linux-ext4 - Re: [PATCH v5 7/9] iomap/xfs: Eliminate the iomap

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Date:   Sun, 8 Jan 2023 09:32:38 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     "Darrick J. Wong" <djwong@...nel.org>,
        Andreas Gruenbacher <agruenba@...hat.com>,
        Christoph Hellwig <hch@...radead.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-ext4@...r.kernel.org, cluster-devel@...hat.com
Subject: Re: [PATCH v5 7/9] iomap/xfs: Eliminate the iomap_valid handler

On Wed, Jan 04, 2023 at 07:08:17PM +0000, Matthew Wilcox wrote:
> On Wed, Jan 04, 2023 at 09:53:17AM -0800, Darrick J. Wong wrote:
> > I wonder if this should be reworked a bit to reduce indenting:
> > 
> > 	if (PTR_ERR(folio) == -ESTALE) {
> 
> FYI this is a bad habit to be in.  The compiler can optimise
> 
> 	if (folio == ERR_PTR(-ESTALE))
> 
> better than it can optimise the other way around.

Yes.  I think doing the recording that Darrick suggested combined
with this style would be best:

	if (folio == ERR_PTR(-ESTALE)) {
		iter->iomap.flags |= IOMAP_F_STALE;
		return 0;
	}
	if (IS_ERR(folio))
		return PTR_ERR(folio);