Re: O_DIRECT fails in some kernel and FS

[Chris Wedgwood]

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