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Date: Sun, 3 Feb 2002 06:09:26 -0800
From: Chris Wedgwood <cw@f00f.org>
To: Stephen Lord <lord@sgi.com>
Cc: Jeff Garzik <garzik@havoc.gtf.org>, Chris Mason <mason@suse.com>,
        Andrea Arcangeli <andrea@suse.de>, Andrew Morton <akpm@zip.com.au>,
        Ricardo Galli <gallir@uib.es>,
        Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: O_DIRECT fails in some kernel and FS
Message-ID: <20020203140926.GA14532@tapu.f00f.org>
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On Sun, Feb 03, 2002 at 07:40:57AM -0600, Stephen Lord wrote:

    What we had were two flags, one which indicated use direct I/O,
    and another which indicated return an error to user space rather
    than go through buffers.  So lie to me and make it work, or don't
    lie to me options I suppose.

This seems way to complex in the case of reiserfs... you're only going
to see tails for small files (typically under 16k) and for the tail
part when less than a block.

Since O_DIRECT much be blocked sized and block aligned, I'm not sure
if this is a problem at present...

    I suspect the reason XFS never did small files in the inode was
    because of the problems with implementing mmap and O_DIRECT.

How does IRIX deal with O_DIRECT read/writes of a mapped area?
Invalidate them or just accept things as being incoherent?


    --cw
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