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 AA5141EB36 for ; Wed, 25 Sep 2024 10:02:43 +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=1727258563; cv=none; b=gTocZdHEo9t9jNAtOP0Mysj+p1px6p9+DviwaAgh9BJH72TbmnXjzKGZuEXEzEYo0hmpNi1q40b5UyBGmBcqwoglQ/CHTb+hHJjXJ+4m0pnFw4+P2Hq3TvAnsf4AQlwBWcdDMfK/xO98sxJQKa5hCQoln3EAYlCw2jRZdlUr75g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727258563; c=relaxed/simple; bh=m41ClxIqRYjsfKg0RcVL6Lh14U3/GraobjIECFfk4E8=; h=Date:To:From:Subject:Message-Id; b=DrEl6cA4iLQh0DqFDE+G4wFFIXL9wGuE/CptNQsKSM0c+olegKxCRwzTJ/Og0xNnY58dLjdTB/91flosd0fA2cGxhgRvkxR0gMKHZMPfO0oltsiTvDRnP6WL8CLeIXrxFuFFyU5NOC73/YZCDddOX9MeyTaZZFZdap8FOksU4mc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=WE953Fva; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="WE953Fva" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 25C5CC4CEC3; Wed, 25 Sep 2024 10:02:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1727258563; bh=m41ClxIqRYjsfKg0RcVL6Lh14U3/GraobjIECFfk4E8=; h=Date:To:From:Subject:From; b=WE953FvaYKIFiwc6rOMI62z8cz2mq3mRz5wDioIsIk+lRm/NYcKdu0Rr6NY08P0Nz XFVDqKnszpzk54LwI4qnIw4WxnnNfOvO2FiW3KPjltWeIydSmQoxEeJ6CTqFnNJER/ m4q4sZVItLXf2n6hqe9E20IJtko2oOA407+6Acys= Date: Wed, 25 Sep 2024 03:02:42 -0700 To: mm-commits@vger.kernel.org,Liam.Howlett@Oracle.com,richard.weiyang@gmail.com,akpm@linux-foundation.org From: Andrew Morton Subject: + maple_tree-i-is-always-less-than-or-equal-to-mas_end.patch added to mm-unstable branch Message-Id: <20240925100243.25C5CC4CEC3@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: maple_tree: i is always less than or equal to mas_end has been added to the -mm mm-unstable branch. Its filename is maple_tree-i-is-always-less-than-or-equal-to-mas_end.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/maple_tree-i-is-always-less-than-or-equal-to-mas_end.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Wei Yang Subject: maple_tree: i is always less than or equal to mas_end Date: Wed, 11 Sep 2024 14:27:58 +0000 Patch series "refine mas_mab_cp()". By analysis of the code, one condition check can be removed and one case would hit a redundant assignment. This patch (of 2): mas_mab_cp() copy range [mas_start, mas_end] inclusively from a maple_node to maple_big_node. This implies mas_start <= mas_end. Based on the relationship of mas_start and mas_end, we can have the following four cases: | mas_start == mas_end | mas_start < mas_end ---------------+----------------------+---------------------- mas_start == 0 | 1 | 2 ---------------+----------------------+---------------------- mas_start != 0 | 3 | 4 We can see in all these four cases, i is always less than or equal to mas_end after finish the loop: Case 1: After assign pivot 0, i is set to 1, which is bigger than mas_end 0. So it jumps to complete and skip the check. Case 2: After assign pivot 0, i is set to 1. ∵ (mas_start < mas_end) && (mas_start == 0) ==> (1 <= mas_end) ∵ (i == 1) && (1 <= mas_end) ==> (i <= mas_end) ∴ Before loop, we have (i <= mas_end). And we still hold this if it skips the loop. For example, (i == mas_end). Now let's see what happens in the loop: ∵ piv_end = min(mas_end, mt_pivots[mt]) ==> (piv_end <= mas_end) ∵ loop condition is (i < piv_end) ==> (i <= piv_end) on finish the loop both normally or break ∵ (i <= piv_end) && (piv_end <= mas_end) ==> (i <= mas_end) ∴ After loop, we still get (i <= mas_end) in this case Case 3: This case would skip both if clause and loop. So when it comes to the check, i is still mas_start which equals to mas_end. Case 4: This case would skip the if clause. ∵ (mas_start < mas_end) && (i == mas_start) ==> (i < mas_end) ∴ Before loop, we have (i < mas_end). The loop process is similar with Case 2, so we get the same result. Now we can conclude in all cases, we get (i <= mas_end) when doing check. Then it is not necessary to do the check. Link: https://lkml.kernel.org/r/20240911142759.20989-1-richard.weiyang@gmail.com Link: https://lkml.kernel.org/r/20240911142759.20989-2-richard.weiyang@gmail.com Signed-off-by: Wei Yang Reviewed-by: Liam R. Howlett Signed-off-by: Andrew Morton --- lib/maple_tree.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) --- a/lib/maple_tree.c~maple_tree-i-is-always-less-than-or-equal-to-mas_end +++ a/lib/maple_tree.c @@ -1949,8 +1949,7 @@ static inline void mas_mab_cp(struct ma_ goto complete; } - if (likely(i <= mas_end)) - b_node->pivot[j] = mas_safe_pivot(mas, pivots, i, mt); + b_node->pivot[j] = mas_safe_pivot(mas, pivots, i, mt); complete: b_node->b_end = ++j; _ Patches currently in -mm which might be from richard.weiyang@gmail.com are maple_tree-i-is-always-less-than-or-equal-to-mas_end.patch maple_tree-goto-complete-directly-on-a-pivot-of-0.patch