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 A4CFE389459 for ; Mon, 2 Feb 2026 17:53:56 +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=1770054836; cv=none; b=ZC8bQQYnOiE/CcdGJ4CeZ3APjRXegSWAqJBainMe9E8lJ9Kg+8c4DjtlPlqCRk6DN1sSFTir6dqTAs6/CJxwbrIw0IwyUpMKv1YPs+KIkgVkaTFSOa5BFCzv/wHgjpvbo7q+xfWbblkaYv1xjgGkWADzk84SeACD12cy4XPYtEM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770054836; c=relaxed/simple; bh=v/GL8h8V+LemGAfnudlVdJMDIRWPzEd1NejtNk51f1k=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Pw/tI9cgq3FiOXXjOe3IeUzgcSHWFnF+DgzboD0cLM4p16vjlXgpvFihs22e5msL19Bf8sTXJb2rk42ygE8M2gp4XZbaje27btR63aPVGnZNVMwBsE0vMdrf8WTh7VObaq0sxzOOlWRhhhzAwSh0v4DS0Bc7NZpvHvGG/Igi5fo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=oX5Irr2O; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="oX5Irr2O" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 005E0C116C6; Mon, 2 Feb 2026 17:53:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1770054836; bh=v/GL8h8V+LemGAfnudlVdJMDIRWPzEd1NejtNk51f1k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=oX5Irr2ODZuZgLimb7Nnl2qf50tvPBpHr8Uv1TPjD6ggroqtqJkLfHkMewBhYFgzf B5QKYrd45KdetuqdPFuvBQhSRlBGEhxUVLE1hSAuk90VFGGZ7T2GSnJipkEBGTOncs DUSG4PqzRj7qzWA9Ivw61DT7wQSXYM1Dvw4j9+f/fLH6/7PAeHU2c/g3GtPG0uib3R GrXf5/Jpr20tFW6hjpttuHI8KeitmaPSktuAflNEQjcyvmDgLsE0HoU03vrQcqWz6c OC9Sg7NmpmSoVoZzZtv2rXhyw9pp4xSEdh2sREfKcDku5Obe+rWcS04VaQNw6MjQBB elefOkOOOC5Rw== From: SeongJae Park To: "Liam R. Howlett" Cc: SeongJae Park , Andrew Morton , maple-tree@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Suren Baghdasaryan , Matthew Wilcox , Sidhartha Kumar , Vlastimil Babka , Alice Ryhl , Kuninori Morimoto , Geert Uytterhoeven , Arnd Bergmann , Christian Kujau Subject: Re: [PATCH v3 21/30] maple_tree: Add cp_is_new_root() helper Date: Mon, 2 Feb 2026 09:53:53 -0800 Message-ID: <20260202175354.39717-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Mon, 2 Feb 2026 12:01:53 -0500 "Liam R. Howlett" wrote: > * SeongJae Park [260202 10:56]: > > On Mon, 2 Feb 2026 09:58:31 -0500 "Liam R. Howlett" wrote: > > > > > * SeongJae Park [260131 19:10]: > > > > Hello, > > > > > > > > On Fri, 30 Jan 2026 15:59:26 -0500 "Liam R. Howlett" wrote: > > > > > > > > > Add a helper to do what is needed when the maple copy node contains a > > > > > new root node. This is useful for future commits and is > > > > > self-documenting code. > > > > > > > > > > Signed-off-by: Liam R. Howlett > > > > > --- > > > > > lib/maple_tree.c | 70 ++++++++++++++++++++++++++---------------------- > > > > > 1 file changed, 38 insertions(+), 32 deletions(-) > > > > > > > > > > diff --git a/lib/maple_tree.c b/lib/maple_tree.c > > > > > index 5280fa6d2d6ec..42038e42a4c7e 100644 > > > > > --- a/lib/maple_tree.c > > > > > +++ b/lib/maple_tree.c > > > > > @@ -3337,6 +3337,43 @@ static void mas_spanning_rebalance(struct ma_state *mas, > > > > > mas_spanning_rebalance_loop(mas, mast, count); > > > > > } > > > > > > > > > > +static inline bool cp_is_new_root(struct maple_copy *cp, struct ma_state *mas) > > > > > +{ > > > > > + if (cp->min || cp->max != ULONG_MAX) > > > > > + return false; > > > > > + > > > > > + if (cp->d_count != 1) { > > > > > + enum maple_type mt = maple_arange_64; > > > > > + > > > > > + if (!mt_is_alloc(mas->tree)) > > > > > + mt = maple_range_64; > > > > > + > > > > > + cp->data = cp->d_count; > > > > > + cp->s_count = 0; > > > > > + dst_setup(cp, mas, mt); > > > > > + init_cp_src(cp); > > > > > + node_copy(mas, cp->src[0].node, 0, cp->data, cp->max, maple_copy, > > > > > + cp->dst[0].node, 0, mt); > > > > > + node_finalise(cp->dst[0].node, mt, cp->end + 1); > > > > > + /* > > > > > + * Warning, see cp_leaf_init() comment and rcu_assign_pointer() > > > > > + * documentation. Since this is a new root, there are no > > > > > + * read-side operations that can view it until it is insert into > > > > > + * the tree after an rcu_assign_pointer() call. > > > > > + */ > > > > > + RCU_INIT_POINTER(cp->slot[0], mt_mk_node(cp->dst[0].node, mt)); > > > > > > > > I just found the above makes my build test using an old version compiler fails. > > > > Fortunately, seems it is same to the one we discussed before [1], and same > > > > mitigation like below attached patch works, at least for my test setup. > > > > > > Thanks SJ. > > > > My pleasure :) > > > > > > > > This is still with gcc 8.1.0? > > > > Yes. The test code is available at GitHub [1]. > > > > Nonetheless, another test [2] that is using 9.3.0 was also failing. > > You have two failures: one in 8.1 and one in 9.3? Yes. FYI, I picked the compiler versions for no good reason but just because there were reports of DAMON build failures on the compilers in the past. > > I was planning to test 7.5.0 and ensure everything works, but this > implies my plan will not catch everything? >From Documentation/process/changes.rst, I find minimal version of GCC for building kernel is 8.1. So gcc 7.5.0 might not need to be ensured for? I have no good expertise on planning tests, though. Thanks, SJ [...]