[PATCH 21/25] xfs: add buffer pre-write callback

[Phil White]

On Thu, Oct 25, 2012 at 05:34:10PM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner at redhat.com>
> 
> Add a callback to the buffer write path to enable verification of
> the buffer and CRC calculation prior to issuing the write to the
> underlying storage.
> 
> If the callback function detects some kind of failure or error
> condition, it must mark the buffer with an error so that the caller
> can take appropriate action. In the case of xfs_buf_ioapply(), a
> corrupt metadta buffer willt rigger a shutdown of the filesystem,
> because something is clearly wrong and we can't allow corrupt
> metadata to be written to disk.
> 
> Signed-off-by: Dave Chinner <dchinner at redhat.com>

Reviewed-by: Phil White <pwhite at sgi.com>