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 15A06C433EF for ; Wed, 16 Feb 2022 15:20:31 +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=2BQAQrgnY+ZjEcPbeOm+3aZRepsY8CLjtYSHxUYHEQ0=; b=thUlm9RZnoZT8uqEsxxAGW5/ZT eqdd9tSvwyhXoTa89itKazZaS8SugI7LDawNHJM44+y4iuYcf9FPndkh3FTpzCCX4TERE3KGTRwVp +qT5Ouh97i/pLpHK3PxotpaLWuw0/hj4LxfqkiUj51w6+YquMsEFA8wQ5Jn6meULdLvlupkil7f75 uw1+Rmb6mrf3QncscLZOty6xARosIc97lQ+7AXRXfZ8EpSEVU+kPlCGmg1TUHhirhgqfoypiHXX9L xrX6xNrhhmy7xhPulHtK6fZnbcnFGS7q9xcTLx9/t8xGkGqdB0JcnoltRvm5lrzPsz3WR8akcDgVG /Bd70LNA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nKM6U-007TlA-Ja; Wed, 16 Feb 2022 15:20:26 +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 1nKM6R-007Tk5-Hd for linux-nvme@lists.infradead.org; Wed, 16 Feb 2022 15:20:24 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id D43FE68B05; Wed, 16 Feb 2022 16:20:19 +0100 (CET) Date: Wed, 16 Feb 2022 16:20:19 +0100 From: Christoph Hellwig To: Hannes Reinecke Cc: Christoph Hellwig , axboe@kernel.dk, kbusch@kernel.org, markus.bloechl@ipetronik.com, linux-nvme@lists.infradead.org, linux-block@vger.kernel.org Subject: Re: [PATCH 2/2] block: skip the fsync_bdev call in del_gendisk for surprise removals Message-ID: <20220216152019.GA19002@lst.de> References: <20220216150901.4166235-1-hch@lst.de> <20220216150901.4166235-2-hch@lst.de> <4f29d9a3-021c-f2f0-b452-e682fa1db459@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4f29d9a3-021c-f2f0-b452-e682fa1db459@suse.de> 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-20220216_072023_758476_6C6DCB01 X-CRM114-Status: GOOD ( 13.06 ) 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 Wed, Feb 16, 2022 at 04:18:43PM +0100, Hannes Reinecke wrote: > My turn to be picky: > In the previous patch you use 'set_bit()' for GD_DEAD, which to my > knowledge doesn't imply a memory barrier. > Yet here you rely on that for the 'test_bit()' to return the correct/most > recent value. > Don't we need a memory barrier here somewhere? Well, we only do the test to skip useless work. A race is not a problem here.