From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mout.gmx.net (mout.gmx.net [212.227.15.19]) (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 389CC1A9FA8 for ; Mon, 8 Dec 2025 20:26:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=212.227.15.19 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765225615; cv=none; b=jfB4ttTTgA0n6Ciowt1CwkeJGHdCW/FuOe8Q6B/of1OhHTL6zAcLcgwScwVfdGrIAnpwwiVWckwJWCXJZ1gj9H0UaXLNfxBLNHIWNx1bzd4dmfq6tF8ZlvwxUQBaPzmWjCVTczSJCjKCAM/KwJX137HCs9cVV7U/IpZq8NWMonE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765225615; c=relaxed/simple; bh=unowFCT+S+eege1c3CX0C5EXxO7A803osv/bp1mReJw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=eTf3O52+tr79et72XB6uXOP/5aabFjstQ8HPMCAzj5B7Dg6ssiP3HbppdKHKHrSiBo2JEbDm0eZBDL/+pkvmYHVjoa9+SUyHMCM2DIeB2BnVckHRZW0RID/8ReQGzTmO8XuCdyvrz2UHB0u46+TX25vPmcbXM1QvbCNOtpSnmes= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=gmx.com; spf=pass smtp.mailfrom=gmx.com; dkim=pass (2048-bit key) header.d=gmx.com header.i=quwenruo.btrfs@gmx.com header.b=MUtZNRzl; arc=none smtp.client-ip=212.227.15.19 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=gmx.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmx.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmx.com header.i=quwenruo.btrfs@gmx.com header.b="MUtZNRzl" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmx.com; s=s31663417; t=1765225610; x=1765830410; i=quwenruo.btrfs@gmx.com; bh=eU7HqGYI4N9/xIH0VAxPMMvuP7yug9KsVkYnylS5tM0=; h=X-UI-Sender-Class:Message-ID:Date:MIME-Version:Subject:To:Cc: References:From:In-Reply-To:Content-Type: Content-Transfer-Encoding:cc:content-transfer-encoding: content-type:date:from:message-id:mime-version:reply-to:subject: to; b=MUtZNRzly+cSQYAo1nyXV8dey9G5AjLLP8m88GFLD6aF6cNbnl84R4f+OUxFl5K9 sEjHMdjyKqlRLEAJKcsceIA21tBXJXy/aA3eMrLrdHIWcnTIJEfrzF1Kf91vUjIb0 lTfAlxi1nvjvbhPcDMHh1LTevoOLhqJKw9Cr0SBp0parOjBRjf65l1OL75dyvTT7M UfjX6/64VqeLe9rejl0XZWs28020x79OafpIeiMtfof9Jvku7UKLZZKhPsmojr8OW CYKeT4Pq7k4HkiSIM+TROr60F1bzpzGIFtFq5to6nqtCd7Eo4x1+3xyujLdNiEVUF 7PXwpBTOn0mseFcGVw== X-UI-Sender-Class: 724b4f7f-cbec-4199-ad4e-598c01a50d3a Received: from [172.16.0.229] ([159.196.52.54]) by mail.gmx.net (mrgmx004 [212.227.17.184]) with ESMTPSA (Nemesis) id 1MbAcs-1w4FUY1BE0-00jXak; Mon, 08 Dec 2025 21:26:50 +0100 Message-ID: <3bbfc8bc-0b15-461b-90a4-a59d2b7fd97e@gmx.com> Date: Tue, 9 Dec 2025 06:56:47 +1030 Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] btrfs: shrink the size of btrfs_bio To: dsterba@suse.cz, Qu Wenruo Cc: linux-btrfs@vger.kernel.org References: <7ef5de8f907f74520338f0ce46f36f1335dc6e2f.1764921800.git.wqu@suse.com> <20251208191903.GA4859@twin.jikos.cz> Content-Language: en-US From: Qu Wenruo Autocrypt: addr=quwenruo.btrfs@gmx.com; keydata= xsBNBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAHNIlF1IFdlbnJ1byA8cXV3ZW5ydW8uYnRyZnNAZ214LmNvbT7CwJQEEwEIAD4CGwMFCwkI BwIGFQgJCgsCBBYCAwECHgECF4AWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCZxF1YAUJEP5a sQAKCRDCPZHzoSX+qF+mB/9gXu9C3BV0omDZBDWevJHxpWpOwQ8DxZEbk9b9LcrQlWdhFhyn xi+l5lRziV9ZGyYXp7N35a9t7GQJndMCFUWYoEa+1NCuxDs6bslfrCaGEGG/+wd6oIPb85xo naxnQ+SQtYLUFbU77WkUPaaIU8hH2BAfn9ZSDX9lIxheQE8ZYGGmo4wYpnN7/hSXALD7+oun tZljjGNT1o+/B8WVZtw/YZuCuHgZeaFdhcV2jsz7+iGb+LsqzHuznrXqbyUQgQT9kn8ZYFNW 7tf+LNxXuwedzRag4fxtR+5GVvJ41Oh/eygp8VqiMAtnFYaSlb9sjia1Mh+m+OBFeuXjgGlG VvQFzsBNBFnVga8BCACqU+th4Esy/c8BnvliFAjAfpzhI1wH76FD1MJPmAhA3DnX5JDORcga CbPEwhLj1xlwTgpeT+QfDmGJ5B5BlrrQFZVE1fChEjiJvyiSAO4yQPkrPVYTI7Xj34FnscPj /IrRUUka68MlHxPtFnAHr25VIuOS41lmYKYNwPNLRz9Ik6DmeTG3WJO2BQRNvXA0pXrJH1fN GSsRb+pKEKHKtL1803x71zQxCwLh+zLP1iXHVM5j8gX9zqupigQR/Cel2XPS44zWcDW8r7B0 q1eW4Jrv0x19p4P923voqn+joIAostyNTUjCeSrUdKth9jcdlam9X2DziA/DHDFfS5eq4fEv ABEBAAHCwHwEGAEIACYCGwwWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCZxF1gQUJEP5a0gAK CRDCPZHzoSX+qHGpB/kB8A7M7KGL5qzat+jBRoLwB0Y3Zax0QWuANVdZM3eJDlKJKJ4HKzjo B2Pcn4JXL2apSan2uJftaMbNQbwotvabLXkE7cPpnppnBq7iovmBw++/d8zQjLQLWInQ5kNq Vmi36kmq8o5c0f97QVjMryHlmSlEZ2Wwc1kURAe4lsRG2dNeAd4CAqmTw0cMIrR6R/Dpt3ma +8oGXJOmwWuDFKNV4G2XLKcghqrtcRf2zAGNogg3KulCykHHripG3kPKsb7fYVcSQtlt5R6v HZStaZBzw4PcDiaAF3pPDBd+0fIKS6BlpeNRSFG94RYrt84Qw77JWDOAZsyNfEIEE0J6LSR/ In-Reply-To: <20251208191903.GA4859@twin.jikos.cz> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:vfm4NB9e3Nl3wwoMNnmM7Cbgf5YfL+MUwkTTFdeP+/WnYpyEU3P Im+EC82aFJi0H32V76HUdJr37YsKP1bxl8azMPcDFMsF6LvboYEYgzvhPAblcIRTtErzmSn ZY/rb5O0VabIVXy11J8zKkKnSBkVqF2DJ3seOGTn2sQOm1lMNCwW665WO7ldEQpqInUcBVL I1XTiQaTsnTkSNyfV0A1Q== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:BSDjClYf3aw=;izJus8jG2iHABxO2SZ07uORiFIX D2jDyyQ6SPoBLW1XDf/7Zb2ChSCyqlk+RxRqPmR3vgtgCB49ucfeCc0noYtlHgM8QZGBLt/AS m9PKQdXubNoac2ywOnM1F1h3cKpO/Jh0vCjDKQ+lIw44qoHcvlaVv+JI1ilflz9wWK/UwQEcL I82qv9b1X6WLakJvFDVf2jO0mfve6ghCZDh+m33B7kAuuubX1a/OOeGWPXPV1Dao9FhKe8PvT D/pfSXoh/RpT0MMGmqprPl1OdY3p0E02tWJ5VJOhAz9dGEUNrBRQ1z6M8AHzdi2hm9WKLD0BM 69C9AZKGfdv/OrcWWveEjGH/pUqTFUYsay0AY2RszAOwNQ0xSpq2Ckf9eNp/77wYLb0ZrP630 proRiwoUaR/quoAPzkNMBKkJPKmxAJ4Tt9O1kiWsGLvCswHrBz/gkfzMLhLoD/XnPiU+rBvjN WmnHhlH2TG0yCoUq3TcejPXyAVgoX0SAQL7KQQ4b4Y4An6YYHskmKuIwRzPphRntECuV8rWjb hlMaC1ItMZWN8WxN/g1GnSEQTf6/kUSoFnRBywiWyrzBouwddjIEcWsowiUGC62drtbr345mD QS0wz09hsN8CUuNoFzcowkjcJzjumVFcdGwDfjlucEBRKwiHF/06oE/rZmhBvNtIpyfS7mvk3 mUYzaPIxUaqyOOtLLMb3mQq9KPfVP7Rr6loyGCQoCqzp3f5vv1ISPHvUh03LOe04jyR6gbQv6 so6I/KHEIGI5X0gtexhw/GR112Wfo6EMRs6L1H+eLUd3xydPq3xVZmatgwbIe07xL5+NRY6Ua Em5yqJU2Qn12S8FBN9dF53CVMO2v/jMkq29BkHFIkx6jLhCZVySRmuYaLGigwF3bn30Et1IIm fFy5/lbjQHBA8YddiNQ9hYFTlGWGidnd7kOPdQE9id+Aj+TGNrXHie/y1Y2CLL/MEqe0m2d8q KOp9xnxNigyaxuf3p20zZKR2fvrByS10cWCtH/BNOIR88pbvq/9FCry6l3HXy75HBtfdnJS4r 7mrUGIyW2HEp30Rbox9Kn1efVGaLT36Bu6D6mSGFclJ8zEj1NoHVHG2uE8uyJ3i1YHJU6fZc3 dhLpx3eDOSodIj9SCerGivOVWTY+m4Nwjpg3vtgu7qLo02m4uDQA4KRiQQ2/AZVEZnV122KmI p2UKnyXq5RnCDrywqPBrjbG/37G2KlvoS8BL18ME2tSzjaYJ7wFlJ9NH6YI9pXuuF/dMJSiTA b3DCixVYuV43pyM27lmlJ1wgQyveXR9OuXdKDiciBqnCxljLwFdfiRqbfcGJoLgWg0WirP06f hB5IDkHUdUw3Rvm8HiP084iSoIN5jTTZopcy9lLcQqTD12ne8s1d0TjFY0mbEnv3jMZho6q2f V9VZ0crYI/z46JSi8jFMaU6Bs7Gpf6a9dElm1mZJH9tYLFnmo0ewta1niNewnOI2JzYG9TlWj nlld7oy5hqipXT6SERPqyaeu8VGY9FY3MxeEkq4oShdJoRl+RAORKeli5bhhKrVBngDeF3xSy y0PpNwgDjk4IVjCfuOwo86V1gad2yiQlHfxdYD7L8scvcnrskvk+DPPsCIAl33llOYPIViicU +eu037/doaXIDknKY7/K6GZ9VafTcsSTOYqw98cp/2NUJDzHSgxLboFLhqYfkzNErhtJSa59p +S1xEkWvlrtc5jKKYgZjxV2NbD3+0xoqlZw/8iyd1Mx8AAtJ4+YkT8Seq7Y49qVgyxVVDjplM 6xv8Mx3M8xTbKR+RT1vhIGQlPDCA2zy1BOu1NHQfyV4KgMYuw3oemU19fzfP5dxaOdmWHlMhV kFZ0pctYGfyaw8RaBOcKAGZGBmoK+uPraLHRXaU8omCZ6eNecmj1TmqUhSvvBbKSOrgrVDp0B OdG/MwIvK2OjIz8SfWE5Gz433zPY8z6oGUDfox9tCOpjiNAIZZ46yBD8eBQtovIz5MFeA68yx FlNOM6At6cktBBd6wT6E6rTDbVcOYxttZl6+qeebQ8CS84TQQZEFQSTbNJm0sv8IMK4iJJHRS Lto/rMJfadlaB1USAQqUyUuodDmg/HkJ+Uoxg4xXFLACR7xJ0v7Ohl6tUeSYRLfRFCTFIAUl6 QRhjVN7wqrVvR0zH7YVYjKsnmMqg7lXff8w4/eOlcFbf6BmeiSQcDF7WoFLLMkiVJnFyu59dO 8qv7WMx5qm5wTvcyauTJRepikFawO41Eah6c6quBWjB8XMoIBrbIrLaiDBBBpLKxhkgI9wriD Apa9W0myRzc8bx8Ou8yPuDUXgQvyNX//3tKOV0rmUtfazB0DKAVU28wItuQCY6CVHKXP87zyh Ygm76xXJck2di0slp9B5+DG0y9lGz8ytveu40FVHcrX8Nnr1fcJdibLpG+/PLXEv9GBIX7D/t o8kpE5lAj9kx/PuNM15D7WOKF3usdxcw5HpiX0mbM15Ik06yaV/Kr57Y2k2Sf7UZzlTairn9M V0xotbMqvbZh85nq1T6VwLxD4hAbhl/1lhcHsbT8Nad5rExzdhsW48fPcGaUqmcNoyIdCin/S q1GUvfLOBxBGoVX+WyoX7VgUB7cf9lBDtLo5xFUuR/Q3dDWsSJOombPcBogZJ+Pf6HQazhfUZ FfaF7tJ2XMitdrNLfGRdk7fRY6pmWshPeygMoBnqFchYSRWsnQ5AmoREzoO12CTjEtzvHXd7m rbdeDanViUIckJc/a8TyftZ8WebcHN4vpVi6Gc5yNQu7m8sZaFZZIrDSymSOENkEwSF7ArtKS kTqF/JBa6lPFyRQZxjcD7hcV4ILwOJZb1vxnJP+T/u0jnK0YYUq7G+jxiHs6iHbK+8xNbUlgs iX7Dk1/59gJRRg/tyGf1hpJvyl6tBW9bkP1XeT/tInz0YoGYgSINkGAA8JfekSFuvfqQcC9dk K32ah5aCPg0GLC7k8iJWJ9i40UaNszp93vTSYpsapyYpAhM3sR6DE6/8+8C68lJZyEO2yojpM ganYGtJoAU988QAnynDpO7MshUyrMzcRhT5Qd6PSezqpfmnxgxRdcYw/Yy9CUzfBcwyHHCJXn rndqJBuWOjVjvJAEBwo/qTvD1xNPKTDz7Js9jlkPqnQzgNBEYCK5h/2YejGibgTuAvM1c5Hke ey3YSSTSTuCdCyoKVAHcD1XL+B/PzmJKXZyAzEF5yo8Ik9TFiFX/y10ioQocYQy7QGCGjDZgS r8QR+uaMhtran7jDErKSXuCUAPsZYhGyUOQGJO8tkc621EaNkr0V65dBRiCQ8jhbYEK/RBdkZ QyEde6qQ0Bzg7ddnhnlBl396cCrH75oPDsfgbJdNEWIH0JzkCZSOp9J5uTXqOQ1ehvr0XvK65 94XvGWfeXf3tZ+g5Jnz/ZYBg11ii8BMTSfjIMOYqRgi7NxaquV3L5zaFypvZ5iS8p8g2EGy1f kXyX4LY0Ogvn8jX3F6GJxROaZ9ToyBRHnk0rmgBE7dB3LeNCTX57X65qX3Gf/qYEsjkQRA6oq Cc/YQchJa2EOnEJIe26a+VopW7/UgCspG25/nzxTzO4ILJfqWZP8gdkRkoiqA5Rf2a40EK4NM 9LkFWh3o38C1THeylMANqX7cUd7vPduqzkcdmG2lj+jpKMaTQ0pGTfjExZDYUZfUlTjIaLQI0 tzLReYSG7ihKmOUyvLNU3KxRXvkotZ2Ge24bseBEYKVkXM+9fT4hHa/Q7l/DQM8Zyb8BN3vqc a+NhbTHEKW/nhPUrltylXVVZnCZVLu2+JCfadKY/hP06bPd73i6c5vIjCjlTz58ej5ncGRil8 ye8Jx96HsDlMyyIlOXH0wzKeDURndrQ0mWLtZZ7h6KSijoHiL6j1f823P/60FdSXvsIyaxtTK fXctYdX53MPKGRwipeicGZh89N0NvPSLABOiME8CEQ6yejkKE0NzYa2mYWe/LoWqgfTjp0c/4 eX+B9LpuMeKLI593hYuYEiVCW09B+aS50EVW643GipYErHoLzPLju1hW4fw/IXU1HRgOf/3hv qUBAM4yA3dSUSaHjhiqUJZyZ5vAjt6RZg3hPMUMucPem/S4RnoxtFrwP5YvSX5jHGVwVkYWcG WnrEFLlVvgPcYQaY+OxKhSUupiW+NeHCpH/Bm7RWnN4bcrlH4CAuO0w26cpYzBdYbx3K8TWia ZeQHyiyT+JiyxXgaCOHbcQ3ZUBxB6iMJl2RIKwL5+CIDW3XCl0Wz8l8OgPQIap6RU4lkPMxB3 aF4EJ4+i0aNX8SzjpwvWpnMr9U0XDDr/gvQi/Df+jtmJkzusgF10fiAoxV0kk1QkN0AWnOdzl V4co//r5ybFiw1Lr87E7MlqJDfGMb4cAs4xG5tofGK9khyNtnDfo/9JDGUU5k1FEEZn+IyyEu VE0TWrZLfTbv/25uFWMZa1KAN3Wbe2zMldn3rAWoOFydcEVpKiFYv7X7Y9x+gS3lZElZTwm08 Wxhavpl8QukcNZadO4DcENFjgV+v0jLgDdmbwAvcPy7Bi5fQ2y6vYuL7xfV3sYNpkAtF8iJpE A8hcCi5c7GeydWcMI7RXUQh696cLultXR9YW5kF4Fm4qQ9awpjJJagQRsos05OaQO7LtCKDeu NO/Ewz7SlBKtYVcnlHexJa2ir8Db41fowVBP2NTaBaM4ZYkl8qE28bgiC8fKHP+pQj/MSdscy JBdmWrnZDhWwuXeMZ63+G3nTBWUILEGPWTs5AAoT/GPNTKErAlN/6IpKOWD4zbmBjQ0oSb24h WP+3qZpEx+6HOPayOq75FsVlfCWFWb2XsnQpBtooStRmlpH3KFQ/5iQGK0V467D4ZzhcsdTy/ A4432PhleLlHD5X0wYlUuuYHu+hYS6/2JT1CRqoCH/jkF5fH/GW5ZLV33TzlJe/uEigRUere/ k1NU4hoM6x2CgHszCoZDErLRam3wzSERVhgB8SYX2WhMUkrHFn3JGnebYhSWMjg8TCGAn9cSd 8EZiBUBqt4xHO1CoJbFJH8p+/hwMN0Z0OW6N6FhqrmD+ZsggJRegfHfEB3EHmxM7RhvvcEDHi Iy6gx6EMBFO6jJrPxXe4AerV3frBpBKZihWhkkBYHQ20s6ULPEmPn7e3GxeVk3Dlb+fAQGGt7 IK0LtIMd7lG9pxa1Jf5qU+7g7djCIDOM19/JAN/qiyTFCZOHRXTEDczsph4TePsH6fPybk73x 8A2U5LcCUAcTZslkU= =E5=9C=A8 2025/12/9 05:49, David Sterba =E5=86=99=E9=81=93: > On Fri, Dec 05, 2025 at 06:34:30PM +1030, Qu Wenruo wrote: >> This is done by: >> >> - Shrink the size of btrfs_bio::mirror_num >> From 32 bits unsigned int to 8 bits u8. >=20 > What is the explanation for this? IIRC the mirror num on raid56 refers > to the device index, You're right, u8 can not cut the max number of devices for RAID6. (RAID5 only has two mirrors, mirror 0 meaning reading from data stripes,= =20 mirror 1 means rebuild using other data and P stripe) BTRFS_MAX_DEVICES() is around 500 for the default 16K node size, which=20 is already beyond 255. Although in the real world it can hardly go that extreme, but without a=20 proper rejection/sanity checks, we can not do the shrink now. I'd like to limit the device number to something more realistic. Would the device limit of 32 cut for both RAID5 and RAID6? (And maybe apply this limit to RAID10/RAID0 too?) Or someone would prefer more devices? Thanks, Qu > the type width should not be too narrow. But if > the semantics are different we can reduce the mirror num in other > structures as well. >=20