From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.15]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E93A034DCC8; Thu, 11 Jun 2026 21:04:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.15 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781211848; cv=none; b=sXsuYLjGxKnyoJe3BSCeywv2APn8tV0dpEBfqtotJ3F6Cssh4WfeZNUoRRB5kX0kPLZquELFcqFImXT6rOQPX/FS95doq2nsO+vrD0Bnf4j4URsHgHdGMO4n2qpXb0b1xEkWHz04C+3DANXijk3wK8cFbI0aVYxMZYgCTc33VKM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781211848; c=relaxed/simple; bh=XDSUbCO16VkgZo3LublOvVmpMgadl7ko2l2nSpzc4+U=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=EJiMCaGMWcTdSvTG+AkPU9BZIdUnKn0SKfu7B+fUdD242qWe5I4duBny0uZUf5LPIisg0jFQALWM+gP9eYfJMnWT/2UPoqMHaJ7afDxLPQX0Ji/7gA+22AEgArASb2ZZkb8AFiZveg/l0jNhzXVIlC3jNezVOc8YqigPKCJhyrk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=KYSVKpam; arc=none smtp.client-ip=192.198.163.15 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="KYSVKpam" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1781211847; x=1812747847; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=XDSUbCO16VkgZo3LublOvVmpMgadl7ko2l2nSpzc4+U=; b=KYSVKpamPzOWENDIK2Ik368+P2rh8Iir6B98VPuzsF/awoP6COBLFv4G Ji1lpxEDIgYyYHmT/H4mg8QenHUNUF4Rzeqa0btf1hB1GimwWDb40oWXz lXeCq//yVxNkZh3g2Gv3idoBPkWOq84I/RHtRGDOp6vNGRgjs6bu8qN4e am5ZJBGJitsUgWsPcJyYuUKfZLav2ndZqtm1kJe/U7ySLj9k2rQlb2ZTc 90+oJh4Kz79PFQxlC1hiz4Zpq/yS+IxHOz+kGYoa2N3zMSRozb3jKlvND M+7nGgergKgqIyS1k4B7QnoYwdW100+KkkqHJhyN7vfKYR7lv+IDzNWI9 w==; X-CSE-ConnectionGUID: J8Z+S59gTB+2x6LMbjKqkA== X-CSE-MsgGUID: mLSV4oklQ7+JPXLiOYAxqw== X-IronPort-AV: E=McAfee;i="6800,10657,11813"; a="82146891" X-IronPort-AV: E=Sophos;i="6.24,199,1774335600"; d="scan'208";a="82146891" Received: from fmviesa007.fm.intel.com ([10.60.135.147]) by fmvoesa109.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Jun 2026 14:04:06 -0700 X-CSE-ConnectionGUID: OZ2+virnQjSJjOUxUevWbQ== X-CSE-MsgGUID: WObkYNGrTeOIkFy3Ag84xQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.24,199,1774335600"; d="scan'208";a="243673202" Received: from rfrazer-mobl3.amr.corp.intel.com (HELO [10.125.110.112]) ([10.125.110.112]) by fmviesa007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Jun 2026 14:04:06 -0700 Message-ID: <8ed21cfe-5114-4002-a53c-af43f337d2aa@intel.com> Date: Thu, 11 Jun 2026 14:04:04 -0700 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 3/5] mm: Add RCU-based VMA lookup helper that waits for writers To: Suren Baghdasaryan , Dave Hansen Cc: linux-kernel@vger.kernel.org, Alice Ryhl , Andrew Morton , =?UTF-8?B?QXJ2ZSBIasO4bm5ldsOl?= =?UTF-8?Q?g?= , Carlos Llamas , Christian Brauner , David Ahern , "David S. Miller" , Greg Kroah-Hartman , "Liam R. Howlett" , linux-mm@kvack.org, Lorenzo Stoakes , netdev@vger.kernel.org, Shakeel Butt , Todd Kjos , Vlastimil Babka References: <20260610230409.A44D29FA@davehans-spike.ostc.intel.com> <20260610230415.C0521C88@davehans-spike.ostc.intel.com> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; keydata= xsFNBE6HMP0BEADIMA3XYkQfF3dwHlj58Yjsc4E5y5G67cfbt8dvaUq2fx1lR0K9h1bOI6fC oAiUXvGAOxPDsB/P6UEOISPpLl5IuYsSwAeZGkdQ5g6m1xq7AlDJQZddhr/1DC/nMVa/2BoY 2UnKuZuSBu7lgOE193+7Uks3416N2hTkyKUSNkduyoZ9F5twiBhxPJwPtn/wnch6n5RsoXsb ygOEDxLEsSk/7eyFycjE+btUtAWZtx+HseyaGfqkZK0Z9bT1lsaHecmB203xShwCPT49Blxz VOab8668QpaEOdLGhtvrVYVK7x4skyT3nGWcgDCl5/Vp3TWA4K+IofwvXzX2ON/Mj7aQwf5W iC+3nWC7q0uxKwwsddJ0Nu+dpA/UORQWa1NiAftEoSpk5+nUUi0WE+5DRm0H+TXKBWMGNCFn c6+EKg5zQaa8KqymHcOrSXNPmzJuXvDQ8uj2J8XuzCZfK4uy1+YdIr0yyEMI7mdh4KX50LO1 pmowEqDh7dLShTOif/7UtQYrzYq9cPnjU2ZW4qd5Qz2joSGTG9eCXLz5PRe5SqHxv6ljk8mb ApNuY7bOXO/A7T2j5RwXIlcmssqIjBcxsRRoIbpCwWWGjkYjzYCjgsNFL6rt4OL11OUF37wL QcTl7fbCGv53KfKPdYD5hcbguLKi/aCccJK18ZwNjFhqr4MliQARAQABzUVEYXZpZCBDaHJp c3RvcGhlciBIYW5zZW4gKEludGVsIFdvcmsgQWRkcmVzcykgPGRhdmUuaGFuc2VuQGludGVs LmNvbT7CwXgEEwECACIFAlQ+9J0CGwMGCwkIBwMCBhUIAgkKCwQWAgMBAh4BAheAAAoJEGg1 lTBwyZKwLZUP/0dnbhDc229u2u6WtK1s1cSd9WsflGXGagkR6liJ4um3XCfYWDHvIdkHYC1t MNcVHFBwmQkawxsYvgO8kXT3SaFZe4ISfB4K4CL2qp4JO+nJdlFUbZI7cz/Td9z8nHjMcWYF IQuTsWOLs/LBMTs+ANumibtw6UkiGVD3dfHJAOPNApjVr+M0P/lVmTeP8w0uVcd2syiaU5jB aht9CYATn+ytFGWZnBEEQFnqcibIaOrmoBLu2b3fKJEd8Jp7NHDSIdrvrMjYynmc6sZKUqH2 I1qOevaa8jUg7wlLJAWGfIqnu85kkqrVOkbNbk4TPub7VOqA6qG5GCNEIv6ZY7HLYd/vAkVY E8Plzq/NwLAuOWxvGrOl7OPuwVeR4hBDfcrNb990MFPpjGgACzAZyjdmYoMu8j3/MAEW4P0z F5+EYJAOZ+z212y1pchNNauehORXgjrNKsZwxwKpPY9qb84E3O9KYpwfATsqOoQ6tTgr+1BR CCwP712H+E9U5HJ0iibN/CDZFVPL1bRerHziuwuQuvE0qWg0+0SChFe9oq0KAwEkVs6ZDMB2 P16MieEEQ6StQRlvy2YBv80L1TMl3T90Bo1UUn6ARXEpcbFE0/aORH/jEXcRteb+vuik5UGY 5TsyLYdPur3TXm7XDBdmmyQVJjnJKYK9AQxj95KlXLVO38lczsFNBFRjzmoBEACyAxbvUEhd GDGNg0JhDdezyTdN8C9BFsdxyTLnSH31NRiyp1QtuxvcqGZjb2trDVuCbIzRrgMZLVgo3upr MIOx1CXEgmn23Zhh0EpdVHM8IKx9Z7V0r+rrpRWFE8/wQZngKYVi49PGoZj50ZEifEJ5qn/H Nsp2+Y+bTUjDdgWMATg9DiFMyv8fvoqgNsNyrrZTnSgoLzdxr89FGHZCoSoAK8gfgFHuO54B lI8QOfPDG9WDPJ66HCodjTlBEr/Cwq6GruxS5i2Y33YVqxvFvDa1tUtl+iJ2SWKS9kCai2DR 3BwVONJEYSDQaven/EHMlY1q8Vln3lGPsS11vSUK3QcNJjmrgYxH5KsVsf6PNRj9mp8Z1kIG qjRx08+nnyStWC0gZH6NrYyS9rpqH3j+hA2WcI7De51L4Rv9pFwzp161mvtc6eC/GxaiUGuH BNAVP0PY0fqvIC68p3rLIAW3f97uv4ce2RSQ7LbsPsimOeCo/5vgS6YQsj83E+AipPr09Caj 0hloj+hFoqiticNpmsxdWKoOsV0PftcQvBCCYuhKbZV9s5hjt9qn8CE86A5g5KqDf83Fxqm/ vXKgHNFHE5zgXGZnrmaf6resQzbvJHO0Fb0CcIohzrpPaL3YepcLDoCCgElGMGQjdCcSQ+Ci FCRl0Bvyj1YZUql+ZkptgGjikQARAQABwsFfBBgBAgAJBQJUY85qAhsMAAoJEGg1lTBwyZKw l4IQAIKHs/9po4spZDFyfDjunimEhVHqlUt7ggR1Hsl/tkvTSze8pI1P6dGp2XW6AnH1iayn yRcoyT0ZJ+Zmm4xAH1zqKjWplzqdb/dO28qk0bPso8+1oPO8oDhLm1+tY+cOvufXkBTm+whm +AyNTjaCRt6aSMnA/QHVGSJ8grrTJCoACVNhnXg/R0g90g8iV8Q+IBZyDkG0tBThaDdw1B2l asInUTeb9EiVfL/Zjdg5VWiF9LL7iS+9hTeVdR09vThQ/DhVbCNxVk+DtyBHsjOKifrVsYep WpRGBIAu3bK8eXtyvrw1igWTNs2wazJ71+0z2jMzbclKAyRHKU9JdN6Hkkgr2nPb561yjcB8 sIq1pFXKyO+nKy6SZYxOvHxCcjk2fkw6UmPU6/j/nQlj2lfOAgNVKuDLothIxzi8pndB8Jju KktE5HJqUUMXePkAYIxEQ0mMc8Po7tuXdejgPMwgP7x65xtfEqI0RuzbUioFltsp1jUaRwQZ MTsCeQDdjpgHsj+P2ZDeEKCbma4m6Ez/YWs4+zDm1X8uZDkZcfQlD9NldbKDJEXLIjYWo1PH hYepSffIWPyvBMBTW2W5FRjJ4vLRrJSUoEfJuPQ3vW9Y73foyo/qFoURHO48AinGPZ7PC7TF vUaNOTjKedrqHkaOcqB185ahG2had0xnFsDPlx5y In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/11/26 13:35, Suren Baghdasaryan wrote: >> + /* Slow path: preclude VMA writers by getting mmap read lock. */ >> + guard(rwsem_read)(&mm->mmap_lock); > guard() is nice but mmap_read_{lock|unlock} has those > __mmap_lock_trace_* traces which we lose with guard(). Not sure if > that's a good enough reason to keep using older primitives. I stole the guard() from Lorenzo's suggestion. I'm totally fine doing it whichever way you two would prefer. I'm old school but I personally find guard() harder to read. I tend to only use it where it is *vastly* superior to explicit lock/unlock. But, seriously, I'm open to whatever folks want.