Re: notes on volatile write caches vs fdatasync

From: Jeff Garzik
Date: Thu Aug 27 2009 - 15:26:43 EST

On 08/27/2009 02:49 PM, Christoph Hellwig wrote:
On Thu, Aug 27, 2009 at 03:02:52PM +0200, Jan Kara wrote:
I've noticed this as well when we were tracking some problems Pavel
Machek found with his USB stick. I even wrote a patch at the time
but it somehow died out. Now, the situation should be simpler with
fsync paths cleaned up... BTW: People wanted this to be configurable per
block device which probably makes sence...

Yeah, that patch is pretty ugly. We need to do these cache flushes
in ->fsync (and ->sync_fs if any filesystem really doesn't guarantee to
issue transaction there after data has been written). Adding it
to simple_fsync too sounds good to me.

Agreed. That was the direction I was heading with my patch[1]. Last feedback I got on that was needing to add a knob to optionally disable this new cache-flush behavior.


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