From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pg1-f171.google.com (mail-pg1-f171.google.com [209.85.215.171]) (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 B7B1A84024 for ; Thu, 1 Feb 2024 17:38:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.171 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706809086; cv=none; b=Gl9YhWYZl6Kg4ZmBwVhrfGowA3K5XCp490zteEFgEkRuKbb6Rd262eQ39yXan5GQgH4v4W+wY87/715tAPRWQ+QtA6zR92ZvMHkNrd/FnBqBN8N85x+QZeEOzbNT41zEGL3oGIRK4BJetomI74icrwiKbLdinPTnoxg9BwaKgng= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706809086; c=relaxed/simple; bh=F6aEyGx8n2KD1Dc+SF07MuC9HJNGbCCubSaI49hxeTU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=XVoJJuCMhhD/J+WAyxuaPwEuIjW2OoGy7ogmCSI3/Rv329ffrUgv78UVDF5qIQVuFd/was416WrNh47h7JdPmQ2mbkK5+LNT8fVEhGVp3z20YtHDOoo0SqZVocKqcQf5VMjGyZ38cGveRdm6BQVvbFgwfREpCCa02VsWW5QzOJ4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=acm.org; spf=pass smtp.mailfrom=gmail.com; arc=none smtp.client-ip=209.85.215.171 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=acm.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Received: by mail-pg1-f171.google.com with SMTP id 41be03b00d2f7-53fbf2c42bfso963165a12.3 for ; Thu, 01 Feb 2024 09:38:04 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1706809084; x=1707413884; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=0gw83YyakVHHUi2A5N9A7N9A49UYycmoToICzHtmT4o=; b=I8BxEdR0I33F3jtQXA3XyLO/mdGTSMHkHmJAvhCXm7wkPEXk2Fm7FShONCwaa9nPsX rN65QRYbQuHc6vD3qax8TzR6rodFs8PK3T5YzRD6K+e67pn2ao+dBJ9B20wh1dCOtuJY gvaVDZPEcvmGY3LrsHdHDX1OqUVvk034gyn4+N1DjQ121Hqu9yNsM1yl886umtyy/IPc 4hkQvg2+nAZBIXTYrpA3g7VH+nR+1AM3iWJebbI3vrJ6OOA31fsckQHRe6VnEUftOoPJ CmYEkiVZBbDB+dlPAYBDjP0EZ7YFtM9i/1L3vqymO/zJ71H/BHbyMDyG5HU5KT0/h9gb J+gg== X-Gm-Message-State: AOJu0Yxzf9Tq1o0mtUaiaidgTREBeWELRpQvn1+52YJq9+Y4PhL205iD Fh4iRijPUw6crqyfH3pV2FRd90RYYNoXw1g5w9ZEMLA5B7V9p2bi X-Google-Smtp-Source: AGHT+IELnjmzwRGy9RhratFzwYzzql1bfvD+AZLk+FDhP7YT5eSpgHFfpmZV/fljE+Ym/HpRleSQFQ== X-Received: by 2002:a05:6a21:3984:b0:19e:4816:e71a with SMTP id ad4-20020a056a21398400b0019e4816e71amr1464965pzc.27.1706809083920; Thu, 01 Feb 2024 09:38:03 -0800 (PST) X-Forwarded-Encrypted: i=0; AJvYcCXMiBB7pw4sQLlt9cMv+cvmShsgApSOhCrj4f/X8ZpKVHPI+W/xuOxNdGLYxXyZ9CcnKN6zwC6nfuO68m8zm1kwduqJ975K16A7RYJmNh7a/FLiUqkM/IgGXgGZKgI4rV0P3VZG8eH0DF3LvIcKdsuNRJLTVRuvEMjWIlz/kr9fcveOKSCTDMv3HEokeMmSu5PS5y0dbxF6+5137w5NywDIABtSrAeIg4hiyg2Fr8uIQlgs6B/1NmyhZnqJOB8S4zIxdvxdRQUEANY3q4S14Osmv7BwLV73pacUTlq6HNZrjI0IgEBUEah0W5lQdIdnbd6dKU100A0= Received: from ?IPV6:2620:0:1000:8411:170e:a1a5:1887:adb2? ([2620:0:1000:8411:170e:a1a5:1887:adb2]) by smtp.gmail.com with ESMTPSA id i17-20020aa78b51000000b006d98ae070c3sm2548pfd.135.2024.02.01.09.38.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 01 Feb 2024 09:38:03 -0800 (PST) Message-ID: Date: Thu, 1 Feb 2024 09:38:02 -0800 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 3/6] fs: Split fcntl_rw_hint() Content-Language: en-US To: Dave Chinner Cc: Christian Brauner , Alexander Viro , linux-fsdevel@vger.kernel.org, Jens Axboe , Christoph Hellwig , "Martin K . Petersen" , Kanchan Joshi , Jeff Layton , Chuck Lever , Stephen Rothwell References: <20240131205237.3540210-1-bvanassche@acm.org> <20240131205237.3540210-4-bvanassche@acm.org> From: Bart Van Assche In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 1/31/24 13:07, Dave Chinner wrote: > On Wed, Jan 31, 2024 at 12:52:34PM -0800, Bart Van Assche wrote: >> + inode_lock(inode); >> + inode->i_write_hint = hint; >> + inode_unlock(inode); > > What is this locking serialising against? The inode may or may not > be locked when we access this in IO path, so why isn't this just > WRITE_ONCE() here and READ_ONCE() in the IO paths? How about using WRITE_ONCE()/READ_ONCE() in the fcntl implementations and regular reads in the I/O paths? Using F_SET_RW_HINT while I/O is ongoing is racy - there are no guarantees about how F_SET_RW_HINT will affect I/O that has already been submitted. Hence, I think that it is acceptable to use regular reads for i_write_hint in the I/O paths. Thanks, Bart.