On Fri, Feb 26, 2021 at 10:32:50AM +1100, Stephen Rothwell wrote:
> > > - return filemap_read(iocb, to, ret);
> > > + if (iocb->ki_flags & IOCB_NOWAIT)
> > > + iocb->ki_flags |= IOCB_NOIO;
> > > +
> > > - ret = generic_file_buffered_read(iocb, to, ret);
> > > ++ ret = filemap_read(iocb, to, ret);
> > > +
> > > + if (iocb->ki_flags & IOCB_NOWAIT) {
> > > + iocb->ki_flags &= ~IOCB_NOIO;
> > > + if (ret == 0)
> > > + ret = -EAGAIN;
> > > + }
> > > +
> > > + return ret;
> > > }
I think the above code looks completely bogus. Instead whatever code
in btrfs hecks for IOCB_NOIO to avoid blocking readahead should also
check IOCB_NOWAIT.
