From patchwork Mon Mar 29 02:00:26 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: 12169409 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,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 7979EC433DB for ; Mon, 29 Mar 2021 02:01:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 560F561922 for ; Mon, 29 Mar 2021 02:01:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231404AbhC2CAq (ORCPT ); Sun, 28 Mar 2021 22:00:46 -0400 Received: from mail-pf1-f178.google.com ([209.85.210.178]:38848 "EHLO mail-pf1-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230258AbhC2CAg (ORCPT ); Sun, 28 Mar 2021 22:00:36 -0400 Received: by mail-pf1-f178.google.com with SMTP id v10so3519886pfn.5 for ; Sun, 28 Mar 2021 19:00:36 -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=gGM6jgvygXQayKKXpltH+wuSVtpX58kW1xtKKOt7FrNgSBZWwhoQKGEn8DHIFVqnhV DXHILUEA0mm0aYwZtgYr/am7yPtnfKXKCTPDzu/9WyU11PTP/KSFt5OoRrzTdRBI/rGM T1GnWTPZb3IMkRFVmIlf27JtNaefOlSsG+RjF17SZCmTazZrvsDIfEd3kPj9aFuL1B4X MlPDReAvm0lAqpVY6AJaRiBD55MJPpWDPGeGSk337DkbDso+nTOKDNcAz5HpgDaXzSyv pJinB83ye7Oxe1QPwqnA6g15CKVgISfiAvvL+fvqMsjY9Mb+J+A/nhmFh3pPlSbDUbkE E15g== X-Gm-Message-State: AOAM530Blw4lEJ2bHf0MLlk9XSa5B1QyRCsayHdWHnbx7AWZyS4SzDvz C3so2LI4re5/KF+422cuEGg= X-Google-Smtp-Source: ABdhPJyHtpQ4o9m8FkxKLjcp0C3oFdghYDYetRE74oviWtRoB4HG0MwKL0u+pS7CwkLJretD2ehNOg== X-Received: by 2002:a63:1c4c:: with SMTP id c12mr21659191pgm.179.1616983236423; Sun, 28 Mar 2021 19:00:36 -0700 (PDT) Received: from asus.hsd1.ca.comcast.net ([2601:647:4000:d7:7123:9470:fec5:1a3a]) by smtp.gmail.com with ESMTPSA id x125sm15784979pfd.124.2021.03.28.19.00.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 28 Mar 2021 19:00:35 -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 v4 1/3] blk-mq: Move the elevator_exit() definition Date: Sun, 28 Mar 2021 19:00:26 -0700 Message-Id: <20210329020028.18241-2-bvanassche@acm.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210329020028.18241-1-bvanassche@acm.org> References: <20210329020028.18241-1-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 Mon Mar 29 02:00:27 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: 12169415 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,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 AEA12C433DB for ; Mon, 29 Mar 2021 02:01:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6C2A861927 for ; Mon, 29 Mar 2021 02:01:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231408AbhC2CBR (ORCPT ); Sun, 28 Mar 2021 22:01:17 -0400 Received: from mail-pg1-f173.google.com ([209.85.215.173]:33493 "EHLO mail-pg1-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230458AbhC2CAt (ORCPT ); Sun, 28 Mar 2021 22:00:49 -0400 Received: by mail-pg1-f173.google.com with SMTP id r17so8479763pgi.0 for ; Sun, 28 Mar 2021 19:00:38 -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=v63PUrNCVhsN9T+d4Vtkdw9Nq0HYnJrmTuXehSJt5JI=; b=KeDilxyDlIO8O6b5TfJ39eTR8xjHhMS5Knailbr2EwCQ3JEsENATJH07hRWDsZ1EbF FGotPb/Dz9ThZs050Lq6BGZXcOiN/W0cPhu6PgRoY/DXE1LB1Lm7Ylxe4f8tDmDBJULu B9eIfyhewwZKQo2tOFyW81IwG/uIPW9ra63Y7ESX23OZe2ZGj0pWcCaRzoNFsct2PXV0 XninusVSxA39StVxu6eHE+GFQJGdG7QeJ4lqsWuJOpP/Xkse5+oNZRTdbbqCMItsVmw0 uAzf3NL6R6DmoiP1qIHcDJxkF0H+o1/wBU+nVpVh29h9w/hi+8JJm3tXDV3SC55Jw3SN CazA== X-Gm-Message-State: AOAM530kg61i6MM/7NE5rA997mnrIWU7AcWwK29M4QWDJ8UgGSYr9cQP J4PxgiM+97TDJWB4s0cT7Aw= X-Google-Smtp-Source: ABdhPJzQh7veD8tEJnHs8ql4N9wENpQmaMAlEXwrnZzpg/EPPZ/aQvOCYbGQwuuAQJq5u2AZl2wfSg== X-Received: by 2002:a63:5c04:: with SMTP id q4mr21839213pgb.369.1616983238097; Sun, 28 Mar 2021 19:00:38 -0700 (PDT) Received: from asus.hsd1.ca.comcast.net ([2601:647:4000:d7:7123:9470:fec5:1a3a]) by smtp.gmail.com with ESMTPSA id x125sm15784979pfd.124.2021.03.28.19.00.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 28 Mar 2021 19:00:37 -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 v4 2/3] blk-mq: Introduce atomic variants of the tag iteration functions Date: Sun, 28 Mar 2021 19:00:27 -0700 Message-Id: <20210329020028.18241-3-bvanassche@acm.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210329020028.18241-1-bvanassche@acm.org> References: <20210329020028.18241-1-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)_iter' My conclusions from that analysis are as follows: - 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 | 38 +++++++++++++++++++++++++++++++++----- block/blk-mq-tag.h | 2 +- block/blk-mq.c | 2 +- drivers/scsi/hosts.c | 16 ++++++++-------- drivers/scsi/ufs/ufshcd.c | 4 ++-- include/linux/blk-mq.h | 2 ++ 6 files changed, 47 insertions(+), 17 deletions(-) diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index 9c92053e704d..3abfa4897ea2 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_atomic - 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; diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h index 7d3e6b333a4a..0290c308ece9 100644 --- a/block/blk-mq-tag.h +++ b/block/blk-mq-tag.h @@ -43,7 +43,7 @@ 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 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..5b170faa6318 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -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 Mon Mar 29 02:00:28 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: 12169413 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,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 7C67CC433E0 for ; Mon, 29 Mar 2021 02:01:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 66B5B61948 for ; Mon, 29 Mar 2021 02:01:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230209AbhC2CAq (ORCPT ); Sun, 28 Mar 2021 22:00:46 -0400 Received: from mail-pg1-f181.google.com ([209.85.215.181]:37503 "EHLO mail-pg1-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231381AbhC2CAk (ORCPT ); Sun, 28 Mar 2021 22:00:40 -0400 Received: by mail-pg1-f181.google.com with SMTP id 33so2571014pgy.4 for ; Sun, 28 Mar 2021 19:00:40 -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=5ptGtddf+iHZQ6SBXhNgC5lL8AaDfg1tJ4P7Xhuj5GQ=; b=cLvhxXuyL3ODNHBL6KBSa5yXhUzoWHdPhYeCqUOSSbSjQeuDuIJA2RmqAPM5TMjABG 3SAvHiJjhR/9UWeeUb4kfWeKJgWpO5Z/EdCHLJ22akthKU44OiJZMKdcb2DUIXmoib+e KpZqZYbCiZMBxCNmBJbArK8cbqI+xyai7caoLtX35RlMRwPn+MToY5a59CG1RJlX9G5V e2u+eLQGc/uKNeW4tQVGwa/HuRYayq93qZdlqytjjCJ9Bxlx2OmSU8MJKGw3+JizTGHQ fIn27Zku4zZf/bPms4ETcKS6BBwO5z5aTbMoc/eTHMtBpWu8MaP+Q/HqG10chodKpnMs Bn0Q== X-Gm-Message-State: AOAM530HyLUFKod55YlGkBjkiz3GGXIRH+ZVuZy/4WSvTcRgOC6Sbmkm WGt+k9hsondC31vh06A5iBo= X-Google-Smtp-Source: ABdhPJzy994C3zQQV3anWki5gFT9qOLnyP6x66mEiA9GbreEItdTxHYj3YueYtmZNAxgIQ1KtftRSA== X-Received: by 2002:a63:1144:: with SMTP id 4mr21625974pgr.333.1616983239707; Sun, 28 Mar 2021 19:00:39 -0700 (PDT) Received: from asus.hsd1.ca.comcast.net ([2601:647:4000:d7:7123:9470:fec5:1a3a]) by smtp.gmail.com with ESMTPSA id x125sm15784979pfd.124.2021.03.28.19.00.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 28 Mar 2021 19:00:39 -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 v4 3/3] blk-mq: Fix a race between iterating over requests and freeing requests Date: Sun, 28 Mar 2021 19:00:28 -0700 Message-Id: <20210329020028.18241-4-bvanassche@acm.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210329020028.18241-1-bvanassche@acm.org> References: <20210329020028.18241-1-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 | 41 +++++++++++++++++++++++++++++++++++++---- 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, 94 insertions(+), 10 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index fc60ff208497..400537dde675 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_iter - wait for preexisting __blk_mq_all_tag_iter() calls 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_iter(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_iter(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 3abfa4897ea2..c5e3d7716a5f 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); @@ -544,6 +576,7 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags, tags->nr_tags = total_tags; tags->nr_reserved_tags = reserved_tags; + init_rwsem(&tags->iter_rwsem); if (flags & BLK_MQ_F_TAG_HCTX_SHARED) return tags; diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h index 0290c308ece9..d1d73d7cc7df 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 5b170faa6318..8dc54976815f 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..85e0a59ef954 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_iter(struct blk_mq_tag_set *set); + /* * Internal elevator interface */ diff --git a/block/elevator.c b/block/elevator.c index 4b20d1ab29cc..70a10e31b336 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_iter(q->tag_set); blk_mq_sched_free_requests(q); __elevator_exit(q, e); }