From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 5FA6615A856; Thu, 13 Feb 2025 15:36:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739461019; cv=none; b=qEbsIdlQLt/jsbSPOMSPUom532r5/RkF0OvNwULnpQx9KE8NDxrJHLjGYUVCFro94/+mzudICMD1H4kXTxgqzhJoX3ash6RTm3yAI3kc37n/XeQDBHd+MMxeAGVl1qyHiPQ9iZIuKdP3LBXV5vjcn6Q4ur84+mROoyiLPuujydo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739461019; c=relaxed/simple; bh=YjmRhpOpN1Th8fe/4DXRLkjvN0+ozNUvEbfLRbpBe+E=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=WoYT5xiELKiaNhuJpS+LuSk/rqIHG7aOc8DX3wOUI1PNQiMDLhiRKHcr86kCoXOjeQVtoBH00T9+P5f3ykfgBHOw1xvOs2v5KmToKZ4bzVp0ppfa0EgW35IskGzc4BkljJwnt/gUFphW87fthOnnXf0Z2M24X2t+gUG9NOpXK4M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=LbQe45tf; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="LbQe45tf" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D6799C4CED1; Thu, 13 Feb 2025 15:36:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1739461019; bh=YjmRhpOpN1Th8fe/4DXRLkjvN0+ozNUvEbfLRbpBe+E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=LbQe45tfhEXMO4Ksvy8bJ8BMluDzpkbJfkL0v3MHadee2ug8GR0os9ljrEXXiJofF NZv2asQzsyM3H8Bg0lbIBYlCp4YDHke8MTN+JIQqb3uwiWb5zGqE7noqAzRjDB84oT WC3/8u4eLWsFv9mA3XejhPtx35K5/HDHE+qh1/N4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Wei Yang , "Liam R. Howlett" , Sidhartha Kumar , Lorenzo Stoakes , Andrew Morton Subject: [PATCH 6.6 247/273] maple_tree: simplify split calculation Date: Thu, 13 Feb 2025 15:30:19 +0100 Message-ID: <20250213142417.194040594@linuxfoundation.org> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250213142407.354217048@linuxfoundation.org> References: <20250213142407.354217048@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Wei Yang commit 4f6a6bed0bfef4b966f076f33eb4f5547226056a upstream. Patch series "simplify split calculation", v3. This patch (of 3): The current calculation for splitting nodes tries to enforce a minimum span on the leaf nodes. This code is complex and never worked correctly to begin with, due to the min value being passed as 0 for all leaves. The calculation should just split the data as equally as possible between the new nodes. Note that b_end will be one more than the data, so the left side is still favoured in the calculation. The current code may also lead to a deficient node by not leaving enough data for the right side of the split. This issue is also addressed with the split calculation change. [Liam.Howlett@Oracle.com: rephrase the change log] Link: https://lkml.kernel.org/r/20241113031616.10530-1-richard.weiyang@gmail.com Link: https://lkml.kernel.org/r/20241113031616.10530-2-richard.weiyang@gmail.com Fixes: 54a611b60590 ("Maple Tree: add new data structure") Signed-off-by: Wei Yang Reviewed-by: Liam R. Howlett Cc: Sidhartha Kumar Cc: Lorenzo Stoakes Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- lib/maple_tree.c | 23 ++++++----------------- 1 file changed, 6 insertions(+), 17 deletions(-) --- a/lib/maple_tree.c +++ b/lib/maple_tree.c @@ -1870,11 +1870,11 @@ static inline int mab_no_null_split(stru * Return: The first split location. The middle split is set in @mid_split. */ static inline int mab_calc_split(struct ma_state *mas, - struct maple_big_node *bn, unsigned char *mid_split, unsigned long min) + struct maple_big_node *bn, unsigned char *mid_split) { unsigned char b_end = bn->b_end; int split = b_end / 2; /* Assume equal split. */ - unsigned char slot_min, slot_count = mt_slots[bn->type]; + unsigned char slot_count = mt_slots[bn->type]; /* * To support gap tracking, all NULL entries are kept together and a node cannot @@ -1907,18 +1907,7 @@ static inline int mab_calc_split(struct split = b_end / 3; *mid_split = split * 2; } else { - slot_min = mt_min_slots[bn->type]; - *mid_split = 0; - /* - * Avoid having a range less than the slot count unless it - * causes one node to be deficient. - * NOTE: mt_min_slots is 1 based, b_end and split are zero. - */ - while ((split < slot_count - 1) && - ((bn->pivot[split] - min) < slot_count - 1) && - (b_end - split > slot_min)) - split++; } /* Avoid ending a node on a NULL entry */ @@ -2402,7 +2391,7 @@ static inline struct maple_enode static inline unsigned char mas_mab_to_node(struct ma_state *mas, struct maple_big_node *b_node, struct maple_enode **left, struct maple_enode **right, struct maple_enode **middle, - unsigned char *mid_split, unsigned long min) + unsigned char *mid_split) { unsigned char split = 0; unsigned char slot_count = mt_slots[b_node->type]; @@ -2415,7 +2404,7 @@ static inline unsigned char mas_mab_to_n if (b_node->b_end < slot_count) { split = b_node->b_end; } else { - split = mab_calc_split(mas, b_node, mid_split, min); + split = mab_calc_split(mas, b_node, mid_split); *right = mas_new_ma_node(mas, b_node); } @@ -2905,7 +2894,7 @@ static int mas_spanning_rebalance(struct mast->bn->b_end--; mast->bn->type = mte_node_type(mast->orig_l->node); split = mas_mab_to_node(mas, mast->bn, &left, &right, &middle, - &mid_split, mast->orig_l->min); + &mid_split); mast_set_split_parents(mast, left, middle, right, split, mid_split); mast_cp_to_nodes(mast, left, middle, right, split, mid_split); @@ -3413,7 +3402,7 @@ static int mas_split(struct ma_state *ma if (mas_push_data(mas, height, &mast, false)) break; - split = mab_calc_split(mas, b_node, &mid_split, prev_l_mas.min); + split = mab_calc_split(mas, b_node, &mid_split); mast_split_data(&mast, mas, split); /* * Usually correct, mab_mas_cp in the above call overwrites