From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f180.google.com (mail-pl1-f180.google.com [209.85.214.180]) (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 D76E4BA45 for ; Wed, 16 Oct 2024 07:33:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.180 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729064030; cv=none; b=rZHXavBi/eTtKD6iJlghjOxCZduy9gNavmIJkglqr2PkEVTvEX4hfj268v8O1N+5gbp0QWCkVSN8kLmA0QBL/aNr9t0YBXEKbUzgK0wEpQqXB017cQXyPRWqfXDoAnkUMY1Lu0taqbvdkkYMdXsCu3FCrKHTIsWfoHAN9HC8+FM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729064030; c=relaxed/simple; bh=feYTSeVka7QJWWBhSEjcTj4+tcS2XGrp6PYYQaXDwEE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=F2zu1opA2gf1bAkeD6DvFy5nn6vF5bbzldJGHjoQULzNdtBbCTvZ9D2K2n3ynU3JRqgf05iF1G8oobW0HJMbSGvcK9aIjuHezlm9e6+fd0ZA6nHsBzJV8ms1lGQ0GR3Ta4AFyF7kd+t4gO02N3YmnrijsPwhRUO/KBMWN9T5urE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=bytedance.com; spf=pass smtp.mailfrom=bytedance.com; dkim=pass (2048-bit key) header.d=bytedance.com header.i=@bytedance.com header.b=NI7eGuDg; arc=none smtp.client-ip=209.85.214.180 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=bytedance.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bytedance.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bytedance.com header.i=@bytedance.com header.b="NI7eGuDg" Received: by mail-pl1-f180.google.com with SMTP id d9443c01a7336-20c8b557f91so51782955ad.2 for ; Wed, 16 Oct 2024 00:33:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance.com; s=google; t=1729064028; x=1729668828; 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=thSSg5ShR5xJz6ZGwKGRw0pVZLjhIQAJQj0YRSu6SgM=; b=NI7eGuDgIpgpxl/NitGvuj2Pcym/7vmB/cEO3dmUE0Z6xcodFY9UfkL2g7nzTdEsJy xH7cYb25EGN2XXqDvaG2MtTj/02O7v46TZ4qXCcp4f9Iv4iaq7yjUtiM9+kUSN8RJsQG EKpFPzCdPcG3dcGf++ibpxQWj8+X0JxtXApAxrZpTfN4sZwVETEP+YS73jjriGJshmUX n4woQp1Ikx2/fgS/6RnRNmd6VEZDCUYKK9yPkhJO167eOZPWY59zkcLIRu8TA5n4k5v3 zz8e7Dvlq7Z7B7er2Vj1gV7iD6qnEcAYgG+ZzRxzl9EZ2vtV8NqOlDt2Sdt1omY9zm5L G0CQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1729064028; x=1729668828; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=thSSg5ShR5xJz6ZGwKGRw0pVZLjhIQAJQj0YRSu6SgM=; b=qG6Z8/klD80gb+bnVBmEEgO0akhnPzJA+qcXsjXoAtcZl7Av26uLJD20z82XjYAG1z 4PM9/3OGatJQwpJp4alkEv07u/uPh+CFinDbPiP7KiqLm0rAU/e2z1epsSOJ1LOeB3WB tTx3we9o3B5knsHwDy5BR2VIs8V7B2IhlXlZK/VmHUex6W3+gpe738ZQab/Nm6cHAFn+ /cuxtjhOkMLkpbt0cm9l5X8A87nhJNdO2ON9/++4840PAfoLyt3lWJHyzkSt9CNq6xgk mtF1Eq7g5HySj0NpueKA+a3AH0Wh5J93R0YeNPvIAPwx6NPJASzE3iAcgVRBO7gljXVA EADg== X-Forwarded-Encrypted: i=1; AJvYcCXc7cUSb3J/CzyMOXLVB52pA1GMmGjHF1VAxvlJ7CAUAgK3i6h5YtCVZTu4IAv6/3OKCFAF2jDSKIDPbzo=@vger.kernel.org X-Gm-Message-State: AOJu0YxFsMuesNp0eGPSBj5GfCCeeXVwYbqH1LCRhW/CQH1wtWse+rT4 wtxSeh0zoE/rBA+4J4rMc83/rkLI14mH2Kq2cuJVf2fOJVLxRAPPOEVVUOd4pJY= X-Google-Smtp-Source: AGHT+IFVld/ABfC+a47ultviWqV/D/tDl2m5qap0Aw12fa9OnUPwgfuOk2l77mPB3egySl0roAs9gg== X-Received: by 2002:a17:903:189:b0:20c:fb47:5c05 with SMTP id d9443c01a7336-20d27f26c4emr47690995ad.46.1729064028119; Wed, 16 Oct 2024 00:33:48 -0700 (PDT) Received: from GQ6QX3JCW2.bytedance.net ([203.208.189.7]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-20d1804c698sm23342265ad.187.2024.10.16.00.33.44 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Wed, 16 Oct 2024 00:33:47 -0700 (PDT) From: lizhe.67@bytedance.com To: hch@infradead.org Cc: akpm@linux-foundation.org, boqun.feng@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lizhe.67@bytedance.com, longman@redhat.com, mingo@redhat.com, peterz@infradead.org, will@kernel.org Subject: Re: [RFC 1/2] rwsem: introduce upgrade_read interface Date: Wed, 16 Oct 2024 15:33:40 +0800 Message-ID: <20241016073340.42565-1-lizhe.67@bytedance.com> X-Mailer: git-send-email 2.45.2 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Tue, 15 Oct 2024 21:56:51 -0700, hch@infradead.org wrote: >On Wed, Oct 16, 2024 at 12:35:59PM +0800, lizhe.67@bytedance.com wrote: >> From: Li Zhe >> >> Introduce a new rwsem interface upgrade_read(). We can call it > >It's obviously a try_upgrade_read, right? Yes, try_upgrade_read is a better name, I will fix it in v2. Thanks! > >> +extern int upgrade_read(struct rw_semaphore *sem); > >No need for the extern. Also please make any new advanced funtionality Sorry I don't understand why extern is not needed. If we remove it, we will encounter the following compilation error: mm/khugepaged.c:1145:6: error: implicit declaration of function 'upgrade_read'; did you mean 'i_gid_read'? [-Werror=implicit-function-declaration] if (upgrade_read(&mm->mmap_lock)) { ^~~~~~~~~~~~ >like this an EXPORT_SYMBO_GPL. That is if you actually had a modular >user, the current one is built-in. (although we could use this in >XFS if it lands). I see all advanced functionality in kernel/locking/rwsem.c is tagged with EXPORT_SYMBOL (which is used in my patch), and I'm not sure if I need to change it to EXPORT_SYMBO_GPL. Hope to see this interface used by XFS.