @@ -973,7 +973,7 @@ static void blk_mq_timeout_work(struct work_struct *work) if (!percpu_ref_tryget(&q->q_usage_counter)) return; - blk_mq_queue_tag_busy_iter(q, blk_mq_check_expired, &next); + blk_mq_queue_tag_busy_iter(q, blk_mq_check_expired, &next, false); if (next != 0) { mod_timer(&q->timeout, next); @@ -2483,7 +2483,7 @@ static bool blk_mq_hctx_has_requests(struct blk_mq_hw_ctx *hctx) .hctx = hctx, }; - blk_mq_all_tag_iter(tags, blk_mq_has_request, &data); + blk_mq_all_tag_iter_atomic(tags, blk_mq_has_request, &data); return data.has_rq; } diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c index 2f162603876f..f09e1520a241 100644 --- a/drivers/scsi/hosts.c +++ b/drivers/scsi/hosts.c @@ -578,8 +578,8 @@ int scsi_host_busy(struct Scsi_Host *shost) { int cnt = 0; - blk_mq_tagset_busy_iter(&shost->tag_set, - scsi_host_check_in_flight, &cnt); + blk_mq_tagset_busy_iter_atomic(&shost->tag_set, + scsi_host_check_in_flight, &cnt); return cnt; } EXPORT_SYMBOL(scsi_host_busy); @@ -677,8 +677,8 @@ static bool complete_all_cmds_iter(struct request *rq, void *data, bool rsvd) */ void scsi_host_complete_all_commands(struct Scsi_Host *shost, int status) { - blk_mq_tagset_busy_iter(&shost->tag_set, complete_all_cmds_iter, - &status); + blk_mq_tagset_busy_iter_atomic(&shost->tag_set, complete_all_cmds_iter, + &status); } EXPORT_SYMBOL_GPL(scsi_host_complete_all_commands); @@ -699,11 +699,11 @@ static bool __scsi_host_busy_iter_fn(struct request *req, void *priv, /** * scsi_host_busy_iter - Iterate over all busy commands * @shost: Pointer to Scsi_Host. - * @fn: Function to call on each busy command + * @fn: Function to call on each busy command. Must not sleep. * @priv: Data pointer passed to @fn * * If locking against concurrent command completions is required - * ithas to be provided by the caller + * it has to be provided by the caller. **/ void scsi_host_busy_iter(struct Scsi_Host *shost, bool (*fn)(struct scsi_cmnd *, void *, bool), @@ -714,7 +714,7 @@ void scsi_host_busy_iter(struct Scsi_Host *shost, .priv = priv, }; - blk_mq_tagset_busy_iter(&shost->tag_set, __scsi_host_busy_iter_fn, - &iter_data); + blk_mq_tagset_busy_iter_atomic(&shost->tag_set, + __scsi_host_busy_iter_fn, &iter_data); } EXPORT_SYMBOL_GPL(scsi_host_busy_iter); diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c index c86760788c72..6d2f8f18e2a3 100644 --- a/drivers/scsi/ufs/ufshcd.c +++ b/drivers/scsi/ufs/ufshcd.c @@ -1380,7 +1380,7 @@ static bool ufshcd_any_tag_in_use(struct ufs_hba *hba) struct request_queue *q = hba->cmd_queue; int busy = 0; - blk_mq_tagset_busy_iter(q->tag_set, ufshcd_is_busy, &busy); + blk_mq_tagset_busy_iter_atomic(q->tag_set, ufshcd_is_busy, &busy); return busy; } @@ -6269,7 +6269,7 @@ static irqreturn_t ufshcd_tmc_handler(struct ufs_hba *hba) .pending = ufshcd_readl(hba, REG_UTP_TASK_REQ_DOOR_BELL), }; - blk_mq_tagset_busy_iter(q->tag_set, ufshcd_compl_tm, &ci); + blk_mq_tagset_busy_iter_atomic(q->tag_set, ufshcd_compl_tm, &ci); return ci.ncpl ? IRQ_HANDLED : IRQ_NONE; } diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index 2c473c9b8990..dfa0114a49fd 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -526,6 +526,8 @@ void blk_mq_run_hw_queues(struct request_queue *q, bool async); void blk_mq_delay_run_hw_queues(struct request_queue *q, unsigned long msecs); void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset, busy_tag_iter_fn *fn, void *priv); +void blk_mq_tagset_busy_iter_atomic(struct blk_mq_tag_set *tagset, + busy_tag_iter_fn *fn, void *priv); void blk_mq_tagset_wait_completed_request(struct blk_mq_tag_set *tagset); void blk_mq_freeze_queue(struct request_queue *q); void blk_mq_unfreeze_queue(struct request_queue *q); From patchwork Fri Mar 26 02:29:19 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Bart Van Assche X-Patchwork-Id: 12165627 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9A24AC433E1 for ; Fri, 26 Mar 2021 02:30:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 677A061A45 for ; Fri, 26 Mar 2021 02:30:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230345AbhCZC3v (ORCPT ); Thu, 25 Mar 2021 22:29:51 -0400 Received: from mail-pl1-f176.google.com ([209.85.214.176]:44657 "EHLO mail-pl1-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230311AbhCZC3e (ORCPT ); Thu, 25 Mar 2021 22:29:34 -0400 Received: by mail-pl1-f176.google.com with SMTP id d8so185327plh.11 for ; Thu, 25 Mar 2021 19:29:34 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=sgTClXYlnUboBozzSUhj4AA1Wf2J+HIz/s9O+TGi2hE=; b=Hh9JWHx3JHNyHl836F8/IWoEVFY+QloCBpq3y4A0qeMvMUjdgca40O0XmNc+o7SjPc MifD6YLTeXBerhH45lhTIMpyAKeL2H81COpKvZLIXL9ZvQY3P3cU0Qkf1mlqntKkU/1Y bawbD81Qepcq8Z5a+c1nt54ZO8InJ1oYJEV3fZqDJFpyKU8JLnIrSmNQDejgONHC9a7T n5sJMXWpkLDqN34xsdmpvGnyoyPgWHsUeYY1hZ+gR9l9ZBu2yj/QP+DRL63htoTq8DXr ksHinNuNpYeMA0DW6+B963uZImAblErlmiYRFD1zwufLn70paELsPyEcqrUcDZLhV7ks AP8g== X-Gm-Message-State: AOAM533fNviGBi3MhX2YeK9Gy3Yj+pcS5zX5urZiTIx4GgelNkeM1Of2 iMcw8+2URpWx6mYIyABXmRc= X-Google-Smtp-Source: ABdhPJzC+j+git9dgG36aomOR3Th4gHbySjByCzUKLY90tfdEISU7VnDWChFPuatL3s2GpkZQ9dgVQ== X-Received: by 2002:a17:902:eec4:b029:e5:e6af:825c with SMTP id h4-20020a170902eec4b02900e5e6af825cmr13123572plb.73.1616725774059; Thu, 25 Mar 2021 19:29:34 -0700 (PDT) Received: from asus.hsd1.ca.comcast.net ([2601:647:4000:d7:c5af:7b7c:edac:ee67]) by smtp.gmail.com with ESMTPSA id v18sm7031135pfn.117.2021.03.25.19.29.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 25 Mar 2021 19:29:33 -0700 (PDT) From: Bart Van Assche To: Jens Axboe Cc: linux-block@vger.kernel.org, Christoph Hellwig , Bart Van Assche , Ming Lei , Hannes Reinecke , Johannes Thumshirn , John Garry , Khazhy Kumykov , Shin'ichiro Kawasaki Subject: [PATCH v3 3/3] blk-mq: Fix a race between iterating over requests and freeing requests Date: Thu, 25 Mar 2021 19:29:19 -0700 Message-Id: <20210326022919.19638-4-bvanassche@acm.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210326022919.19638-1-bvanassche@acm.org> References: <20210326022919.19638-1-bvanassche@acm.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org When multiple request queues share a tag set and when switching the I/O scheduler for one of the request queues associated with that tag set, the following race can happen: * blk_mq_tagset_busy_iter() calls bt_tags_iter() and bt_tags_iter() assigns a pointer to a scheduler request to the local variable 'rq'. * blk_mq_sched_free_requests() is called to free hctx->sched_tags. * blk_mq_tagset_busy_iter() dereferences 'rq' and triggers a use-after-free. Fix this race as follows: * Use rcu_assign_pointer() and rcu_dereference() to access hctx->tags->rqs[]. The performance impact of the assignments added to the hot path is minimal (about 1% according to one particular test). * Protect hctx->tags->rqs[] reads with an RCU read-side lock or with a semaphore. Which mechanism is used depends on whether or not it is allowed to sleep and also on whether or not the callback function may sleep. * Wait for all preexisting readers to finish before freeing scheduler requests. Multiple users have reported use-after-free complaints similar to the following (from https://lore.kernel.org/linux-block/1545261885.185366.488.camel@acm.org/): BUG: KASAN: use-after-free in bt_iter+0x86/0xf0 Read of size 8 at addr ffff88803b335240 by task fio/21412 CPU: 0 PID: 21412 Comm: fio Tainted: G W 4.20.0-rc6-dbg+ #3 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 Call Trace: dump_stack+0x86/0xca print_address_description+0x71/0x239 kasan_report.cold.5+0x242/0x301 __asan_load8+0x54/0x90 bt_iter+0x86/0xf0 blk_mq_queue_tag_busy_iter+0x373/0x5e0 blk_mq_in_flight+0x96/0xb0 part_in_flight+0x40/0x140 part_round_stats+0x18e/0x370 blk_account_io_start+0x3d7/0x670 blk_mq_bio_to_request+0x19c/0x3a0 blk_mq_make_request+0x7a9/0xcb0 generic_make_request+0x41d/0x960 submit_bio+0x9b/0x250 do_blockdev_direct_IO+0x435c/0x4c70 __blockdev_direct_IO+0x79/0x88 ext4_direct_IO+0x46c/0xc00 generic_file_direct_write+0x119/0x210 __generic_file_write_iter+0x11c/0x280 ext4_file_write_iter+0x1b8/0x6f0 aio_write+0x204/0x310 io_submit_one+0x9d3/0xe80 __x64_sys_io_submit+0x115/0x340 do_syscall_64+0x71/0x210 Cc: Christoph Hellwig Cc: Ming Lei Cc: Hannes Reinecke Cc: Johannes Thumshirn Cc: John Garry Cc: Khazhy Kumykov Cc: Shin'ichiro Kawasaki Signed-off-by: Bart Van Assche --- block/blk-core.c | 34 +++++++++++++++++++++++++++++++++- block/blk-mq-tag.c | 43 +++++++++++++++++++++++++++++++++++++++---- block/blk-mq-tag.h | 4 +++- block/blk-mq.c | 21 +++++++++++++++++---- block/blk-mq.h | 1 + block/blk.h | 2 ++ block/elevator.c | 1 + 7 files changed, 96 insertions(+), 10 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index fc60ff208497..fabb45ecd216 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -279,6 +279,36 @@ void blk_dump_rq_flags(struct request *rq, char *msg) } EXPORT_SYMBOL(blk_dump_rq_flags); +/** + * blk_mq_wait_for_tag_readers - wait for preexisting tag readers to finish + * @set: Tag set to wait on. + * + * Waits for preexisting __blk_mq_all_tag_iter() calls to finish accessing + * hctx->tags->rqs[]. New readers may start while this function is in progress + * or after this function has returned. Use this function to make sure that + * hctx->tags->rqs[] changes have become globally visible. + * + * Accesses of hctx->tags->rqs[] by blk_mq_queue_tag_busy_iter() calls are out + * of scope for this function. The caller can pause blk_mq_queue_tag_busy_iter() + * calls for a request queue by freezing that request queue. + */ +void blk_mq_wait_for_tag_readers(struct blk_mq_tag_set *set) +{ + struct blk_mq_tags *tags; + int i; + + if (set->tags) { + for (i = 0; i < set->nr_hw_queues; i++) { + tags = set->tags[i]; + if (!tags) + continue; + down_write(&tags->iter_rwsem); + up_write(&tags->iter_rwsem); + } + } + synchronize_rcu(); +} + /** * blk_sync_queue - cancel any pending callbacks on a queue * @q: the queue @@ -412,8 +442,10 @@ void blk_cleanup_queue(struct request_queue *q) * it is safe to free requests now. */ mutex_lock(&q->sysfs_lock); - if (q->elevator) + if (q->elevator) { + blk_mq_wait_for_tag_readers(q->tag_set); blk_mq_sched_free_requests(q); + } mutex_unlock(&q->sysfs_lock); percpu_ref_exit(&q->q_usage_counter); diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index 975626f755c2..c8722ce7c35c 100644 --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -209,7 +209,12 @@ static bool bt_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data) if (!reserved) bitnr += tags->nr_reserved_tags; - rq = tags->rqs[bitnr]; + /* + * See also the percpu_ref_tryget() and blk_queue_exit() calls in + * blk_mq_queue_tag_busy_iter(). + */ + rq = rcu_dereference_check(tags->rqs[bitnr], + !percpu_ref_is_zero(&hctx->queue->q_usage_counter)); /* * We can hit rq == NULL here, because the tagging functions @@ -254,11 +259,17 @@ struct bt_tags_iter_data { unsigned int flags; }; +/* Include reserved tags. */ #define BT_TAG_ITER_RESERVED (1 << 0) +/* Only include started requests. */ #define BT_TAG_ITER_STARTED (1 << 1) +/* Iterate over tags->static_rqs[] instead of tags->rqs[]. */ #define BT_TAG_ITER_STATIC_RQS (1 << 2) +/* The callback function may sleep. */ +#define BT_TAG_ITER_MAY_SLEEP (1 << 3) -static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data) +static bool __bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, + void *data) { struct bt_tags_iter_data *iter_data = data; struct blk_mq_tags *tags = iter_data->tags; @@ -275,7 +286,7 @@ static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data) if (iter_data->flags & BT_TAG_ITER_STATIC_RQS) rq = tags->static_rqs[bitnr]; else - rq = tags->rqs[bitnr]; + rq = rcu_dereference_check(tags->rqs[bitnr], true); if (!rq) return true; if ((iter_data->flags & BT_TAG_ITER_STARTED) && @@ -284,6 +295,25 @@ static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data) return iter_data->fn(rq, iter_data->data, reserved); } +static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data) +{ + struct bt_tags_iter_data *iter_data = data; + struct blk_mq_tags *tags = iter_data->tags; + bool res; + + if (iter_data->flags & BT_TAG_ITER_MAY_SLEEP) { + down_read(&tags->iter_rwsem); + res = __bt_tags_iter(bitmap, bitnr, data); + up_read(&tags->iter_rwsem); + } else { + rcu_read_lock(); + res = __bt_tags_iter(bitmap, bitnr, data); + rcu_read_unlock(); + } + + return res; +} + /** * bt_tags_for_each - iterate over the requests in a tag map * @tags: Tag map to iterate over. @@ -357,10 +387,12 @@ void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset, { int i; + might_sleep(); + for (i = 0; i < tagset->nr_hw_queues; i++) { if (tagset->tags && tagset->tags[i]) __blk_mq_all_tag_iter(tagset->tags[i], fn, priv, - BT_TAG_ITER_STARTED); + BT_TAG_ITER_STARTED | BT_TAG_ITER_MAY_SLEEP); } } EXPORT_SYMBOL(blk_mq_tagset_busy_iter); @@ -554,6 +586,9 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags, kfree(tags); return NULL; } + + init_rwsem(&tags->iter_rwsem); + return tags; } diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h index b01c806e4c2d..534377385456 100644 --- a/block/blk-mq-tag.h +++ b/block/blk-mq-tag.h @@ -17,9 +17,11 @@ struct blk_mq_tags { struct sbitmap_queue __bitmap_tags; struct sbitmap_queue __breserved_tags; - struct request **rqs; + struct request __rcu **rqs; struct request **static_rqs; struct list_head page_list; + + struct rw_semaphore iter_rwsem; }; extern struct blk_mq_tags *blk_mq_init_tags(unsigned int nr_tags, diff --git a/block/blk-mq.c b/block/blk-mq.c index 203caa14c51a..e66357da6c6b 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -495,8 +495,10 @@ static void __blk_mq_free_request(struct request *rq) blk_crypto_free_request(rq); blk_pm_mark_last_busy(rq); rq->mq_hctx = NULL; - if (rq->tag != BLK_MQ_NO_TAG) + if (rq->tag != BLK_MQ_NO_TAG) { blk_mq_put_tag(hctx->tags, ctx, rq->tag); + rcu_assign_pointer(hctx->tags->rqs[rq->tag], NULL); + } if (sched_tag != BLK_MQ_NO_TAG) blk_mq_put_tag(hctx->sched_tags, ctx, sched_tag); blk_mq_sched_restart(hctx); @@ -838,9 +840,20 @@ EXPORT_SYMBOL(blk_mq_delay_kick_requeue_list); struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags, unsigned int tag) { + struct request *rq; + if (tag < tags->nr_tags) { - prefetch(tags->rqs[tag]); - return tags->rqs[tag]; + /* + * Freeing tags happens with the request queue frozen so the + * srcu dereference below is protected by the request queue + * usage count. We can only verify that usage count after + * having read the request pointer. + */ + rq = rcu_dereference_check(tags->rqs[tag], true); + WARN_ON_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && rq && + percpu_ref_is_zero(&rq->q->q_usage_counter)); + prefetch(rq); + return rq; } return NULL; @@ -1111,7 +1124,7 @@ static bool blk_mq_get_driver_tag(struct request *rq) rq->rq_flags |= RQF_MQ_INFLIGHT; __blk_mq_inc_active_requests(hctx); } - hctx->tags->rqs[rq->tag] = rq; + rcu_assign_pointer(hctx->tags->rqs[rq->tag], rq); return true; } diff --git a/block/blk-mq.h b/block/blk-mq.h index 3616453ca28c..9ccb1818303b 100644 --- a/block/blk-mq.h +++ b/block/blk-mq.h @@ -226,6 +226,7 @@ static inline void __blk_mq_put_driver_tag(struct blk_mq_hw_ctx *hctx, struct request *rq) { blk_mq_put_tag(hctx->tags, rq->mq_ctx, rq->tag); + rcu_assign_pointer(hctx->tags->rqs[rq->tag], NULL); rq->tag = BLK_MQ_NO_TAG; if (rq->rq_flags & RQF_MQ_INFLIGHT) { diff --git a/block/blk.h b/block/blk.h index e0a4a7577f6c..825ae70c7c0b 100644 --- a/block/blk.h +++ b/block/blk.h @@ -184,6 +184,8 @@ bool blk_bio_list_merge(struct request_queue *q, struct list_head *list, void blk_account_io_start(struct request *req); void blk_account_io_done(struct request *req, u64 now); +void blk_mq_wait_for_tag_readers(struct blk_mq_tag_set *set); + /* * Internal elevator interface */ diff --git a/block/elevator.c b/block/elevator.c index 4b20d1ab29cc..28edcb3f7ceb 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -201,6 +201,7 @@ static void elevator_exit(struct request_queue *q, struct elevator_queue *e) { lockdep_assert_held(&q->sysfs_lock); + blk_mq_wait_for_tag_readers(q->tag_set); blk_mq_sched_free_requests(q); __elevator_exit(q, e); }