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Date:      Wed, 7 Nov 2018 13:31:38 -0700
From:      Warner Losh <imp@bsdimp.com>
To:        Poul-Henning Kamp <phk@phk.freebsd.dk>
Cc:        "Rodney W. Grimes" <rgrimes@freebsd.org>, Ian Lepore <ian@freebsd.org>,  Maxim Sobolev <sobomax@freebsd.org>, src-committers <src-committers@freebsd.org>,  svn-src-all@freebsd.org, svn-src-head@freebsd.org,  Pawel Jakub Dawidek <pjd@freebsd.org>
Subject:   Re: svn commit: r340187 - head/sys/geom
Message-ID:  <CANCZdfr0gvfoeDfQu5L0QuGV8L%2BfJeQ=HQiWeaQuosP5fw3YyQ@mail.gmail.com>
In-Reply-To: <1603.1541622015@critter.freebsd.dk>
References:  <1541606248.52306.42.camel@freebsd.org> <201811071606.wA7G6mQW001639@pdx.rh.CN85.dnsmgr.net> <CANCZdfrK-7vBETkhfQ9KkM4usrvjVh8wS_OZJiDmH5336DTsqQ@mail.gmail.com> <1603.1541622015@critter.freebsd.dk>

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On Wed, Nov 7, 2018 at 1:20 PM Poul-Henning Kamp <phk@phk.freebsd.dk> wrote:

> --------
> In message <
> CANCZdfrK-7vBETkhfQ9KkM4usrvjVh8wS_OZJiDmH5336DTsqQ@mail.gmail.com>
> , Warner Losh writes:
>
> >BIO_FLUSH is primarily done to force ordering points,
>
> Originally BIO_FLUSH was defined the way it is, to make it possible
> to flush an isolated specified range on providers which support that
> so that fsync(2) could be implemented that way.
>
> I can't remember the exact semantics of the two "magic" flush
> operations (off=0,len=0) and (off=end,len=0) but they were different
> from each other in some important aspect (Pawel?)
>

I couldn't find any place where the different types of flush are
differentiated (nothing in CAM for sure), though I suppose I could have
missed something. All the CAM drivers just use it to push data to the
device and don't look at the flags.

Warner


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