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[2001:1c00:3406:8400:8d28:76bd:624c:ed78]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b87f3b05154sm513246666b.44.2026.01.21.05.52.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 21 Jan 2026 05:52:50 -0800 (PST) From: Boudewijn van der Heide To: liam.howlett@oracle.com Cc: akpm@linux-foundation.org, aliceryhl@google.com, andrewjballance@gmail.com, boudewijn@delta-utec.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, maple-tree@lists.infradead.org Subject: Re: [PATCH v2] maple_tree: Add lockdep assertion in mas_dup_alloc() Date: Wed, 21 Jan 2026 14:52:38 +0100 Message-ID: <20260121135238.26578-1-boudewijn@delta-utec.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 1FFFE1C000D X-Rspam-User: X-Stat-Signature: rmrygrs1535ci8cymc34qnggymzwkgsi X-Rspamd-Server: rspam08 X-HE-Tag: 1769003572-353159 X-HE-Meta: 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 l2NGNCBJ 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000024, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Thanks for the review! That makes sense, I overlooked this detail in v2. We should absolutely just check in __mt_dup(), like mtree_dup() does for actual locks. I took a closer look at __mt_dup() and mtree_dup(), and I saw that mtree_dup() locks both the new and old maple_tree. So I think it also makes sense for us to assert both trees in __mt_dup(), like this: @@ -6379,6 +6379,9 @@ int __mt_dup(struct maple_tree *mt, struct maple_tree *new, gfp_t gfp) MA_STATE(mas, mt, 0, 0); MA_STATE(new_mas, new, 0, 0); + lockdep_assert(mt_write_locked(new)); + lockdep_assert(mt_write_locked(mt)); + mas_dup_build(&mas, &new_mas, gfp); if (unlikely(mas_is_err(&mas))) { ret = xa_err(mas.node); Does that look good to you for v3? > > /* Allocate memory for child nodes. */ > > type = mte_node_type(mas->node); > > new_slots = ma_slots(new_node, type); > > -- > > 2.47.3 > > > > > Thanks, Boudewijn