Date: Mon, 6 Oct 2003 17:53:28 -0700 From: Sam Leffler <sam@errno.com> To: "Poul-Henning Kamp" <phk@phk.freebsd.dk>, Scott Long <scottl@freebsd.org> Cc: arch@freebsd.org Subject: Re: Alignment of disk-I/O from userland. Message-ID: <200310061753.28562.sam@errno.com> In-Reply-To: <27374.1065481871@critter.freebsd.dk> References: <27374.1065481871@critter.freebsd.dk>
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On Monday 06 October 2003 04:11 pm, Poul-Henning Kamp wrote: > In message <20031006163218.L55190@pooker.samsco.home>, Scott Long writes: ...stuff deleted... > >As for returning an error code for a buffer that we (arbitrarily) believe > >to be too big to align, [...] > > I have never advocated returning an error based on "alignment and size", > only based on alignment alone. Imposing this restriction is a major semantic change that I consider a very bad idea. You are basically imposing the semantics of O_DIRECT on all i/o operations going to a device. I think it is important to give best effort to support unaligned operations `by default. I can imagine restricting this to some upper size bound but existing applications, regardless of how well you consider them to be written, must continue to work. Sam
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