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[46.135.14.82]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b7654cf0435sm929432866b.4.2025.11.22.22.31.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 22 Nov 2025 22:31:09 -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, Mateusz Guzik Subject: [PATCH 2/3] ns: pad refcount Date: Sun, 23 Nov 2025 07:30:53 +0100 Message-ID: <20251123063054.3502938-3-mjguzik@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20251123063054.3502938-1-mjguzik@gmail.com> References: <20251123063054.3502938-1-mjguzik@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: E2C1A140008 X-Stat-Signature: ztgywso7u9gfewuaefk99ss19heufaew X-Rspam-User: X-HE-Tag: 1763879471-499040 X-HE-Meta: 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 bYIqPWqp qrXU3Ryv5BLXfI8MwaAwMEctewhJW/cc5KRQ2M+ajv7B+ytiSDl19OpMRqfwDM8qzJ5oSkkf2CZVyKkyHv2sHr/BHUoRFBo9PIyee2tC0mLw/RkqKf0NKASVr/FzOMusVeN9Lwp7rFzT70ylf2Yhpn+s6CcLYRYZr6goEf2kQ20VXWTp036c7bsSZ5mlj15jRAG0iZ0ROLBjB2XlrsBTwURQFsiq+WC9pXW40kTAm2RiCfIgCkuRpdVlWfGRMV5xntbGny5pcp+ExxagDyzxTk7zcQNKQaZb5Rn4k0ADGXz72iRkvO7n3njRTO1OdWDhY0HzEpt3U53kVUzNcV/5LjZ3ifKqEmBpSTdkWuIPhKAjM+Fqq+BMKCSkN8qthr2ki5bkJyrnbL7amL7nKILvkpNDLTA== 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