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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 07:56:26 -0800 Message-ID: <20260202155627.16416-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam12 X-Stat-Signature: jopwobzjr3se4pt7dnzc9ryhhf1ujynb X-Rspamd-Queue-Id: C84A6140007 X-Rspam-User: X-HE-Tag: 1770047796-91829 X-HE-Meta: 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 cTHBtMs2 SCweIr7TpeABqutQ/ryv7VMdJrmmdcHvS9blf9NX4wtatfk78dMMpqpJClhGfPkrMPki1UQpVRWe3BSyITgFMaC7kHkao4YwudMDsTPuiBxhcs3kaBWI3zv8Wia0MF66iSRcNLI80v9DCxOWo/MyAgcTw7gbwOfqepCGBFGWX2AnQNzVB3GU9R/JH8efgM73OFbbs7VCb4WvFQhTZ5O1Iel9KzstmGGT3GBSumbW8wsUBMHiqSM298M67Id7Tw+os+v6uFxkPO/FIsxqihFLpAutwJuWX9QO7xEEAz4dFzxtDnGN04Vx18FDYij5jsWoP46h1G/Pj5QthSpEcwnJH6Wbc/8AP/Kezj3oC7ZReg5FA3jo= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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. [1] https://github.com/damonitor/damon-tests/blob/master/corr/tests/build_m68k.sh [2] https://github.com/damonitor/damon-tests/blob/master/corr/tests/build_arm64.sh Thanks, SJ [...]