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[46.135.14.82]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-64750a90d14sm17859981a12.10.2025.12.03.01.29.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Dec 2025 01:29:02 -0800 (PST) From: Mateusz Guzik To: oleg@redhat.com Cc: brauner@kernel.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, linux-mm@kvack.org, willy@infradead.org, Mateusz Guzik Subject: [PATCH v2 1/2] ns: pad refcount Date: Wed, 3 Dec 2025 10:28:50 +0100 Message-ID: <20251203092851.287617-2-mjguzik@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20251203092851.287617-1-mjguzik@gmail.com> References: <20251203092851.287617-1-mjguzik@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: C7CBF1C0013 X-Stat-Signature: wbyw65x8rj1eeabtepcumybm6xj9iwux X-HE-Tag: 1764754144-785067 X-HE-Meta: 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 Mzxm7myt 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 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: Note no effort is made to make sure structs embedding the namespace are themselves aligned, so this is not guaranteed to eliminate cacheline bouncing due to refcount management. Signed-off-by: Mateusz Guzik --- include/linux/ns/ns_common_types.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/include/linux/ns/ns_common_types.h b/include/linux/ns/ns_common_types.h index b332b019b29c..0014fbc1c626 100644 --- a/include/linux/ns/ns_common_types.h +++ b/include/linux/ns/ns_common_types.h @@ -108,11 +108,13 @@ extern const struct proc_ns_operations utsns_operations; * @ns_tree: namespace tree nodes and active reference count */ struct ns_common { + struct { + refcount_t __ns_ref; /* do not use directly */ + } ____cacheline_aligned_in_smp; u32 ns_type; struct dentry *stashed; const struct proc_ns_operations *ops; unsigned int inum; - refcount_t __ns_ref; /* do not use directly */ union { struct ns_tree; struct rcu_head ns_rcu; -- 2.48.1