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 us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 F08EEC88CB2 for ; Fri, 25 Aug 2023 02:45:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1692931526; h=from:from:sender: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:list-id:list-help: list-unsubscribe:list-subscribe:list-post; bh=n2uWQEWgWHy7Mf2g0Q7Eceo9+N3kI3C6qoDD3ukqi4A=; b=apHsYQCQDKJiqY91wePClt1M3y/ECHK4GlKSTVnD16zfUlBJpQvHgO+Za7B+LVa1IneRtn FulDeF6qgPImKeQt5HBHgWHys/tsZ2QlbJaj6qPr6pDGjj/+CmIXy8ASj4C7NrBpQ/RiR7 axh/m6gALpYwgsfjDlG2OH1sEPPOImE= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-321-Q6Ne-oXLMOiaYLpEbcV7MQ-1; Thu, 24 Aug 2023 22:45:23 -0400 X-MC-Unique: Q6Ne-oXLMOiaYLpEbcV7MQ-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 960A6803DBE; Fri, 25 Aug 2023 02:45:21 +0000 (UTC) Received: from mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com (mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com [10.30.29.100]) by smtp.corp.redhat.com (Postfix) with ESMTP id 47CF66B2B2; Fri, 25 Aug 2023 02:45:21 +0000 (UTC) Received: from mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com (localhost [IPv6:::1]) by mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com (Postfix) with ESMTP id 2741119465A3; Fri, 25 Aug 2023 02:45:21 +0000 (UTC) Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) by mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com (Postfix) with ESMTP id A90741946589 for ; Fri, 25 Aug 2023 02:45:19 +0000 (UTC) Received: by smtp.corp.redhat.com (Postfix) id 926BC40C6F4E; Fri, 25 Aug 2023 02:45:19 +0000 (UTC) Received: from mimecast-mx02.redhat.com (mimecast10.extmail.prod.ext.rdu2.redhat.com [10.11.55.26]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 8B14F40C6F4C for ; Fri, 25 Aug 2023 02:45:19 +0000 (UTC) Received: from us-smtp-1.mimecast.com (us-smtp-delivery-1.mimecast.com [205.139.110.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 628F11C0897D for ; Fri, 25 Aug 2023 02:45:19 +0000 (UTC) Received: from zeniv.linux.org.uk (zeniv.linux.org.uk [62.89.141.173]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-638-_KRNsSXTN1GzbDZJ4Nk2kw-1; Thu, 24 Aug 2023 22:45:16 -0400 X-MC-Unique: _KRNsSXTN1GzbDZJ4Nk2kw-1 Received: from viro by zeniv.linux.org.uk with local (Exim 4.96 #2 (Red Hat Linux)) id 1qZMoj-000edp-26; Fri, 25 Aug 2023 02:44:57 +0000 Date: Fri, 25 Aug 2023 03:44:57 +0100 From: Al Viro To: Christoph Hellwig Message-ID: <20230825024457.GD95084@ZenIV> References: <20230608110258.189493-1-hch@lst.de> <20230608110258.189493-2-hch@lst.de> MIME-Version: 1.0 In-Reply-To: <20230608110258.189493-2-hch@lst.de> X-Mimecast-Impersonation-Protect: Policy=CLT - Impersonation Protection Definition; Similar Internal Domain=false; Similar Monitored External Domain=false; Custom External Domain=false; Mimecast External Domain=false; Newly Observed Domain=false; Internal User Name=false; Custom Display Name List=false; Reply-to Address Mismatch=false; Targeted Threat Dictionary=false; Mimecast Threat Dictionary=false; Custom Threat Dictionary=false X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 Subject: Re: [dm-devel] [PATCH 01/30] block: also call ->open for incremental partition opens X-BeenThere: dm-devel@redhat.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: device-mapper development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Vignesh Raghavendra , "Rafael J. Wysocki" , linux-nvme@lists.infradead.org, Phillip Potter , Chris Mason , dm-devel@redhat.com, "Md. Haris Iqbal" , Pavel Machek , Miquel Raynal , Jack Wang , linux-nilfs@vger.kernel.org, linux-scsi@vger.kernel.org, Richard Weinberger , linux-pm@vger.kernel.org, linux-um@lists.infradead.org, Josef Bacik , Coly Li , linux-block@vger.kernel.org, linux-bcache@vger.kernel.org, David Sterba , Jens Axboe , Christian Brauner , "Martin K. Petersen" , linux-f2fs-devel@lists.sourceforge.net, linux-fsdevel@vger.kernel.org, linux-mtd@lists.infradead.org, linux-btrfs@vger.kernel.org Errors-To: dm-devel-bounces@redhat.com Sender: "dm-devel" X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: zeniv.linux.org.uk Content-Disposition: inline Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit On Thu, Jun 08, 2023 at 01:02:29PM +0200, Christoph Hellwig wrote: > --- a/block/bdev.c > +++ b/block/bdev.c > @@ -683,9 +683,6 @@ static int blkdev_get_part(struct block_device *part, fmode_t mode) > struct gendisk *disk = part->bd_disk; > int ret; > > - if (atomic_read(&part->bd_openers)) > - goto done; > - > ret = blkdev_get_whole(bdev_whole(part), mode); > if (ret) > return ret; > @@ -694,9 +691,10 @@ static int blkdev_get_part(struct block_device *part, fmode_t mode) > if (!bdev_nr_sectors(part)) > goto out_blkdev_put; > > - disk->open_partitions++; > - set_init_blocksize(part); > -done: > + if (!atomic_read(&part->bd_openers)) { > + disk->open_partitions++; > + set_init_blocksize(part); > + } [with apologies for very late (and tangential) reply] That got me curious about the ->bd_openers - do we need it atomic? Most of the users (and all places that do modifications) are under ->open_mutex; the only exceptions are * early sync logics in blkdev_put(); it's explicitly racy - see the comment there. * callers of disk_openers() in loop and nbd (the ones in zram are under ->open_mutex). There's driver-private exclusion around those, but in any case - READ_ONCE() is no worse than atomic_read() in those cases. Is there something subtle I'm missing here? -- dm-devel mailing list dm-devel@redhat.com https://listman.redhat.com/mailman/listinfo/dm-devel