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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B3379CDB483 for ; Mon, 16 Oct 2023 09:02:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232649AbjJPJC2 (ORCPT ); Mon, 16 Oct 2023 05:02:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41420 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233223AbjJPJCR (ORCPT ); Mon, 16 Oct 2023 05:02:17 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0046BF2 for ; Mon, 16 Oct 2023 02:02:15 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 19B09C433C7; Mon, 16 Oct 2023 09:02:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1697446935; bh=kUZceZ+21J2njF36RXROmt73kTmzX/fyq43l4mSxlyc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=eT6WxS3ymO+WoPMwhnuz0/J0EJEoPIbiOmqYvnU01fGDC6lckarVyRE7mcH2mCMsp /N4vspawurx/kbFXdG/HlkSMBly8cg5qTlI1n8U/He8DLcCApQT0nwc23RtR7mHsn1 ZYH10BVCp4f2vfDEkZd59TiEgaY0eq/AopJjPxgM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Halil Pasic , Nils Hoppmann , Wenjia Zhang , Dust Li , "David S. Miller" , Sasha Levin Subject: [PATCH 6.1 063/131] net/smc: Fix pos miscalculation in statistics Date: Mon, 16 Oct 2023 10:40:46 +0200 Message-ID: <20231016084001.632609399@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231016084000.050926073@linuxfoundation.org> References: <20231016084000.050926073@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Nils Hoppmann [ Upstream commit a950a5921db450c74212327f69950ff03419483a ] SMC_STAT_PAYLOAD_SUB(_smc_stats, _tech, key, _len, _rc) will calculate wrong bucket positions for payloads of exactly 4096 bytes and (1 << (m + 12)) bytes, with m == SMC_BUF_MAX - 1. Intended bucket distribution: Assume l == size of payload, m == SMC_BUF_MAX - 1. Bucket 0 : 0 < l <= 2^13 Bucket n, 1 <= n <= m-1 : 2^(n+12) < l <= 2^(n+13) Bucket m : l > 2^(m+12) Current solution: _pos = fls64((l) >> 13) [...] _pos = (_pos < m) ? ((l == 1 << (_pos + 12)) ? _pos - 1 : _pos) : m For l == 4096, _pos == -1, but should be _pos == 0. For l == (1 << (m + 12)), _pos == m, but should be _pos == m - 1. In order to avoid special treatment of these corner cases, the calculation is adjusted. The new solution first subtracts the length by one, and then calculates the correct bucket by shifting accordingly, i.e. _pos = fls64((l - 1) >> 13), l > 0. This not only fixes the issues named above, but also makes the whole bucket assignment easier to follow. Same is done for SMC_STAT_RMB_SIZE_SUB(_smc_stats, _tech, k, _len), where the calculation of the bucket position is similar to the one named above. Fixes: e0e4b8fa5338 ("net/smc: Add SMC statistics support") Suggested-by: Halil Pasic Signed-off-by: Nils Hoppmann Reviewed-by: Halil Pasic Reviewed-by: Wenjia Zhang Reviewed-by: Dust Li Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- net/smc/smc_stats.h | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/net/smc/smc_stats.h b/net/smc/smc_stats.h index 4dbc237b7c19e..ee22d6f9a86aa 100644 --- a/net/smc/smc_stats.h +++ b/net/smc/smc_stats.h @@ -93,13 +93,14 @@ do { \ typeof(_smc_stats) stats = (_smc_stats); \ typeof(_tech) t = (_tech); \ typeof(_len) l = (_len); \ - int _pos = fls64((l) >> 13); \ + int _pos; \ typeof(_rc) r = (_rc); \ int m = SMC_BUF_MAX - 1; \ this_cpu_inc((*stats).smc[t].key ## _cnt); \ - if (r <= 0) \ + if (r <= 0 || l <= 0) \ break; \ - _pos = (_pos < m) ? ((l == 1 << (_pos + 12)) ? _pos - 1 : _pos) : m; \ + _pos = fls64((l - 1) >> 13); \ + _pos = (_pos <= m) ? _pos : m; \ this_cpu_inc((*stats).smc[t].key ## _pd.buf[_pos]); \ this_cpu_add((*stats).smc[t].key ## _bytes, r); \ } \ @@ -139,9 +140,12 @@ while (0) do { \ typeof(_len) _l = (_len); \ typeof(_tech) t = (_tech); \ - int _pos = fls((_l) >> 13); \ + int _pos; \ int m = SMC_BUF_MAX - 1; \ - _pos = (_pos < m) ? ((_l == 1 << (_pos + 12)) ? _pos - 1 : _pos) : m; \ + if (_l <= 0) \ + break; \ + _pos = fls((_l - 1) >> 13); \ + _pos = (_pos <= m) ? _pos : m; \ this_cpu_inc((*(_smc_stats)).smc[t].k ## _rmbsize.buf[_pos]); \ } \ while (0) -- 2.40.1