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Date: Fri, 3 Apr 2009 15:57:03 -0700
Message-ID: <72dbd3150904031557q33c5f29cr3b767131dcc2f51@mail.gmail.com>
Subject: Re: Linux 2.6.29
From: David Rees <drees76@gmail.com>
To: Janne Grunau <j@jannau.net>
Cc: Jeff Garzik <jeff@garzik.org>, Mark Lord <lkml@rtr.ca>,
       Lennart Sorensen <lsorense@csclub.uwaterloo.ca>,
       Jens Axboe <jens.axboe@oracle.com>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Ingo Molnar <mingo@elte.hu>, Andrew Morton <akpm@linux-foundation.org>,
       tytso@mit.edu, jesper@krogh.cc,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Fri, Apr 3, 2009 at 3:32 PM, Janne Grunau <j@jannau.net> wrote:
> On Fri, Apr 03, 2009 at 05:57:05PM -0400, Jeff Garzik wrote:
>> Just curious, does MythTV need fsync(), or merely to tell the kernel to
>> begin asynchronously writing data to storage?
>
> quoting the TheadedFileWriter comments
>
> /*
>  *   NOTE: This doesn't even try flush our queue of data.
>  *   This only ensures that data which has already been sent
>  *   to the kernel for this file is written to disk. This
>  *   means that if this backend is writing the data over a
>  *   network filesystem like NFS, then the data will be visible
>  *   to the NFS server after this is called. It is also useful
>  *   in preventing the kernel from buffering up so many writes
>  *   that they steal the CPU for a long time when the write
>  *   to disk actually occurs.
>  */

There is no need to fsync data on a NFS mount in Linux anymore.  All
NFS mounts are mounted sync by default now unless you explicitly
specify otherwise (and then you should then know what you're getting
in to).

-Dave