On Fri, Dec 16, 2022 at 04:06:25PM +0100, Andreas Gruenbacher wrote:
> Eliminate the ->iomap_valid() handler by switching to a ->page_prepare()
> handler and validating the mapping there.
>
> Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
> ---
> fs/iomap/buffered-io.c | 24 ++++--------------------
> fs/xfs/xfs_iomap.c | 38 +++++++++++++++++++++++++++-----------
> include/linux/iomap.h | 17 -----------------
> 3 files changed, 31 insertions(+), 48 deletions(-)
>
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index 6b7c1a10b8ec..b73ff317da21 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -623,7 +623,7 @@ 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;
> - int status = 0;
> + int status;
>
> BUG_ON(pos + len > iter->iomap.offset + iter->iomap.length);
> if (srcmap != &iter->iomap)
> @@ -642,27 +642,11 @@ static int iomap_write_begin(struct iomap_iter *iter, loff_t pos,
> if (IS_ERR_OR_NULL(folio)) {
> if (!folio)
> return (iter->flags & IOMAP_NOWAIT) ? -EAGAIN : -ENOMEM;
> + if (folio == ERR_PTR(-ESTALE)) {
> iter->iomap.flags |= IOMAP_F_STALE;
> + return 0;
> }
> + return PTR_ERR(folio);
> }
>
> if (pos + len > folio_pos(folio) + folio_size(folio))
> diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
> index 669c1bc5c3a7..2248ce7be2e3 100644
> --- a/fs/xfs/xfs_iomap.c
> +++ b/fs/xfs/xfs_iomap.c
> @@ -62,29 +62,45 @@ xfs_iomap_inode_sequence(
> return cookie | READ_ONCE(ip->i_df.if_seq);
> }
>
> -/*
> - * Check that the iomap passed to us is still valid for the given offset and
> - * length.
> - */
> -static bool
> -xfs_iomap_valid(
> - struct inode *inode,
> - const struct iomap *iomap)
> +static struct folio *
> +xfs_page_prepare(
> + struct iomap_iter *iter,
> + loff_t pos,
> + unsigned len)
> {
> + struct inode *inode = iter->inode;
> + struct iomap *iomap = &iter->iomap;
> struct xfs_inode *ip = XFS_I(inode);
> + struct folio *folio;
Please tab align this like the other variable declarations above.
> - /*
> - * Check that the cached iomap still maps correctly to the filesystem's
> - * internal extent map. FS internal extent maps can change while iomap
> - * is iterating a cached iomap, so this hook allows iomap to detect that
> - * the iomap needs to be refreshed during a long running write
> - * operation.
> - *
> - * The filesystem can store internal state (e.g. a sequence number) in
> - * iomap->validity_cookie when the iomap is first mapped to be able to
> - * detect changes between mapping time and whenever .iomap_valid() is
> - * called.
> - *
> - * This is called with the folio over the specified file position held
> - * locked by the iomap code.
> - */
We'll still need to capture this information somewhere. I'd suggest
to move it to the prepare/get method and reword it so that this is
mentioned as an additional use case / requirement.
