Jeff Moyer wrote:
> > Index: linux-2.6/mm/filemap.c
> > ===================================================================
> > --- linux-2.6.orig/mm/filemap.c 2008-10-03 11:21:31.000000000 +1000
> > +++ linux-2.6/mm/filemap.c 2008-10-03 12:00:17.000000000 +1000
> > @@ -1304,11 +1304,8 @@ generic_file_aio_read(struct kiocb *iocb
> > goto out; /* skip atime */
> > size = i_size_read(inode);
> > if (pos < size) {
> > - retval = filemap_write_and_wait(mapping);
> > - if (!retval) {
> > - retval = mapping->a_ops->direct_IO(READ, iocb,
> > + retval = mapping->a_ops->direct_IO(READ, iocb,
> > iov, pos, nr_segs);
> > - }
>
> So why is it safe to get rid of this? Can't this result in reading
> stale data from disk?
It seems that could be easily tested in one of the test suites, by
writing a page without O_DIRECT to make a dirty page, then reading the
same page with O_DIRECT. Do it a few times to be sure.
Do the test suites verify O_DIRECT / page-cache coherency?
Cheers,
-- Jamie
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