From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.9]) (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 B51D21B81D3; Thu, 9 Oct 2025 15:15:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.9 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760022905; cv=none; b=Lq9FDf1wNAPaeqEj5sKXus9KOmFx6jr0pwScDV+z3l2Kzj+yvJq+LbegZ9WnajFWV892Udh0orAApNxfFQgMZMbJ4oF1DU46o9Hnjzol9HkPa52wZyaUYizkJSkpfK2cPR57XKl4+qvqTXsbOch++f2uQc3UTrxu4mi/LQEpcR8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760022905; c=relaxed/simple; bh=8j8r/z6+mSAv9jRtQG+nhZw4Ea8UNAt0HcGb1nWfsS8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=pFIkgeu7G/4CgGWyHG8KVnunCRMnxm/+b3od+O/yCt5nt2+BYd0Y8t+/wsdBfKI1V7nrKSk2K4JMw+tBbe3lu4hDj+/7va/1cZk/slK3U/fv2KOMWV3YGJtChpKTJ34PMIvCWiYXbQGbz9XpDGCOtQq8dZkwE+y5ptls06T/n2M= 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=VMWKINTX; arc=none smtp.client-ip=192.198.163.9 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="VMWKINTX" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1760022904; x=1791558904; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=8j8r/z6+mSAv9jRtQG+nhZw4Ea8UNAt0HcGb1nWfsS8=; b=VMWKINTXjbfGVSnQ7JapKqjx/sJQ5EInlL07dFAbh+iJsmj/3VdOphdn dDAVAFGQ8qU1Tl9GMwMEjn6+TYCLNdSNT/sWwSRTYGmfVbGcZLmrOdtCe Zt+mHRj9FGpt+EhlAQ//9qNIIvBh6irpi32s1oWVHOBoGKCP4AFxN65QF wrsFb1j5LB02wjrBgQZMyUf/Cqq4XNb/I0RPJWMzSqa/xofJh42Jp2UoZ 7IRE1R1942y1thhEcP9RiVaLpJ0ahq0isdB47KQBirHF/peNNAk3eqXTT 6JoPb/crfbD9d7oyPuikxL6TRlsL58BSudJCF2hRdZW7VbznNisUI3THy A==; X-CSE-ConnectionGUID: r+bpg4Q+R1+h/o6ygK1O7A== X-CSE-MsgGUID: Z2sjY5z4RFGcx61FcW1pmQ== X-IronPort-AV: E=McAfee;i="6800,10657,11577"; a="72915283" X-IronPort-AV: E=Sophos;i="6.19,216,1754982000"; d="scan'208";a="72915283" Received: from fmviesa004.fm.intel.com ([10.60.135.144]) by fmvoesa103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Oct 2025 08:15:02 -0700 X-CSE-ConnectionGUID: jzZtpRVYQyS7NJEG27gY3A== X-CSE-MsgGUID: vFc4sSeLRhWjzz5bwS2M3Q== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.19,216,1754982000"; d="scan'208";a="186004030" Received: from kcaccard-desk.amr.corp.intel.com (HELO [10.125.111.11]) ([10.125.111.11]) by fmviesa004-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Oct 2025 08:15:01 -0700 Message-ID: <486185f6-7da7-4fdc-9206-8f1eebd341cf@intel.com> Date: Thu, 9 Oct 2025 08:15:00 -0700 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] iomap: move prefaulting out of hot write path To: "Darrick J. Wong" , alexjlzheng@gmail.com, dave.hansen@linux.intel.com Cc: brauner@kernel.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Jinliang Zheng References: <20251009090851.2811395-1-alexjlzheng@tencent.com> <20251009150125.GD6188@frogsfrogsfrogs> 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: <20251009150125.GD6188@frogsfrogsfrogs> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/9/25 08:01, Darrick J. Wong wrote: > On Thu, Oct 09, 2025 at 05:08:51PM +0800, alexjlzheng@gmail.com wrote: >> From: Jinliang Zheng >> >> Prefaulting the write source buffer incurs an extra userspace access >> in the common fast path. Make iomap_write_iter() consistent with >> generic_perform_write(): only touch userspace an extra time when >> copy_folio_from_iter_atomic() has failed to make progress. >> >> This patch is inspired by commit 665575cff098 ("filemap: move >> prefaulting out of hot write path"). > Seems fine to me, but I wonder if dhansen has any thoughts about this > patch ... which exactly mirrors one he sent eight months ago? I don't _really_ care all that much. But, yeah, I would have expected a little shout-out or something when someone copies the changelog and code verbatim from another patch: https://lore.kernel.org/lkml/20250129181753.3927F212@davehans-spike.ostc.intel.com/ and then copies a comment from a second patch I did. But I guess I was cc'd at least. Also, if my name isn't on this one, then I don't have to fix any of the bugs it causes. Right? ;) Just one warning: be on the lookout for bugs in the area. The prefaulting definitely does a good job of hiding bugs in other bits of the code. The generic_perform_write() gunk seems to have uncovered a bug or two. Also, didn't Christoph ask you to make the comments wider the last time Alex posted this? I don't think that got changed. https://lore.kernel.org/lkml/aIt8BYa6Ti6SRh8C@infradead.org/ Overall, the change still seems as valid to me as it did when I wrote the patch in the first place. Although it feels funny to ack my own patch.