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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 69F01E77198 for ; Tue, 7 Jan 2025 06:31:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=td9hXTRm3bIkt4nDSZFirDvnCCVcnWUnxIQRddOHupE=; b=LJxXpNebzzxpfzLD26EmoS3dKx h5ekf9E2IkJst5W69MB/vgRUXqy3FC31I+Eka+8TRwVlNaRdD7l0XcybeJCLj+Syv4VSTe9ToQBCL uTR5YJrxeZsshCPEn341BGIpVmeHcotHgArzbTFyaB22h901PTvATO1pfQP3DYbd3VqfzMi7+8zv5 b0OmKGBnpLwczVZ2XytAdSIE58FOA1jxFJftqorSeOt2ysk7j6RkTg8CutyFjRfPQtE9yX2l9ZZxH oZr3C+KUHcZuSoPh61BNMA5ZMC+dvRQmfAGXDigtjjlW6MBKKTguMC25j8q2xoTb9j264GyjwhJla GVdCn/hg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tV37l-00000003dtv-1yQQ; Tue, 07 Jan 2025 06:31:33 +0000 Received: from 2a02-8389-2341-5b80-d467-d75d-35bf-0eb6.cable.dynamic.v6.surfer.at ([2a02:8389:2341:5b80:d467:d75d:35bf:eb6] helo=localhost) by bombadil.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1tV37j-00000003ds7-1Qz0; Tue, 07 Jan 2025 06:31:31 +0000 From: Christoph Hellwig To: Jens Axboe Cc: Damien Le Moal , Ming Lei , Nilay Shroff , linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, nbd@other.debian.org, linux-scsi@vger.kernel.org, usb-storage@lists.one-eyed-alien.net Subject: [PATCH 3/8] block: don't update BLK_FEAT_POLL in __blk_mq_update_nr_hw_queues Date: Tue, 7 Jan 2025 07:30:35 +0100 Message-ID: <20250107063120.1011593-4-hch@lst.de> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20250107063120.1011593-1-hch@lst.de> References: <20250107063120.1011593-1-hch@lst.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org When __blk_mq_update_nr_hw_queues changes the number of tag sets, it might have to disable poll queues. Currently it does so by adjusting the BLK_FEAT_POLL, which is a bit against the intent of features that describe hardware / driver capabilities, but more importantly causes nasty lock order problems with the broadly held freeze when updating the number of hardware queues and the limits lock. Fix this by leaving BLK_FEAT_POLL alone, and instead check for the number of poll queues in the bio submission and poll handlers. While this adds extra work to the fast path, the variables are in cache lines used by these operations anyway, so it should be cheap enough. Fixes: 8023e144f9d6 ("block: move the poll flag to queue_limits") Signed-off-by: Christoph Hellwig --- block/blk-core.c | 17 ++++++++++++++--- block/blk-mq.c | 17 +---------------- 2 files changed, 15 insertions(+), 19 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index 666efe8fa202..bd5bec843d37 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -753,6 +753,18 @@ static blk_status_t blk_validate_atomic_write_op_size(struct request_queue *q, return BLK_STS_OK; } +static bool bdev_can_poll(struct block_device *bdev) +{ + struct request_queue *q = bdev_get_queue(bdev); + + if (!(q->limits.features & BLK_FEAT_POLL)) + return false; + + if (queue_is_mq(q)) + return q->tag_set->map[HCTX_TYPE_POLL].nr_queues; + return true; +} + /** * submit_bio_noacct - re-submit a bio to the block device layer for I/O * @bio: The bio describing the location in memory and on the device. @@ -805,8 +817,7 @@ void submit_bio_noacct(struct bio *bio) } } - if (!(q->limits.features & BLK_FEAT_POLL) && - (bio->bi_opf & REQ_POLLED)) { + if ((bio->bi_opf & REQ_POLLED) && !bdev_can_poll(bdev)) { bio_clear_polled(bio); goto not_supported; } @@ -935,7 +946,7 @@ int bio_poll(struct bio *bio, struct io_comp_batch *iob, unsigned int flags) return 0; q = bdev_get_queue(bdev); - if (cookie == BLK_QC_T_NONE || !(q->limits.features & BLK_FEAT_POLL)) + if (cookie == BLK_QC_T_NONE || !bdev_can_poll(bdev)) return 0; blk_flush_plug(current->plug, false); diff --git a/block/blk-mq.c b/block/blk-mq.c index 2e6132f778fd..f795d81b6b38 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -4320,12 +4320,6 @@ void blk_mq_release(struct request_queue *q) blk_mq_sysfs_deinit(q); } -static bool blk_mq_can_poll(struct blk_mq_tag_set *set) -{ - return set->nr_maps > HCTX_TYPE_POLL && - set->map[HCTX_TYPE_POLL].nr_queues; -} - struct request_queue *blk_mq_alloc_queue(struct blk_mq_tag_set *set, struct queue_limits *lim, void *queuedata) { @@ -4336,7 +4330,7 @@ struct request_queue *blk_mq_alloc_queue(struct blk_mq_tag_set *set, if (!lim) lim = &default_lim; lim->features |= BLK_FEAT_IO_STAT | BLK_FEAT_NOWAIT; - if (blk_mq_can_poll(set)) + if (set->nr_maps > HCTX_TYPE_POLL) lim->features |= BLK_FEAT_POLL; q = blk_alloc_queue(lim, set->numa_node); @@ -5024,8 +5018,6 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, fallback: blk_mq_update_queue_map(set); list_for_each_entry(q, &set->tag_list, tag_set_list) { - struct queue_limits lim; - blk_mq_realloc_hw_ctxs(set, q); if (q->nr_hw_queues != set->nr_hw_queues) { @@ -5039,13 +5031,6 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, set->nr_hw_queues = prev_nr_hw_queues; goto fallback; } - lim = queue_limits_start_update(q); - if (blk_mq_can_poll(set)) - lim.features |= BLK_FEAT_POLL; - else - lim.features &= ~BLK_FEAT_POLL; - if (queue_limits_commit_update(q, &lim) < 0) - pr_warn("updating the poll flag failed\n"); blk_mq_map_swqueue(q); } -- 2.45.2