From: Matthew Wilcox <willy@infradead.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: Andreas Gruenbacher <agruenba@redhat.com>,
Dave Chinner <dchinner@redhat.com>,
"Darrick J . Wong" <djwong@kernel.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-ext4@vger.kernel.org, cluster-devel@redhat.com,
Christoph Hellwig <hch@lst.de>
Subject: Re: [RFC v6 04/10] iomap: Add iomap_get_folio helper
Date: Tue, 10 Jan 2023 13:34:16 +0000 [thread overview]
Message-ID: <Y71pWJ0JHwGrJ/iv@casper.infradead.org> (raw)
In-Reply-To: <Y70l9ZZXpERjPqFT@infradead.org>
On Tue, Jan 10, 2023 at 12:46:45AM -0800, Christoph Hellwig wrote:
> On Mon, Jan 09, 2023 at 01:46:42PM +0100, Andreas Gruenbacher wrote:
> > We can handle that by adding a new IOMAP_NOCREATE iterator flag and
> > checking for that in iomap_get_folio(). Your patch then turns into
> > the below.
>
> Exactly. And as I already pointed out in reply to Dave's original
> patch what we really should be doing is returning an ERR_PTR from
> __filemap_get_folio instead of reverse-engineering the expected
> error code.
Ouch, we have a nasty problem.
If somebody passes FGP_ENTRY, we can return a shadow entry. And the
encodings for shadow entries overlap with the encodings for ERR_PTR,
meaning that some shadow entries will look like errors. The way I
solved this in the XArray code is by shifting the error values by
two bits and encoding errors as XA_ERROR(-ENOMEM) (for example).
I don't _object_ to introducing XA_ERROR() / xa_err() into the VFS,
but so far we haven't, and I'd like to make that decision intentionally.
next prev parent reply other threads:[~2023-01-10 13:35 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-08 19:40 [RFC v6 00/10] Turn iomap_page_ops into iomap_folio_ops Andreas Gruenbacher
2023-01-08 19:40 ` [RFC v6 01/10] iomap: Add __iomap_put_folio helper Andreas Gruenbacher
2023-01-08 19:40 ` [RFC v6 02/10] iomap/gfs2: Unlock and put folio in page_done handler Andreas Gruenbacher
2023-01-08 19:40 ` [RFC v6 03/10] iomap: Rename page_done handler to put_folio Andreas Gruenbacher
2023-01-08 19:40 ` [RFC v6 04/10] iomap: Add iomap_get_folio helper Andreas Gruenbacher
2023-01-08 21:33 ` Dave Chinner
2023-01-09 12:46 ` Andreas Gruenbacher
2023-01-10 8:46 ` Christoph Hellwig
2023-01-10 9:07 ` Andreas Grünbacher
2023-01-10 13:34 ` Matthew Wilcox [this message]
2023-01-10 15:24 ` Christoph Hellwig
2023-01-11 19:36 ` Matthew Wilcox
2023-01-11 20:52 ` Dave Chinner
2023-01-12 8:41 ` Christoph Hellwig
2023-01-15 17:01 ` Darrick J. Wong
2023-01-15 17:06 ` Darrick J. Wong
2023-01-16 5:46 ` Matthew Wilcox
2023-01-16 7:34 ` Christoph Hellwig
2023-01-16 13:18 ` Matthew Wilcox
2023-01-16 16:02 ` Christoph Hellwig
2023-01-08 19:40 ` [RFC v6 05/10] iomap/gfs2: Get page in page_prepare handler Andreas Gruenbacher
2023-01-31 19:37 ` Matthew Wilcox
2023-01-31 21:33 ` Andreas Gruenbacher
2023-01-08 19:40 ` [RFC v6 06/10] iomap: Add __iomap_get_folio helper Andreas Gruenbacher
2023-01-10 8:48 ` Christoph Hellwig
2023-01-08 19:40 ` [RFC v6 07/10] iomap: Rename page_prepare handler to get_folio Andreas Gruenbacher
2023-01-08 19:40 ` [RFC v6 08/10] iomap/xfs: Eliminate the iomap_valid handler Andreas Gruenbacher
2023-01-08 21:59 ` Dave Chinner
2023-01-09 18:45 ` Andreas Gruenbacher
2023-01-09 22:54 ` Dave Chinner
2023-01-10 1:09 ` Andreas Grünbacher
2023-01-15 17:29 ` Darrick J. Wong
2023-01-18 7:21 ` Christoph Hellwig
2023-01-18 9:11 ` Damien Le Moal
2023-01-18 19:04 ` Darrick J. Wong
2023-01-18 19:57 ` Andreas Grünbacher
2023-01-18 21:42 ` Dave Chinner
2023-01-10 8:51 ` Christoph Hellwig
2023-01-10 8:52 ` Christoph Hellwig
2023-01-08 19:40 ` [RFC v6 09/10] iomap: Rename page_ops to folio_ops Andreas Gruenbacher
2023-01-08 19:40 ` [RFC v6 10/10] xfs: Make xfs_iomap_folio_ops static Andreas Gruenbacher
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