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 12DDDC25B75 for ; Thu, 23 May 2024 12:40:05 +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=HqZOfmor5NqVcKizrVNquDxO3/cE7Duj6ik/S3nYDoQ=; b=WJnsz3QBcG4bgAzplhPeGlQJ1L kNQL15dYY1UTRCTDuQcIwLmGk3Lcu0cxpaTjC36LSvZ2utbwFvr89PEHRN3zOTDcJrb3y3Ue5fFI3 P7Oq4Q3Kk2+gCOaawK5iQy2VagiK6WxFR2/KDU9PFmQkb0B8LrDgLGd5oklwVv5jp+MsXRSXF9SV5 9JxGuGB5qr3pY5S3pnh20f+ALBWRbFKWlxrib2+mxjn+Yb/Ub/JdO9l72GpvbKuuPWUoNxcHdhU3l d4r2q4W2L7SfjM71Cvk3xpSmErVTqyjUq2B7/akUL0tE1n+ARvenPZkAb/1rwdMgxnnOQeGXmWgcl wer5guXg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sA7jj-00000006DHT-1qy6; Thu, 23 May 2024 12:39:59 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1sA7jg-00000006DGp-0xnp for linux-nvme@lists.infradead.org; Thu, 23 May 2024 12:39:57 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id 3A91868BFE; Thu, 23 May 2024 14:39:50 +0200 (CEST) Date: Thu, 23 May 2024 14:39:49 +0200 From: Christoph Hellwig To: Sagi Grimberg Cc: Christoph Hellwig , Keith Busch , Shinichiro Kawasaki , "linux-nvme@lists.infradead.org" Subject: Re: [PATCH] nvme-pci: silence a lockdep complaint Message-ID: <20240523123949.GA20758@lst.de> References: <20240522091534.472449-1-sagi@grimberg.me> <20240522162845.GA16783@lst.de> <20240523065412.GA29137@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-20240523_053956_432484_D9C144B7 X-CRM114-Status: GOOD ( 16.11 ) 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, May 23, 2024 at 01:04:13PM +0300, Sagi Grimberg wrote: > > > On 23/05/2024 9:54, Christoph Hellwig wrote: >> On Wed, May 22, 2024 at 03:36:19PM -0600, Keith Busch wrote: >>> The below patch is what I'm messing with. I have a CMIC PCI NVMe and >>> nvme native multipathing enabled, and that can recreate the lockdep >>> splat 100% of the time. It goes away with this patch. Non-multipath >>> devices are harder to hit the lockdep splat for a different reason. >> I much prefer the srcu locking as it has real benefits as well over >> a global-ish rwsem. I'll try to get to a real review in a bit. >> > > Can you explain what are these benefits? No having a global lock taken for namespace lookups.