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Message-ID: <Y6XDAG25Qumt/iyM@infradead.org>
Date: Fri, 23 Dec 2022 07:02:24 -0800
From: Christoph Hellwig <hch@...radead.org>
To: Andreas Gruenbacher <agruenba@...hat.com>
Cc: Christoph Hellwig <hch@...radead.org>,
"Darrick J . Wong" <djwong@...nel.org>,
Alexander Viro <viro@...iv.linux.org.uk>,
Matthew Wilcox <willy@...radead.org>,
linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-ext4@...r.kernel.org, cluster-devel@...hat.com
Subject: Re: [RFC v3 2/7] iomap: Add iomap_folio_done helper
On Fri, Dec 16, 2022 at 04:06:21PM +0100, Andreas Gruenbacher wrote:
> +static void iomap_folio_done(struct iomap_iter *iter, loff_t pos, size_t ret,
> + struct folio *folio)
> +{
> + const struct iomap_page_ops *page_ops = iter->iomap.page_ops;
> +
> + if (folio)
> + folio_unlock(folio);
> + if (page_ops && page_ops->page_done)
> + page_ops->page_done(iter->inode, pos, ret, &folio->page);
> + if (folio)
> + folio_put(folio);
> +}
How is the folio derefence going to work if folio is NULL?
That being said, I really wonder if the current API is the right way to
go. Can't we just have a ->get_folio method with the same signature as
__filemap_get_folio, and then do the __filemap_get_folio from the file
system and avoid the page/folio == NULL clean path entirely? Then on
the done side move the unlock and put into the done method as well.
> if (!folio) {
> status = (iter->flags & IOMAP_NOWAIT) ? -EAGAIN : -ENOMEM;
> - goto out_no_page;
> + iomap_folio_done(iter, pos, 0, NULL);
> + return status;
> }
>
> /*
> @@ -656,13 +670,9 @@ static int iomap_write_begin(struct iomap_iter *iter, loff_t pos,
> return 0;
>
> out_unlock:
> - folio_unlock(folio);
> - folio_put(folio);
> + iomap_folio_done(iter, pos, 0, folio);
> iomap_write_failed(iter->inode, pos, len);
>
> -out_no_page:
> - if (page_ops && page_ops->page_done)
> - page_ops->page_done(iter->inode, pos, 0, NULL);
> return status;
But for the current version I don't really understand why the error
unwinding changes here.
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