[PATCH 09/10] iomap: remove unnecessary advance from iomap_iter()

Brian Foster
2025-02-12T13:55:02Z

At this point, all iomap operations have been updated to advance the
iomap_iter directly before returning to iomap_iter(). Therefore, the
complexity of handling both the old and new semantics is no longer
required and can be removed from iomap_iter().

Update iomap_iter() to expect success or failure status in
iter.processed. As a precaution and developer hint to prevent
inadvertent use of old semantics, warn on a positive return code and
fail the operation. Remove the unnecessary advance and simplify the
termination logic.

Signed-off-by: Brian Foster <bfoster@redhat.com>
---
fs/iomap/iter.c | 38 ++++++++++++++------------------------
1 file changed, 14 insertions(+), 24 deletions(-)

diff --git a/fs/iomap/iter.c b/fs/iomap/iter.c
index 0ebcabc7df52..1e2e5c834582 100644
--- a/fs/iomap/iter.c
+++ b/fs/iomap/iter.c
@@ -60,9 +60,8 @@ static inline void iomap_iter_done(struct iomap_iter *iter)
int iomap_iter(struct iomap_iter *iter, const struct iomap_ops *ops)
{
bool stale = iter->iomap.flags & IOMAP_F_STALE;
- ssize_t advanced = iter->processed > 0 ? iter->processed : 0;
- u64 olen = iter->len;
- s64 processed;
+ ssize_t advanced;
+ u64 olen;
int ret;

trace_iomap_iter(iter, ops, _RET_IP_);
@@ -71,14 +70,11 @@ int iomap_iter(struct iomap_iter *iter, const struct iomap_ops *ops)
goto begin;

/*
- * If iter.processed is zero, the op may still have advanced the iter
- * itself. Calculate the advanced and original length bytes based on how
- * far pos has advanced for ->iomap_end().
+ * Calculate how far the iter was advanced and the original length bytes
+ * for ->iomap_end().
*/
- if (!advanced) {
- advanced = iter->pos - iter->iter_start_pos;
- olen += advanced;
- }
+ advanced = iter->pos - iter->iter_start_pos;
+ olen = iter->len + advanced;

if (ops->iomap_end) {
ret = ops->iomap_end(iter->inode, iter->iter_start_pos,
@@ -89,26 +85,20 @@ int iomap_iter(struct iomap_iter *iter, const struct iomap_ops *ops)
return ret;
}

- processed = iter->processed;
- if (processed < 0) {
- iomap_iter_reset_iomap(iter);
- return processed;
- }
+ /* detect old return semantics where this would advance */
+ if (WARN_ON_ONCE(iter->processed > 0))
+ iter->processed = -EIO;

/*
- * Advance the iter and clear state from the previous iteration. This
- * passes iter->processed because that reflects the bytes processed but
- * not yet advanced by the iter handler.
- *
* Use iter->len to determine whether to continue onto the next mapping.
- * Explicitly terminate in the case where the current iter has not
+ * Explicitly terminate on error status or if the current iter has not
* 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);
- if (!ret && iter->len > 0)
- ret = 1;
- if (ret > 0 && !advanced && !stale)
+ ret = (iter->len > 0) ? 1 : 0;
+ if (iter->processed < 0)
+ ret = iter->processed;
+ else if (!advanced && !stale)
ret = 0;
iomap_iter_reset_iomap(iter);
if (ret <= 0)
--
2.48.1