linux-kernel - Re: linux-next: manual merge of the akpm-current tree with the btrfs tree

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Date:   Fri, 26 Feb 2021 06:16:26 +0100
From:   Christoph Hellwig <hch@....de>
To:     Stephen Rothwell <sfr@...b.auug.org.au>
Cc:     David Sterba <dsterba@...e.cz>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Hellwig <hch@....de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Next Mailing List <linux-next@...r.kernel.org>,
        Martin Raiber <martin@...ackup.org>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>
Subject: Re: linux-next: manual merge of the akpm-current tree with the
 btrfs tree

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.