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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (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 65DCDCD4851 for ; Tue, 12 May 2026 05:23:39 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [127.0.0.1]) by lists.ozlabs.org (Postfix) with ESMTP id 4gF4kd2c4vz2yKw; Tue, 12 May 2026 15:23:37 +1000 (AEST) Authentication-Results: lists.ozlabs.org; arc=none smtp.remote-ip="2607:7c80:54:3::133" ARC-Seal: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1778563417; cv=none; b=hnBGbAAAgPD4Lc/Fs8pPiYQg7yvZBmXCmOLbG60aR5r7O/yz6k+TlhipL6Nv2qBhLrHpC6xOQYh3P48+PMzTcz4mTrbV0Qagp0v/sdjk8/7yQiI8KL+iR+4gAmU0z00sFBbxMeJ33V4OJvNU3qd8PPpsH3BP/+7GzEelH5+3aQ+y7sDnu60db4q2+yUqL60kAyrdbPr4zb6wGEVPp9csw+aARbOY4VuVHPVd9gdD+vLDva5pBGwVML4rtxAHYUIriJkpbn5wDGeKFMsRlLoF1Uqfc3nYSKy1/wPsAlMXrqET+h9R2yvvbYESJhzMxsi+Ent9P7LOKuYBtilv9M/eZQ== ARC-Message-Signature: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1778563417; c=relaxed/relaxed; bh=lk9xgGRX6KmTgHi8yeCmJiNwyDWaauERdGqaOWPOxNE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=DH7m+W3mcoa7aBlCq2sNkUgD9jcVkQOEuQ8NBnDqGPT6xFuHAdHoIGs9JuMMvXI2mLU6itp9ELXfVUMXsNGLrvMTaOa3Yh1EoD1kRMAUY3W0lDQfbsa6TFVmeXeRZgnkVNK/MiT77aJ6Y0QAM7Kq5mOLY4kcR93ufSJmWSDlicB7rLnT13tRR33CALeSyZhRUhU9GIkUW6OzQbwxoboJzmj3nnySTb5NnDEClqZJMQZYg5T+D2aLp/qL/qIO3EdoOn+phPJhujKMoPOY/qV83vjPIWlj8ODddGM1/KqIkyMNszptCQCgdgxhV9vDJn113JuDdPfRr3ulC3bFqZjRiA== ARC-Authentication-Results: i=1; lists.ozlabs.org; dmarc=fail (p=none dis=none) header.from=lst.de; dkim=pass (2048-bit key; secure) header.d=infradead.org header.i=@infradead.org header.a=rsa-sha256 header.s=bombadil.20210309 header.b=l9QL8FjZ; dkim-atps=neutral; spf=none (client-ip=2607:7c80:54:3::133; helo=bombadil.infradead.org; envelope-from=batv+9f3c1ea353498f61ccd0+8297+infradead.org+hch@bombadil.srs.infradead.org; receiver=lists.ozlabs.org) smtp.mailfrom=bombadil.srs.infradead.org Authentication-Results: lists.ozlabs.org; dmarc=fail (p=none dis=none) header.from=lst.de Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; secure) header.d=infradead.org header.i=@infradead.org header.a=rsa-sha256 header.s=bombadil.20210309 header.b=l9QL8FjZ; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=none (no SPF record) smtp.mailfrom=bombadil.srs.infradead.org (client-ip=2607:7c80:54:3::133; helo=bombadil.infradead.org; envelope-from=batv+9f3c1ea353498f61ccd0+8297+infradead.org+hch@bombadil.srs.infradead.org; receiver=lists.ozlabs.org) Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:3::133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange x25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4gF4kX73bMz2yGf for ; Tue, 12 May 2026 15:23:30 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From:Sender :Reply-To:Content-Type:Content-ID:Content-Description; bh=lk9xgGRX6KmTgHi8yeCmJiNwyDWaauERdGqaOWPOxNE=; b=l9QL8FjZ7+E5EBMHVT0/gRU+vG eamJddBD4ZK2GrbpvQkqMeld+GJF1U8zc0XZKnsp3cbar4kkaiZ6prkVXfW5QHNmKwOko9E0CAaCG K6nseoa3cjAeTPtKZ1mDOZz3Dzv+qSAlvUcrAyqlkJ2cBKvc5q8k6SA3W89evJiahuLj7tRPCblYk 67mWrhIWdo6GJvmWsCiVx9KGhqz2Lx4zA1NFzvV0+RkG0BQpZnrKCUUHTUgRJldV6EUY+DHzEmOhX kjYI6hqQsKxKtPUx90JTmkimbSZePBIxTp2pD0+LosuqW4BQq12FxpZ35qupJ1ptq5qWURy7fZluC n3JlY+qA==; Received: from 2a02-8389-2341-5b80-decc-1a96-daaa-a2cc.cable.dynamic.v6.surfer.at ([2a02:8389:2341:5b80:decc:1a96:daaa:a2cc] helo=localhost) by bombadil.infradead.org with esmtpsa (Exim 4.99.1 #2 (Red Hat Linux)) id 1wMfZz-0000000FaPv-0bKv; Tue, 12 May 2026 05:22:51 +0000 From: Christoph Hellwig To: Andrew Morton Cc: Catalin Marinas , Will Deacon , Ard Biesheuvel , Huacai Chen , WANG Xuerui , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , "Christophe Leroy (CS GROUP)" , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Herbert Xu , Dan Williams , Chris Mason , David Sterba , Arnd Bergmann , Song Liu , Yu Kuai , Li Nan , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-crypto@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-arch@vger.kernel.org, linux-raid@vger.kernel.org Subject: [PATCH 01/19] btrfs: require at least 4 devices for RAID 6 Date: Tue, 12 May 2026 07:20:41 +0200 Message-ID: <20260512052230.2947683-2-hch@lst.de> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260512052230.2947683-1-hch@lst.de> References: <20260512052230.2947683-1-hch@lst.de> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html While the RAID6 algorithm could in theory support 3 devices by just copying the data disk to the two parity disks, this version is not only useless because it is a suboptimal version of 3-way mirroring, but also broken with various crashes and incorrect parity generation in various architecture-optimized implementations. Disallow it similar to mdraid which requires at least 4 devices for RAID 6. Fixes: 53b381b3abeb ("Btrfs: RAID5 and RAID6") Signed-off-by: Christoph Hellwig --- fs/btrfs/volumes.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index a88e68f90564..0b54b97bdad8 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -159,7 +159,7 @@ const struct btrfs_raid_attr btrfs_raid_array[BTRFS_NR_RAID_TYPES] = { .sub_stripes = 1, .dev_stripes = 1, .devs_max = 0, - .devs_min = 3, + .devs_min = 4, .tolerated_failures = 2, .devs_increment = 1, .ncopies = 1, -- 2.53.0