Re: [PATCH v5 4/9] iomap: Add iomap_get_folio helper

Darrick J. Wong
2023-01-04T17:38:19Z

On Sat, Dec 31, 2022 at 04:09:14PM +0100, Andreas Gruenbacher wrote:
> Add an iomap_get_folio() helper that gets a folio reference based on
> an iomap iterator and an offset into the address space. Use it in
> iomap_write_begin().
>
> Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

Pretty straightforward,
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> ---
> fs/iomap/buffered-io.c | 39 ++++++++++++++++++++++++++++++---------
> include/linux/iomap.h | 1 +
> 2 files changed, 31 insertions(+), 9 deletions(-)
>
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index 2a9bab4f3c79..b84838d2b5d8 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -457,6 +457,33 @@ bool iomap_is_partially_uptodate(struct folio *folio, size_t from, size_t count)
> }
> EXPORT_SYMBOL_GPL(iomap_is_partially_uptodate);
>
> +/**
> + * iomap_get_folio - get a folio reference for writing
> + * @iter: iteration structure
> + * @pos: start offset of write
> + *
> + * Returns a locked reference to the folio at @pos, or an error pointer if the
> + * folio could not be obtained.
> + */
> +struct folio *iomap_get_folio(struct iomap_iter *iter, loff_t pos)
> +{
> + unsigned fgp = FGP_LOCK | FGP_WRITE | FGP_CREAT | FGP_STABLE | FGP_NOFS;
> + struct folio *folio;
> +
> + if (iter->flags & IOMAP_NOWAIT)
> + fgp |= FGP_NOWAIT;
> +
> + folio = __filemap_get_folio(iter->inode->i_mapping, pos >> PAGE_SHIFT,
> + fgp, mapping_gfp_mask(iter->inode->i_mapping));
> + if (folio)
> + return folio;
> +
> + if (iter->flags & IOMAP_NOWAIT)
> + return ERR_PTR(-EAGAIN);
> + return ERR_PTR(-ENOMEM);
> +}
> +EXPORT_SYMBOL_GPL(iomap_get_folio);
> +
> bool iomap_release_folio(struct folio *folio, gfp_t gfp_flags)
> {
> trace_iomap_release_folio(folio->mapping->host, folio_pos(folio),
> @@ -603,12 +630,8 @@ static int iomap_write_begin(struct iomap_iter *iter, loff_t pos,
> const struct iomap_page_ops *page_ops = iter->iomap.page_ops;
> const struct iomap *srcmap = iomap_iter_srcmap(iter);
> struct folio *folio;
> - unsigned fgp = FGP_LOCK | FGP_WRITE | FGP_CREAT | FGP_STABLE | FGP_NOFS;
> int status = 0;
>
> - if (iter->flags & IOMAP_NOWAIT)
> - fgp |= FGP_NOWAIT;
> -
> BUG_ON(pos + len > iter->iomap.offset + iter->iomap.length);
> if (srcmap != &iter->iomap)
> BUG_ON(pos + len > srcmap->offset + srcmap->length);
> @@ -625,12 +648,10 @@ static int iomap_write_begin(struct iomap_iter *iter, loff_t pos,
> return status;
> }
>
> - folio = __filemap_get_folio(iter->inode->i_mapping, pos >> PAGE_SHIFT,
> - fgp, mapping_gfp_mask(iter->inode->i_mapping));
> - if (!folio) {
> - status = (iter->flags & IOMAP_NOWAIT) ? -EAGAIN : -ENOMEM;
> + folio = iomap_get_folio(iter, pos);
> + if (IS_ERR(folio)) {
> iomap_put_folio(iter, pos, 0, NULL);
> - return status;
> + return PTR_ERR(folio);
> }
>
> /*
> diff --git a/include/linux/iomap.h b/include/linux/iomap.h
> index 10ec36f373f4..e5732cc5716b 100644
> --- a/include/linux/iomap.h
> +++ b/include/linux/iomap.h
> @@ -261,6 +261,7 @@ int iomap_file_buffered_write_punch_delalloc(struct inode *inode,
> int iomap_read_folio(struct folio *folio, const struct iomap_ops *ops);
> void iomap_readahead(struct readahead_control *, const struct iomap_ops *ops);
> bool iomap_is_partially_uptodate(struct folio *, size_t from, size_t count);
> +struct folio *iomap_get_folio(struct iomap_iter *iter, loff_t pos);
> bool iomap_release_folio(struct folio *folio, gfp_t gfp_flags);
> void iomap_invalidate_folio(struct folio *folio, size_t offset, size_t len);
> int iomap_file_unshare(struct inode *inode, loff_t pos, loff_t len,
> --
> 2.38.1
>