[PATCH] xfs: avoid direct I/O write vs buffered I/O race

[Alex Elder]

On Sat, 2011-08-27 at 10:42 -0400, Christoph Hellwig wrote:
> Currently a buffered reader or writer can add pages to the pagecache
> while we are waiting for the iolock in xfs_file_dio_aio_write.  Prevent
> this by re-checking mapping->nrpages after we got the iolock, and if
> nessecary upgrade the lock to exclusive mode.  To simplify this a bit
> only take the ilock inside of xfs_file_aio_write_checks.
> 
> Signed-off-by: Christoph Hellwig <hch at lst.de>

I agree with Dave, moving the ILOCK acquisition into
xfs_file_aio_write_checks() is very nice.

In any case the core change looks good.

Reviewed-by: Alex Elder <aelder at sgi.com>