From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f46.google.com (mail-wm1-f46.google.com [209.85.128.46]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BD621395240 for ; Mon, 13 Apr 2026 21:06:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.46 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776114393; cv=none; b=ia0id1Mu1VtQ/d00V0zPZE+hr6Qi912reyV2dfMqZ05kO6pqn7HTSPK2DvPxRa08Zn7XVy+8ienKFVXkjCD1RHFLWX0YBA2RX7BBK5reafzgvqloEj5tXwyr+PuRtfWK6m5XfQCzLcSIzr27YKKUEXYRb2UrhixuhfBwZb2to90= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776114393; c=relaxed/simple; bh=y3X4Q1wuaiYro/3UQY7swAXd4RhfbzRFT9BkiQ88xho=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=FK8iuBK+knA5fx3PvYZHF6WtO2M31t36o5b3welPhNRhYi31pMs5WP4Sm3ZMcLFLiF3QNmyI4ojE6cAM3fRF9JBaLX7UES3xgQlmHPxKWJ4Ul9EYrIEPasTR9TD+LEq+eT9IgPITlBT7W7zqb2npWeuOW2qsz+9RjfEDFcCWEXI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=hackers.camp; spf=pass smtp.mailfrom=gmail.com; arc=none smtp.client-ip=209.85.128.46 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=hackers.camp Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Received: by mail-wm1-f46.google.com with SMTP id 5b1f17b1804b1-4889d0a9df0so5844115e9.3 for ; Mon, 13 Apr 2026 14:06:29 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1776114388; x=1776719188; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=tDFE/x9etytc+EWBgqwOsTxdVZ9Oqe0zFdU+mEte1zQ=; b=fJTBWdHcItW2FBfpi0FbJMF6CX30YS8i7NuSi7wxJXY4hvuFPxtzVEKq3EbSLOghWm jqcq6ISto4tcQ72W0CyYNP+mqQ4W1WulHBSBYOHuNdKkLh+wOXnsKa68YdW/XAgx9GGB DUr2t44XL9Jc7yhe1W8QtyWn/EUOP5RnTUD/dSNY7UdhzkBBEaA1GoO7HsEsk0n6JdBO 7I/SzThdm6kwh6zE8w0oj05YfDC8fwDbIF0WnybHs7nh1mpW7k1qcCaoTGNeHEUZDD1F 5zezp+hTWDNDcoj4lLyopLdqGRZgE3/dgrQ4GA3MEyje+TOodWUz0hwnqOoelG2wuM1t oE5w== X-Forwarded-Encrypted: i=1; AFNElJ+eW4vAySqWGV4KkpZqH/+1hod3NQdG6A7xL8DQW+ydZwQ2j0oft3AHegeDJLUfvfff9psUIKuNhYmH5vQ=@vger.kernel.org X-Gm-Message-State: AOJu0Yyi5U1E4GTaVu2AO/9mxfebmkC+yMNfjDTchqoL24CB9pBPFt9p jRlixET8NfFib4fy4KAYyMLlCpFKRsf7Ckf4GGVORKLKJb5USCmpInuv X-Gm-Gg: AeBDievVmuunCb8xa9mDhwsmOMPXVVpx+ucr6LOXQm1ftvZBwfMckzla17pLha1DutD yb3Vl9+s+pEnMkpE8ZqJN5m5R84AVLidf7w6tn9IUX+hH3Bg6vPnqefEsSbHj6SsTSsOekWz9uP ixID6YIO+HJQ5cdotwlhEC2N7b1dXVfCH9ZYPLow8mcLX5qs7pejwcwNHgOIqrMnOQjRHgdSD0P /1sArOJep2aN5ZnFblb9ySTRJPuATU/yDpxe/eFJ4mHJvz0B6lYC+o9UJpYhWkPh3jRi80KI9Lq 3vIm+9ImGesy9xLCOYILQqHYEbsqo3JH762HZOMxBN5rQXiHqYkmknus+9ePriUaxR+c8jMW9rJ H7O7wM4O2UjCiOyjrOI1oemPN/txa6zpDWnzQmSgF5KtG4PLWsbIp9c7HqaTwZAaYSNwJsLIohU 65Hn75AsPwNQxUTxvSo0kliLkJs5MPY0fr/jD09jTvy78JaOdmHkF/hR0jZwAVeXFxbCeHLyY3d bV0 X-Received: by 2002:a05:6000:161a:b0:43d:55b3:a200 with SMTP id ffacd0b85a97d-43d642c97e0mr6616599f8f.4.1776114387967; Mon, 13 Apr 2026 14:06:27 -0700 (PDT) Received: from spartian-1.home ([2a01:cb1c:784:2f00:708:2805:7128:7a75]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43d63e5c98fsm35130020f8f.35.2026.04.13.14.06.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 13 Apr 2026 14:06:27 -0700 (PDT) From: Aurelien DESBRIERES To: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Aurelien DESBRIERES , viro@zeniv.linux.org.uk, brauner@kernel.org, willy@infradead.org, djwong@kernel.org, adilger@dilger.ca, pfalcato@suse.de Subject: [PATCH v2 08/11] ftrfs: add CRC32 checksumming and Reed-Solomon FEC skeleton Date: Tue, 14 Apr 2026 01:05:49 +0200 Message-ID: <20260413230601.525400-9-aurelien@hackers.camp> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260413230601.525400-1-aurelien@hackers.camp> References: <20260413230601.525400-1-aurelien@hackers.camp> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Implement data integrity layer: - ftrfs_crc32(): CRC32 wrapper via kernel crc32_le(), used for per-inode and per-superblock checksums - init_gf_tables(): initialize GF(2^8) Galois Field lookup tables (primitive polynomial 0x1d) for Reed-Solomon arithmetic - gf_mul(): GF(2^8) multiplication via log/exp tables - ftrfs_rs_encode(): systematic Reed-Solomon encoder over FTRFS_SUBBLOCK_DATA bytes with FTRFS_RS_PARITY check symbols The RS encoder operates on sub-blocks within each 4096-byte data block. Decoding (error correction) is not yet implemented. Signed-off-by: Aurelien DESBRIERES --- fs/ftrfs/edac.c | 84 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 84 insertions(+) create mode 100644 fs/ftrfs/edac.c diff --git a/fs/ftrfs/edac.c b/fs/ftrfs/edac.c new file mode 100644 index 000000000..ebe676c98 --- /dev/null +++ b/fs/ftrfs/edac.c @@ -0,0 +1,84 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * FTRFS — EDAC layer: CRC32 + Reed-Solomon FEC + * Author: roastercode - Aurelien DESBRIERES + */ + +#include +#include +#include +#include "ftrfs.h" + +/* Reed-Solomon FEC context */ +static uint8_t gf_exp[256]; +static uint8_t gf_log[256]; +static bool rs_initialized; + +/* Initialize Galois Field tables */ +static void init_gf_tables(void) +{ + uint8_t x = 1; + + for (int i = 0; i < 255; i++) { + gf_exp[i] = x; + gf_log[x] = i; + x = (x << 1) ^ ((x & 0x80) ? 0x1d : 0); + } + gf_exp[255] = gf_exp[0]; + rs_initialized = true; +} + +/* Galois Field multiplication */ +static uint8_t gf_mul(uint8_t a, uint8_t b) +{ + if (a == 0 || b == 0) + return 0; + return gf_exp[(gf_log[a] + gf_log[b]) % 255]; +} + +/* Reed-Solomon encoding */ +int ftrfs_rs_encode(uint8_t *data, uint8_t *parity) +{ + uint8_t msg[FTRFS_SUBBLOCK_DATA + FTRFS_RS_PARITY]; + + if (!rs_initialized) + init_gf_tables(); + + memset(msg, 0, sizeof(msg)); + memcpy(msg, data, FTRFS_SUBBLOCK_DATA); + + for (int i = 0; i < FTRFS_SUBBLOCK_DATA; i++) { + uint8_t feedback = gf_mul(msg[i], gf_exp[FTRFS_RS_PARITY]); + + if (feedback != 0) { + for (int j = 1; j <= FTRFS_RS_PARITY; j++) + msg[FTRFS_SUBBLOCK_DATA + j - 1] ^= gf_mul(msg[i], gf_exp[j]); + } + } + + memcpy(parity, msg + FTRFS_SUBBLOCK_DATA, FTRFS_RS_PARITY); + return 0; +} + +/* Reed-Solomon decoding (simplified for now) */ +int ftrfs_rs_decode(uint8_t *data, uint8_t *parity) +{ + if (!rs_initialized) + init_gf_tables(); + + /* For now, assume no errors (full decoding to be implemented) */ + return 0; +} + +/* + * ftrfs_crc32 - compute CRC32 checksum + * @buf: data buffer + * @len: length in bytes + * + * Returns CRC32 checksum. Uses kernel's hardware-accelerated CRC32 + * (same as ext4/btrfs). + */ +__u32 ftrfs_crc32(const void *buf, size_t len) +{ + return crc32_le(0xFFFFFFFF, buf, len) ^ 0xFFFFFFFF; +} -- 2.52.0