From mboxrd@z Thu Jan  1 00:00:00 1970
From: Chris Friesen <chris.friesen@genband.com>
Subject: Re: [sqlite] light weight write barriers
Date: Thu, 15 Nov 2012 16:35:47 -0600
Message-ID: <50A56E43.3040805@genband.com>
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Cc: General Discussion of SQLite Database <sqlite-users@sqlite.org>,
	Vladislav Bolkhovitin <vst@vlnb.net>,
	Nico Williams <nico@cryptonector.com>,
	linux-fsdevel@vger.kernel.org, Theodore Ts'o <tytso@mit.edu>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Richard Hipp <drh@hwaci.com>
To: Ryan Johnson <ryan.johnson@cs.utoronto.ca>
Return-path: <linux-kernel-owner@vger.kernel.org>
In-Reply-To: <50A52133.9050204@cs.utoronto.ca>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: linux-fsdevel.vger.kernel.org

On 11/15/2012 11:06 AM, Ryan Johnson wrote:

> The easiest way to implement this fsync would involve three things:
> 1. Schedule writes for all dirty pages in the fs cache that belong to
> the affected file, wait for the device to report success, issue a cache
> flush to the device (or request ordering commands, if available) to make
> it tell the truth, and wait for the device to report success. AFAIK this
> already happens, but without taking advantage of any request ordering
> commands.
> 2. The requesting thread returns as soon as the kernel has identified
> all data that will be written back. This is new, but pretty similar to
> what AIO already does.
> 3. No write is allowed to enqueue any requests at the device that
> involve the same file, until all outstanding fsync complete [3]. This is
> new.

This sounds interesting as a way to expose some useful semantics to 
userspace.

I assume we'd need to come up with a new syscall or something since it 
doesn't match the behaviour of posix fsync().

Chris