Re: [PATCH v6 06/10] iomap: export iomap_iter_advance() and return remaining length

Darrick J. Wong
2025-02-07T17:17:55Z

On Fri, Feb 07, 2025 at 09:32:49AM -0500, Brian Foster wrote:
> As a final step for generic iter advance, export the helper and
> update it to return the remaining length of the current iteration
> after the advance. This will usually be 0 in the iomap_iter() case,
> but will be useful for the various operations that iterate on their
> own and will be updated to advance as they progress.
>
> Signed-off-by: Brian Foster <bfoster@redhat.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Looks good to me now,
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> ---
> fs/iomap/iter.c | 22 ++++++++--------------
> include/linux/iomap.h | 1 +
> 2 files changed, 9 insertions(+), 14 deletions(-)
>
> diff --git a/fs/iomap/iter.c b/fs/iomap/iter.c
> index 8e0746ad80bd..544cd7a5a16b 100644
> --- a/fs/iomap/iter.c
> +++ b/fs/iomap/iter.c
> @@ -15,22 +15,16 @@ static inline void iomap_iter_reset_iomap(struct iomap_iter *iter)
> }
>
> /*
> - * Advance to the next range we need to map.
> - *
> - * If the iomap is marked IOMAP_F_STALE, it means the existing map was not fully
> - * processed - it was aborted because the extent the iomap spanned may have been
> - * changed during the operation. In this case, the iteration behaviour is to
> - * remap the unprocessed range of the iter, and that means we may need to remap
> - * even when we've made no progress (i.e. count = 0). Hence the "finished
> - * iterating" case needs to distinguish between (count = 0) meaning we are done
> - * and (count = 0 && stale) meaning we need to remap the entire remaining range.
> + * Advance the current iterator position and output the length remaining for the
> + * current mapping.
> */
> -static inline int iomap_iter_advance(struct iomap_iter *iter, s64 count)
> +int iomap_iter_advance(struct iomap_iter *iter, u64 *count)
> {
> - if (WARN_ON_ONCE(count > iomap_length(iter)))
> + if (WARN_ON_ONCE(*count > iomap_length(iter)))
> return -EIO;
> - iter->pos += count;
> - iter->len -= count;
> + iter->pos += *count;
> + iter->len -= *count;
> + *count = iomap_length(iter);
> return 0;
> }
>
> @@ -93,7 +87,7 @@ int iomap_iter(struct iomap_iter *iter, const struct iomap_ops *ops)
> * advanced at all (i.e. no work was done for some reason) unless the
> * mapping has been marked stale and needs to be reprocessed.
> */
> - ret = iomap_iter_advance(iter, processed);
> + ret = iomap_iter_advance(iter, &processed);
> if (!ret && iter->len > 0)
> ret = 1;
> if (ret > 0 && !iter->processed && !stale)
> diff --git a/include/linux/iomap.h b/include/linux/iomap.h
> index f5ca71ac2fa2..f304c602e5fe 100644
> --- a/include/linux/iomap.h
> +++ b/include/linux/iomap.h
> @@ -229,6 +229,7 @@ struct iomap_iter {
> };
>
> int iomap_iter(struct iomap_iter *iter, const struct iomap_ops *ops);
> +int iomap_iter_advance(struct iomap_iter *iter, u64 *count);
>
> /**
> * iomap_length_trim - trimmed length of the current iomap iteration
> --
> 2.48.1
>
>