[PATCH 01/10] iomap: advance the iter directly on buffered read

[Brian Foster <bfoster@xxxxxxxxxx>]

iomap buffered read advances the iter via iter.processed. To
continue separating iter advance from return status, update
iomap_readpage_iter() to advance the iter instead of returning the
number of bytes processed. In turn, drop the offset parameter and
sample the updated iter->pos at the start of the function. Update
the callers to loop based on remaining length in the current
iteration instead of number of bytes processed.

Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
---
 fs/iomap/buffered-io.c | 44 +++++++++++++++++++-----------------------
 1 file changed, 20 insertions(+), 24 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index ec227b45f3aa..44a366736289 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -366,12 +366,12 @@ static inline bool iomap_block_needs_zeroing(const struct iomap_iter *iter,
 		pos >= i_size_read(iter->inode);
 }
 
-static loff_t iomap_readpage_iter(const struct iomap_iter *iter,
-		struct iomap_readpage_ctx *ctx, loff_t offset)
+static loff_t iomap_readpage_iter(struct iomap_iter *iter,
+		struct iomap_readpage_ctx *ctx)
 {
 	const struct iomap *iomap = &iter->iomap;
-	loff_t pos = iter->pos + offset;
-	loff_t length = iomap_length(iter) - offset;
+	loff_t pos = iter->pos;
+	loff_t length = iomap_length(iter);
 	struct folio *folio = ctx->cur_folio;
 	struct iomap_folio_state *ifs;
 	loff_t orig_pos = pos;
@@ -438,25 +438,22 @@ static loff_t iomap_readpage_iter(const struct iomap_iter *iter,
 	 * we can skip trailing ones as they will be handled in the next
 	 * iteration.
 	 */
-	return pos - orig_pos + plen;
+	length = pos - orig_pos + plen;
+	return iomap_iter_advance(iter, &length);
 }
 
-static loff_t iomap_read_folio_iter(const struct iomap_iter *iter,
+static loff_t iomap_read_folio_iter(struct iomap_iter *iter,
 		struct iomap_readpage_ctx *ctx)
 {
-	struct folio *folio = ctx->cur_folio;
-	size_t offset = offset_in_folio(folio, iter->pos);
-	loff_t length = min_t(loff_t, folio_size(folio) - offset,
-			      iomap_length(iter));
-	loff_t done, ret;
-
-	for (done = 0; done < length; done += ret) {
-		ret = iomap_readpage_iter(iter, ctx, done);
-		if (ret <= 0)
+	loff_t ret;
+
+	while (iomap_length(iter)) {
+		ret = iomap_readpage_iter(iter, ctx);
+		if (ret)
 			return ret;
 	}
 
-	return done;
+	return 0;
 }
 
 int iomap_read_folio(struct folio *folio, const struct iomap_ops *ops)
@@ -493,15 +490,14 @@ int iomap_read_folio(struct folio *folio, const struct iomap_ops *ops)
 }
 EXPORT_SYMBOL_GPL(iomap_read_folio);
 
-static loff_t iomap_readahead_iter(const struct iomap_iter *iter,
+static loff_t iomap_readahead_iter(struct iomap_iter *iter,
 		struct iomap_readpage_ctx *ctx)
 {
-	loff_t length = iomap_length(iter);
-	loff_t done, ret;
+	loff_t ret;
 
-	for (done = 0; done < length; done += ret) {
+	while (iomap_length(iter) > 0) {
 		if (ctx->cur_folio &&
-		    offset_in_folio(ctx->cur_folio, iter->pos + done) == 0) {
+		    offset_in_folio(ctx->cur_folio, iter->pos) == 0) {
 			if (!ctx->cur_folio_in_bio)
 				folio_unlock(ctx->cur_folio);
 			ctx->cur_folio = NULL;
@@ -510,12 +506,12 @@ static loff_t iomap_readahead_iter(const struct iomap_iter *iter,
 			ctx->cur_folio = readahead_folio(ctx->rac);
 			ctx->cur_folio_in_bio = false;
 		}
-		ret = iomap_readpage_iter(iter, ctx, done);
-		if (ret <= 0)
+		ret = iomap_readpage_iter(iter, ctx);
+		if (ret)
 			return ret;
 	}
 
-	return done;
+	return 0;
 }
 
 /**
-- 
2.48.1