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[46.135.14.82]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4792afd3b31sm110871215e9.0.2025.12.06.05.20.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 06 Dec 2025 05:20:06 -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 v3 1/2] ns: pad refcount Date: Sat, 6 Dec 2025 14:19:54 +0100 Message-ID: <20251206131955.780557-2-mjguzik@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20251206131955.780557-1-mjguzik@gmail.com> References: <20251206131955.780557-1-mjguzik@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 0535840003 X-Stat-Signature: nj3f7pmgzyekpot6bug5twy8wg3bfxwx X-Rspam-User: X-HE-Tag: 1765027208-826270 X-HE-Meta: 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 c/P0Du42 yY4znAg/rXSObHp5fK7fV+qGJz7rszhAqsrr7aNGLCWnp7zkMEVOqet0Z4FZknJ3BV+Bokb102cFQoHBd4JTAmFrAuyZXOSfYwBXtCw/+zsdxtvS3y+aMBwNY/Aa2SOXiYn0tOvwFW8uJc0ra/O48Zx5CVzn2ORPGy1c6PGkQUIoqPbSbNItD9kFg++9rrbHYfhYf4BU6kV8I1zeiGqu3GtjqBFKB6pLiwDPiT+7wsjQg3K596vkMvMFbFL6t9fWvXu1ssM8StOeOA3ScSOLJxmin11wOLL+tX8s1lcycW9OEjjGBFxxogFg63wrz8VrA5AKt4+t2NnRT6AS1AASFtkp0++3+cthlusocPG9wjiVm4j1d+M0mWcNLZr+s510mjc1Ibi+yzYpwl39vYnjMAPsb0Bp892FeKjwY 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