From nobody Fri Dec 19 15:00:25 2025 Received: from mail-wm1-f50.google.com (mail-wm1-f50.google.com [209.85.128.50]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3ED152D592A for ; Sat, 6 Dec 2025 13:20:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.50 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765027210; cv=none; b=D3pxZvN3vyzk7jwzqBShU/ZhTOpiO2MDMACawpHNHdPOr+anfQFmVA0ISQMfA2vvlFqbV+cSHvk47X1NqQN6nXfXMrHipc3cl2Ctm7qY4kAYhkYtZwzo/RdOzAK6TQfSB5DsQSfQmV0a0mJo+ugAfEEOxeFnbCaUbYYVzMcuErs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765027210; c=relaxed/simple; bh=NCDZRGh4CNEjF8wzrz0/qmUmjmi/vLJ1iChHLMKHngw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=S0B3NXQzxc6XfmGDZro6syeGC+P0vprzhtai/+ea29CX19DB/YH0nVJvNAIGIbELrHL0siHBkoQavR86LcivPbCaj/LAzVDigI7f0H8yTgCGTYRR6Wr7EkYfPbXTD5is5qpZnCvSXJ0RkkQHBOQNZLCjCfJUMhbQ7iWAKjaPpsw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=jewnXvFO; arc=none smtp.client-ip=209.85.128.50 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="jewnXvFO" Received: by mail-wm1-f50.google.com with SMTP id 5b1f17b1804b1-4779d47be12so27722225e9.2 for ; Sat, 06 Dec 2025 05:20:09 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1765027208; x=1765632008; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=ighOjyvrf0/Zx4X8xYQ5PxpLMHcY6lBYspK5VjpofZs=; b=jewnXvFOSxZOqQqLY6RDXurEg2VFNdetftR+yAypiDP3afMRikdffwxGbBBb07AmY8 wf+E5X4LJm/IaEGpg21vWhhlGMPVwUs68yrnG8B3juoyMiV5JgersSfi0ntjjt87+djm FMPwR71WSDCtaADuvyY8OwdPNqcHe1bZc878Kv+KXOzM69bZzkBQZKogmP9RF9RCeG72 sCHnc2clkadfzvUNlbBPc2C6U4+hirNcz1fhRnUU9QICDlifWf8dUjYzsfF1PoOwkwE3 ZvtJvAXNf286/XeKk8brILX7pps6iuXF2l7bNZl5A5wpDUnSt1jqQs3pyT7adZwKTPXi SIAw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1765027208; x=1765632008; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=ighOjyvrf0/Zx4X8xYQ5PxpLMHcY6lBYspK5VjpofZs=; b=GksVRi+FdkSGroHtyIRaRul2uVM3CJXKRNxgNnGOfQjMYMUFoEPvmiR3kynKbiFJTj CeCzR3UEl34HENJbdPHATwB9Y0/e9lfzqzRPfI9u4hiBazsDEzqDZrx8UzCcIDIWhLt6 zkW4ZMF6RfkW8lRhwAGxpcSztasMH4USWIRJbh66I2htIIcFooHyD6ype4pDoMkQ4tCA NuJxsD/pCZOSpp18nZebiVerTRlP9M/TEx/iwjowR7bL2o6ZZFniADc1Qyx6lhzvQLcl ghax8ZhOD1JkaropAprRiAuM+vYYJk3ybNU0gdN7K7LLssPly6Ek5IcBv5UM++ay2S9M 5KwA== X-Forwarded-Encrypted: i=1; AJvYcCVUZIAhFQk9Wtc04CZ2YtANWDAZKDV9+/DBj81faK1gKeqac7UAY2OL7uw52qgyWfRdvgbYt7B6rpdHUrE=@vger.kernel.org X-Gm-Message-State: AOJu0YzGhszJNrsE4rL0D2invCLAHC+MRiCoH1uGixmYDLezWzF3hFEq VEm9fYJYWw5hmra1dd5us7EbXYg74wAkstawpKTk69z8AtITAmcqBD6K X-Gm-Gg: ASbGncuKpmvwhqFVnvxuLmiK127whjUv7FoB/ConM9e2YDfblBNCHFRkgbs4vcc97Ug DtSVSseXb3dyV1Neq/O1zb1JJDTzgUlyfSOR5BlA0/Q81nTxWIh6lQ6ptQEsYcBcH34Vd2skHta 49iklEJXdbypYRq5A+MVbv+EkFEkO66I2YGuhGFr3j47OtdODTMZPqjjjt5ywNFWCE1cltelRE5 3HxmQ2q2ibXQkXXOeFDHVjmavJY/h8lKzFwmDIYmsFacuVwWiGp7D5K6x7EgYaMzRK/bBnXvkhj unz+kQHnNRW3hbR/WScnJ1HCGuCIO14Kwn/SUr7N5yYOcGl4TzN1OnQrm762GBSRk1n8gngcbnb iwDr1ycw1f6HDcdki0ZyOJ19N33FUBr2y8xCd+coLNS8NRSOJ9SLyk4JjurpPI1+uRFXcPtCRSx lwCWsJhWdu+RTavDKTKdDHIUuwOZHPKtPg04qjemDUdTBTsgyWcUIQ/1BtbTI= X-Google-Smtp-Source: AGHT+IHsXFGHl8BMLHmt/CCXkj8VSf9vxbQIzflnN1FtUZfTdYecOi8VMSgUq5TzcBRzQ7yxWSFUew== X-Received: by 2002:a05:600c:3b99:b0:477:93f7:bbc5 with SMTP id 5b1f17b1804b1-47939dfa082mr27910485e9.10.1765027207289; Sat, 06 Dec 2025 05:20:07 -0800 (PST) Received: from f.. (cst-prg-14-82.cust.vodafone.cz. [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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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_commo= n_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_operatio= ns; * @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; --=20 2.48.1