Christoph Hellwig, on 10/01/2012 04:46 AM wrote:
On Sun, Sep 30, 2012 at 05:58:11AM +0000, Nicholas A. Bellinger wrote:
From: Nicholas Bellinger<nab@xxxxxxxxxxxxxxx>
This patch re-adds the ability to optionally run in buffered FILEIO mode
(eg: w/o O_DSYNC) for device backends in order to once again use the
Linux buffered cache as a write-back storage mechanism.
This difference with this patch is that fd_create_virtdevice() now
forces the explicit setting of emulate_write_cache=1 when buffered FILEIO
operation has been enabled.
What this lacks is a clear reason why you would enable this inherently
unsafe mode. While there is some clear precedence to allow people doing
stupid thing I'd least like a rationale for it, and it being documented
as unsafe.
Nowadays nearly all serious applications are transactional, and know how to flush
storage cache between transactions. That means that write back caching is
absolutely safe for them. No data can't be lost in any circumstances.
Welcome to the 21 century, Christoph!
Vlad
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