Re: [PATCH 1/3] fs: allow short direct-io reads to be completedvia buffered IO V2

[Christoph Hellwig]

On Thu, May 06, 2010 at 03:00:13PM -0400, Josef Bacik wrote:
> V1->V2: Check to see if our current ppos is >= i_size after a short DIO read,
> just in case it was actually a short read and we need to just return.
> 
> This is similar to what already happens in the write case.  If we have a short
> read while doing O_DIRECT, instead of just returning, fallthrough and try to
> read the rest via buffered IO.  BTRFS needs this because if we encounter a
> compressed or inline extent during DIO, we need to fallback on buffered.  If the
> extent is compressed we need to read the entire thing into memory and
> de-compress it into the users pages.  I have tested this with fsx and everything
> works great.  Thanks,

This seems safe to me, but I'm a bit worried about potential breakages.
Did you test this with xfsqa on xfs and ext3/4 to make sure there are
no regressions?

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