Re: Alignment of disk-I/O from userland.

From: Poul-Henning Kamp (phk_at_phk.freebsd.dk)
Date: 10/06/03

  • Next message: Mark Valentine: "Re: Alignment of disk-I/O from userland." 
    To: Garrett Wollman <wollman@khavrinen.lcs.mit.edu>
Date: Mon, 06 Oct 2003 23:55:17 +0200

    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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  • Next message: Mark Valentine: "Re: Alignment of disk-I/O from userland."