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 EF65CC433F5 for ; Fri, 8 Apr 2022 05:46:53 +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:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=/rJXrqGxCxJ1EcVkkpsdq1B87jM7PqoRPPeklMr5l8A=; b=oj2Iz9B0PvylaxRrhEtuPrILGT dkzqAxkaCZyMZhCZM5zJTN9I2nUC2olCPlOvZNcXsu+S3QO3NFj9KozaWjH63TihfCh3tUEJwBpEb hmq5ty6vIivuWjjUEdAe9JzlkyuIuEDt3TRaHQ5bsw9//uCU4M4pkAE7pXLbkDt59LrD2MNMOprAV KIngxF0BUflejmBANJmN1mGcY/y+DoC7shDY5H1tS2Se7Vk8KzHU62MGz0XIx6c13XTaudsoOBZ0M XQtQZ0xNYcgrKe1J2tQ0ubugU7rk1mCbb8tw/hmXKRlrKNBX4B/vHjzMnG9+fV1Myzppc10fE3LNc W/pSdLNA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nchSN-00FC1w-86; Fri, 08 Apr 2022 05:46:51 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nchSJ-00FC1A-Tm for linux-nvme@lists.infradead.org; Fri, 08 Apr 2022 05:46:49 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id 3983668AFE; Fri, 8 Apr 2022 07:46:45 +0200 (CEST) Date: Fri, 8 Apr 2022 07:46:44 +0200 From: Christoph Hellwig To: Hannes Reinecke Cc: Christoph Hellwig , Sagi Grimberg , Keith Busch , linux-nvme@lists.infradead.org Subject: Re: [PATCH 1/3] nvmet: make the subsystem type configurable Message-ID: <20220408054644.GC32232@lst.de> References: <20220407104808.29007-1-hare@suse.de> <20220407104808.29007-2-hare@suse.de> <20220407154417.GC15988@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220407_224648_172883_B3D74879 X-CRM114-Status: GOOD ( 14.64 ) 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 On Thu, Apr 07, 2022 at 06:55:09PM +0200, Hannes Reinecke wrote: >>> + down_read(&nvmet_config_sem); >>> + list_for_each_entry(p, &nvmet_ports_list, global_entry) { >>> + list_for_each_entry(s, &p->subsystems, entry) { >>> + if (s->subsys == subsys) { >>> + up_read(&nvmet_config_sem); >>> + return -EACCES; >>> + } >>> + } >>> + } >>> + up_read(&nvmet_config_sem); >> >> Does this scale? Do we want a flag in the subsystem instead? >> > Hmm. Seeing that it's a synchronous userspace operation I don't really > care; worst case the 'ln -s' call takes a bit longer. > But okay, I'll have a look. Well, it is quadratic behavior, wich we generally avoid. Something like a counter of enabled ports in the subsystem should easily remove the need for it.