On Sun, Sep 30, 2012 at 05:58:11AM +0000, Nicholas A. Bellinger wrote:
> From: Nicholas Bellinger <n...@linux-iscsi.org>
>
> 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.
> + /*
Indention error.
> + * Optionally allow fd_buffered_io=1 to be enabled for people
> + * who know what they are doing w/o O_DSYNC.
> + */
This comment doesn't explain at all what's going on here. It should be
something like
/*
* Unsafe mode allows disabling data integrity by not forcing
* data out to disk in writethrough cache mode. Only to be used
* for benchmark cheating or similar purposes.
*/
> #define FBDF_HAS_PATH 0x01
> #define FBDF_HAS_SIZE 0x02
> +#define FDBD_USE_BUFFERED_IO 0x04
This should be named BDBD_UNSAFE
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