From nobody Sun Feb 8 02:55:47 2026 Received: from mail-pf1-f181.google.com (mail-pf1-f181.google.com [209.85.210.181]) (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 3AC9E3E46D for ; Wed, 21 Feb 2024 09:10:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.181 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708506644; cv=none; b=ofQK3wk/6TawcV0ViVyyeoFpwCaXQqXOMD/se/h48263wV7UuCRgcE1za1NacdStHvbZvSdsgWqrCwKzAF0vaQd56zoSCSoy8lfOmnVT8t5xNJ8LxBS0fAyCnyBPR3I5bvYt7lD10SgJwjf3Af2nx6tk2FlCEzUv6M3gP+tPOwA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708506644; c=relaxed/simple; bh=iSAF8mw9yPYD+iDPeUrECkO4z2kAalTw8m6Jdp/05oo=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=RQcGC5hJ6pb5oRvWfP+x2KKjp1fAqJeuenHkcOJtPWdhDdkwJW0wpGGkr/7UwNb1AgSliFTE5cUPSQbriMr3KIqTT6xxiHG1lw/Fu6pGR1z5zJgoCtNoCoifUazzvc8iOuLLAXlNw6U+2XB8Dn4TeUlFAu+zcRZzyQn1DgrL7j0= 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=dop/TkNu; arc=none smtp.client-ip=209.85.210.181 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="dop/TkNu" Received: by mail-pf1-f181.google.com with SMTP id d2e1a72fcca58-6e4751b97eeso1734204b3a.1 for ; Wed, 21 Feb 2024 01:10:42 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1708506642; x=1709111442; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=AZrK/F617BnVPDrc38OOvpBVEVkH26jNk6vxgeNneU4=; b=dop/TkNuXchRwE0BX/jqUdui17Q0eknLzP4ndHUGFXbza1MNbv15+uuKHv+ab/AyXG sUzJ3XeKII3R6RM0eHrTjdY7s98zNamq9BDn3PXDAtfgI7vw5lIwa2qqaAqiqx86D/UH qbK9q6uCJAFfj42wYzts2NI7iicvX7pBRJiGHJHGdQ4O6r2Jt2HFDmxC2RQwvI6IfdHl l/nzLVKWMLLJsGKKFDIX0IFa3jnoqZfu3Rty2en2WTrAGUBX/zE/xtICD8Hlow8jnjt4 IOzZPsaJYrfWea9WlA6Kr0Ae6blgVnhprNbuB0d+NP5HSn/B/8Lw9njIEBih+wTibhgR OCQQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1708506642; x=1709111442; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=AZrK/F617BnVPDrc38OOvpBVEVkH26jNk6vxgeNneU4=; b=TB07xhwQZKXOtXoi2lt/O+wI9qcrVC8TLuXQ6Jpg9NkyXAn9EYlYSD1B7jreKCIZZA lH7YVmVrzf8OLpto1zjQ9i1geSAMnGkYi3xnDdyYj+koUDLyGku+v8RrFYHINtKVe/28 IttTRTiruXU8o6drT8OWw4IkrgiLXWgEdBf23pgTlc2x3QcfpoN1DCkHuPUrytCQg5Bn ePWVwWwigsHFaLupfSiWPV7TBNZXg4MloHsVSehSM/XFlU2P2orBg09aaOeojNhEZdjD YjxoJ2o4yRlF+ZoiAihYan0aCdByR6XeMY4HQeZNYSiyPfUu9nqB0dLl2vta6tdKZ610 wygA== X-Gm-Message-State: AOJu0Yz8idyQw8AU9G91I/RFHRUhppBL6/BMyg4OQGUf75w1LncH7IG5 mEEH/8ImNh4ZsejHoVD7h3Cpk56wiJApGG08mDlJwsU6rEUzzArqal9OVBSptj0= X-Google-Smtp-Source: AGHT+IGXZqxfiiMDC6vtnenG2qgZLaSI/0g1HeRJtxblZfh2W0gcZVCz8c+V7ui1oDCM/18JuK1pdw== X-Received: by 2002:a05:6a20:6f88:b0:1a0:64bc:743 with SMTP id gv8-20020a056a206f8800b001a064bc0743mr17634507pzb.7.1708506642497; Wed, 21 Feb 2024 01:10:42 -0800 (PST) Received: from barry-desktop.hub ([2407:7000:8942:5500:e5f3:9cc7:f0fb:8762]) by smtp.gmail.com with ESMTPSA id jk2-20020a170903330200b001da18699120sm7628159plb.43.2024.02.21.01.10.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 21 Feb 2024 01:10:42 -0800 (PST) From: Barry Song <21cnbao@gmail.com> To: akpm@linux-foundation.org, linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Barry Song Subject: [PATCH] mm/swapfile:__swap_duplicate: drop redundant WRITE_ONCE on swap_map for err cases Date: Wed, 21 Feb 2024 22:10:28 +1300 Message-Id: <20240221091028.123122-1-21cnbao@gmail.com> X-Mailer: git-send-email 2.34.1 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" From: Barry Song The code is quite hard to read, we are still writing swap_map after errors happen. Though the written value is as before, has_cache =3D count & SWAP_HAS_CACHE; count &=3D ~SWAP_HAS_CACHE; [snipped] WRITE_ONCE(p->swap_map[offset], count | has_cache); It would be better to entirely drop the WRITE_ONCE for both performance and readability. Signed-off-by: Barry Song --- mm/swapfile.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/swapfile.c b/mm/swapfile.c index 556ff7347d5f..17557003858c 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -3320,6 +3320,9 @@ static int __swap_duplicate(swp_entry_t entry, unsign= ed char usage) } else err =3D -ENOENT; /* unused swap entry */ =20 + if (err) + goto unlock_out; + WRITE_ONCE(p->swap_map[offset], count | has_cache); =20 unlock_out: --=20 2.34.1