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List:       freebsd-hackers
Subject:    Re: BIO_FLUSH and ips(4)
From:       Xin LI <delphij () gmail ! com>
Date:       2010-04-25 5:39:26
Message-ID: x2la78074951004242239n6471060dj24d8d71c5a41f406 () mail ! gmail ! com
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Hi,

On Sat, Apr 24, 2010 at 8:20 PM, YONETANI Tomokazu <qhwt+fbsd@les.ath.cx> wrote:
> Hello.
>
> The ServeRAID driver, or ips(4), seems to distinguish read or write requests
> with a macro called ips_read_request(), which is defined as
>
>  #define ips_read_request(iobuf)               ((iobuf)->bio_cmd == BIO_READ)
>
> in its strategy routine and a few other places.  So when the request is
> BIO_FLUSH, the ips driver issues a write command (IPS_WRITE_CMD) with
> length == 0, right?
>
> My question is, do ServeRAID controllers treat 0-byte write command
> as a sync-to-disk request, or is there any command for that purpose?
> There's a command called IPS_CACHE_FLUSH_CMD defined in ipsreg.h,
> but it's not used anywhere in the normal code path.

It seems Linux driver is using it (on shutdown/reset) but I'm not sure
if this would have some side effect, etc.?

Cheers,
-- 
Xin LI <delphij@delphij.net> http://www.delphij.net
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