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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id A1F28C3DA4A for ; Thu, 22 Aug 2024 20:45:42 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 16B7280062; Thu, 22 Aug 2024 16:45:42 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 11C978005A; Thu, 22 Aug 2024 16:45:42 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id ED6C380062; Thu, 22 Aug 2024 16:45:41 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id CF0678005A for ; Thu, 22 Aug 2024 16:45:41 -0400 (EDT) Received: from smtpin23.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 5675841A2B for ; Thu, 22 Aug 2024 20:45:41 +0000 (UTC) X-FDA: 82481062482.23.27CB868 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf27.hostedemail.com (Postfix) with ESMTP id 8C6CA40018 for ; Thu, 22 Aug 2024 20:45:39 +0000 (UTC) Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=HWUKh0j4; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf27.hostedemail.com: domain of broonie@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=broonie@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1724359522; a=rsa-sha256; cv=none; b=A3rYQx6FVsxxU/i0STlSlcCEuqvbe+oWalCvdjz3OEEYbMCtiX3vmNNhjENtg2HoILpI98 KcNOQJMroCn9Q916noVMIMJyy9X2nTE32Bdipsir76lNg+Nj5DtRreDnm9uTFT7CXmcLpN 2XV1+aLw3m9BfKeWMHzvP4ERtDI3WPo= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=HWUKh0j4; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf27.hostedemail.com: domain of broonie@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=broonie@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1724359522; h=from:from: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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=eOcdGuPfwwIMkDW9F1JPEpI+IcEDmPAwd0C63Wwu1OE=; b=GhfEpPNo43wBIgJJECVJiKF5a42J4oOfCAiM6yFufw1Dhn/QeVPRAUCnCHxk+JCuJjmM/H xutxIImdxzq3pl8KGzYiGs5Ese5MM+8qiO+7uPU271nf0a+t77EucgyvM98Sy+riNzUfad i60ucNXW64JMFjz97sZf6wlChB35bhA= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id 94D9861228; Thu, 22 Aug 2024 20:45:38 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D10DFC32782; Thu, 22 Aug 2024 20:45:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1724359538; bh=XWJGcW0yVcEmLEupBHIYRHIv6dBL2UB76q3jGJxsu4E=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=HWUKh0j4Cnsa8UbbM0rYlW6UaYrDnlnMMy5ONE/G/1I8lZs6rqAJKAY7tGZGco2sn Zsfn+vxVAbYQky8PrH5ItBXkW84tn9atEv7OIT7jB6RziMjk+J1rS1+ZfsEhkZbq5K hhwdZVTah3kZnzUH9t6/QbR3C5HI184vmhXU9DPhLEaL2U+ofNy4PTX8n/5v3cT/mw 10bPorKmYobSnJbbikHHdHrvr1xozjGqkFBvNFIraF9YaMvJJKupLu39L8SbB4p5aw Noy89LDpzhw6Cm2H/8heFfa6c+OPEwDtL0k0LOefHp+O40gxTKDiUIx2JuZYUP6s6u qy24raiK6Ak8Q== Date: Thu, 22 Aug 2024 21:45:35 +0100 From: Mark Brown To: Matthew Wilcox Cc: "Liam R. Howlett" , Cristian Ciocaltea , maple-tree@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/5] maple_tree: Allow external locks to be configured with their map Message-ID: References: <20240822-b4-regmap-maple-nolock-v1-0-d5e6dbae3396@kernel.org> <20240822-b4-regmap-maple-nolock-v1-1-d5e6dbae3396@kernel.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="eY41iKqCdtWMhFlH" Content-Disposition: inline In-Reply-To: X-Cookie: Your love life will be... interesting. X-Rspam-User: X-Rspamd-Queue-Id: 8C6CA40018 X-Rspamd-Server: rspam01 X-Stat-Signature: ubs5hz6f8fxmaqxohf43q7538jbu7dfs X-HE-Tag: 1724359539-18518 X-HE-Meta: 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 /7o6UIuX 1gfBX2AIO+/RkMD/uSdiLxbzMwytkWgL/VUgHB37fdhhlbOumF4Uoxp1KlNhE5USf5l07O855wDVrYuOoQib/g0PWsaqhCWHZM4KHjhDKTdyXykyHevTWPr+fJLM+nQTdMpT7IbRIQesavv8q7gnA3Z8Xzk4tqqVBAHLDfU1M9SRQDlnNGkoq0PUoTSSsJwhSl2h+IH+G7T3QntbKvsdpd6wVk2O4hwaBMiOKqoAABQ7Kq5BpAi+7lTg26PESGjUMvLa7SphofyUA9Y4b1kqKO+NjwDtokpnpPbBD3mwjjyjQ2/5oyURB9z1bLE/kOdgXlkQMGa5Q2IwXgSu63oKHm/S317Ac541ReokSszouWatrs6E= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000029, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: --eY41iKqCdtWMhFlH Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Thu, Aug 22, 2024 at 08:55:20PM +0100, Matthew Wilcox wrote: > On Thu, Aug 22, 2024 at 08:48:56PM +0100, Mark Brown wrote: > > I mean, we do use the internal lock here since otherwise lockdep moans > > but it's pure overhead which just complicates the code. It's only ever > When it's an uncontended spinlock, there's really no overhead. I wish I'd > been firmer on that point earlier and prohibited the external lock hack. > The point is that the lock protects the tree. If we are ever going to > be able to defragment slabs (and I believe this is an ability that Linux > must gain), we must be able to go from the object (the maple node) to > a lock that will let us reallocate the node. If there's some external > lock that protects the tree, we can't possibly do that. If the external lock guarantees that nothing can possibly be contending access to the tree (including the read side) I don't see any issue there? --eY41iKqCdtWMhFlH Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAmbHo2UACgkQJNaLcl1U h9BYKQf/fju1QFL7eew4kcIkh7VOofjEAnrdmk+guHPAJJekLZH5oIqXpak7g+u+ 9evsL/NIqhR6tZQ7iJSUBnJf2hyriOAmHDzyD0X+ficeQhHGB7d+8ASkq53bUmWz PhVVxFYFJ5bk2DG9kpcHvOdh1wxEk8VHGv8EalkVapEbQuuYwH/ZnJ/x0GyuJ0EO SoE7mcgjkrxDl6QpJDTOAIu5UWgjfa/R77LgcT7jCaOXmsn8LR6Kx8VTC/6z1TDz 61qmV+XcvHMSJ4O4hLm5fVFQkBP6fEPl7V8rVKmT5ebV8XmNyNg1NsjhbMYpjtki GfONtM47Oz++f4QHafeNdUxjtV+GBg== =ZFM8 -----END PGP SIGNATURE----- --eY41iKqCdtWMhFlH--