[PATCH v5 04/14] iomap: iterate over folio mapping in iomap_readpage_iter()

Joanne Koong
2025-09-26T00:29:32Z

Iterate over all non-uptodate ranges of a folio mapping in a single call
to iomap_readpage_iter() instead of leaving the partial iteration to the
caller.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
---
fs/iomap/buffered-io.c | 53 ++++++++++++++++++++----------------------
1 file changed, 25 insertions(+), 28 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index b06b532033ad..dbe5783ee68c 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -430,6 +430,7 @@ static int iomap_readpage_iter(struct iomap_iter *iter,
loff_t length = iomap_length(iter);
struct folio *folio = ctx->cur_folio;
size_t poff, plen;
+ loff_t count;
int ret;

if (iomap->type == IOMAP_INLINE) {
@@ -439,41 +440,35 @@ static int iomap_readpage_iter(struct iomap_iter *iter,
return iomap_iter_advance(iter, length);
}

- /* zero post-eof blocks as the page may be mapped */
ifs_alloc(iter->inode, folio, iter->flags);
- iomap_adjust_read_range(iter->inode, folio, &pos, length, &poff, &plen);
- if (plen == 0)
- goto done;

- if (iomap_block_needs_zeroing(iter, pos)) {
- folio_zero_range(folio, poff, plen);
- iomap_set_range_uptodate(folio, poff, plen);
- } else {
- iomap_bio_read_folio_range(iter, ctx, pos, plen);
- }
+ length = min_t(loff_t, length,
+ folio_size(folio) - offset_in_folio(folio, pos));
+ while (length) {
+ iomap_adjust_read_range(iter->inode, folio, &pos, length, &poff,
+ &plen);

-done:
- /*
- * Move the caller beyond our range so that it keeps making progress.
- * For that, we have to include any leading non-uptodate ranges, but
- * we can skip trailing ones as they will be handled in the next
- * iteration.
- */
- length = pos - iter->pos + plen;
- return iomap_iter_advance(iter, length);
-}
+ count = pos - iter->pos + plen;
+ if (WARN_ON_ONCE(count > length))
+ return -EIO;

-static int iomap_read_folio_iter(struct iomap_iter *iter,
- struct iomap_readpage_ctx *ctx)
-{
- int ret;
+ if (plen == 0)
+ return iomap_iter_advance(iter, count);

- while (iomap_length(iter)) {
- ret = iomap_readpage_iter(iter, ctx);
+ /* zero post-eof blocks as the page may be mapped */
+ if (iomap_block_needs_zeroing(iter, pos)) {
+ folio_zero_range(folio, poff, plen);
+ iomap_set_range_uptodate(folio, poff, plen);
+ } else {
+ iomap_bio_read_folio_range(iter, ctx, pos, plen);
+ }
+
+ ret = iomap_iter_advance(iter, count);
if (ret)
return ret;
+ length -= count;
+ pos = iter->pos;
}
-
return 0;
}

@@ -492,7 +487,7 @@ int iomap_read_folio(struct folio *folio, const struct iomap_ops *ops)
trace_iomap_readpage(iter.inode, 1);

while ((ret = iomap_iter(&iter, ops)) > 0)
- iter.status = iomap_read_folio_iter(&iter, &ctx);
+ iter.status = iomap_readpage_iter(&iter, &ctx);

iomap_bio_submit_read(&ctx);

@@ -522,6 +517,8 @@ static int iomap_readahead_iter(struct iomap_iter *iter,
}
if (!ctx->cur_folio) {
ctx->cur_folio = readahead_folio(ctx->rac);
+ if (WARN_ON_ONCE(!ctx->cur_folio))
+ return -EINVAL;
ctx->cur_folio_in_bio = false;
}
ret = iomap_readpage_iter(iter, ctx);
--
2.47.3