[PATCH v2 10/16] iomap: make iomap_read_folio_ctx->folio_owned internal

[Joanne Koong <joannelkoong@gmail.com>]

struct iomap_read_folio_ctx will be made a public interface when
read/readahead takes in caller-provided callbacks.

To make the interface simpler for end users, keep track of the folio
ownership state internally instead of exposing it in struct
iomap_read_folio_ctx.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
---
 fs/iomap/buffered-io.c | 39 +++++++++++++++++++++++----------------
 1 file changed, 23 insertions(+), 16 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 50de09426c96..d38459740180 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -365,12 +365,6 @@ static void iomap_read_end_io(struct bio *bio)
 
 struct iomap_read_folio_ctx {
 	struct folio		*cur_folio;
-	/*
-	 * Is the folio owned by this readpage context, or by some
-	 * external IO helper?  Either way, the owner of the folio is
-	 * responsible for unlocking it when the read completes.
-	 */
-	bool			folio_owned;
 	void			*private;
 	struct readahead_control *rac;
 };
@@ -399,7 +393,6 @@ static void iomap_read_folio_range_bio_async(const struct iomap_iter *iter,
 	sector_t sector;
 	struct bio *bio = ctx->private;
 
-	ctx->folio_owned = true;
 	iomap_start_folio_read(folio, plen);
 
 	sector = iomap_sector(iomap, pos);
@@ -432,7 +425,7 @@ static void iomap_read_folio_range_bio_async(const struct iomap_iter *iter,
 }
 
 static int iomap_read_folio_iter(struct iomap_iter *iter,
-		struct iomap_read_folio_ctx *ctx)
+		struct iomap_read_folio_ctx *ctx, bool *cur_folio_owned)
 {
 	const struct iomap *iomap = &iter->iomap;
 	loff_t pos = iter->pos;
@@ -465,6 +458,7 @@ static int iomap_read_folio_iter(struct iomap_iter *iter,
 			folio_zero_range(folio, poff, plen);
 			iomap_set_range_uptodate(folio, poff, plen);
 		} else {
+			*cur_folio_owned = true;
 			iomap_read_folio_range_bio_async(iter, ctx, pos, plen);
 		}
 
@@ -487,16 +481,22 @@ int iomap_read_folio(struct folio *folio, const struct iomap_ops *ops)
 	struct iomap_read_folio_ctx ctx = {
 		.cur_folio	= folio,
 	};
+	/*
+	 * If an external IO helper takes ownership of the folio,
+	 * it is responsible for unlocking it when the read completes.
+	 */
+	bool cur_folio_owned = false;
 	int ret;
 
 	trace_iomap_readpage(iter.inode, 1);
 
 	while ((ret = iomap_iter(&iter, ops)) > 0)
-		iter.status = iomap_read_folio_iter(&iter, &ctx);
+		iter.status = iomap_read_folio_iter(&iter, &ctx,
+				&cur_folio_owned);
 
 	iomap_submit_read_bio(&ctx);
 
-	if (!ctx.folio_owned)
+	if (!cur_folio_owned)
 		folio_unlock(folio);
 
 	return ret;
@@ -504,12 +504,13 @@ int iomap_read_folio(struct folio *folio, const struct iomap_ops *ops)
 EXPORT_SYMBOL_GPL(iomap_read_folio);
 
 static int iomap_readahead_iter(struct iomap_iter *iter,
-		struct iomap_read_folio_ctx *ctx)
+		struct iomap_read_folio_ctx *ctx,
+		bool *cur_folio_owned)
 {
 	int ret;
 
 	while (iomap_length(iter)) {
-		if (ctx->cur_folio && !ctx->folio_owned)
+		if (ctx->cur_folio && !*cur_folio_owned)
 			folio_unlock(ctx->cur_folio);
 		ctx->cur_folio = readahead_folio(ctx->rac);
 		/*
@@ -518,8 +519,8 @@ static int iomap_readahead_iter(struct iomap_iter *iter,
 		 */
 		if (WARN_ON_ONCE(!ctx->cur_folio))
 			return -EINVAL;
-		ctx->folio_owned = false;
-		ret = iomap_read_folio_iter(iter, ctx);
+		*cur_folio_owned = false;
+		ret = iomap_read_folio_iter(iter, ctx, cur_folio_owned);
 		if (ret)
 			return ret;
 	}
@@ -552,15 +553,21 @@ void iomap_readahead(struct readahead_control *rac, const struct iomap_ops *ops)
 	struct iomap_read_folio_ctx ctx = {
 		.rac	= rac,
 	};
+	/*
+	 * If an external IO helper takes ownership of the folio,
+	 * it is responsible for unlocking it when the read completes.
+	 */
+	bool cur_folio_owned = false;
 
 	trace_iomap_readahead(rac->mapping->host, readahead_count(rac));
 
 	while (iomap_iter(&iter, ops) > 0)
-		iter.status = iomap_readahead_iter(&iter, &ctx);
+		iter.status = iomap_readahead_iter(&iter, &ctx,
+					&cur_folio_owned);
 
 	iomap_submit_read_bio(&ctx);
 
-	if (ctx.cur_folio && !ctx.folio_owned)
+	if (ctx.cur_folio && !cur_folio_owned)
 		folio_unlock(ctx.cur_folio);
 }
 EXPORT_SYMBOL_GPL(iomap_readahead);
-- 
2.47.3