Date: Mon, 06 Oct 2003 23:55:17 +0200 From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> To: Garrett Wollman <wollman@khavrinen.lcs.mit.edu> Cc: arch@FreeBSD.org Subject: Re: Alignment of disk-I/O from userland. Message-ID: <26369.1065477317@critter.freebsd.dk> In-Reply-To: Your message of "Mon, 06 Oct 2003 17:46:51 EDT." <200310062146.h96Lkpx0093486@khavrinen.lcs.mit.edu>
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In message <200310062146.h96Lkpx0093486@khavrinen.lcs.mit.edu>, Garrett Wollman writes: >I think that gives us plenary authority to require appropriate >alignment of data buffers used to access disk devices directly. Well, apart from us wedging or botching the request rather than return a consistent error we're standards compliant then. It has been mentioned on #thatchannel that busdma should take care of this by copying the request as necessary. Faced with the prospect of a request several megabytes in size, I don't like the prospect of malloc/bcopy too much. All in all, I would advocate that we decide that disks in FreeBSD are allowed to return ENXIO if they get insufficiently aligned requests. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.
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