[PATCH v1 04/16] iomap: use iomap_iter->private for stashing read/readahead bio

[Joanne Koong <joannelkoong@xxxxxxxxx>]

Use the iomap_iter->private field for stashing any read/readahead bios
instead of defining the bio as part of the iomap_readpage_ctx struct.
This makes the read/readahead interface more generic. Some filesystems
that will be using iomap for read/readahead may not have CONFIG_BLOCK
set.

Signed-off-by: Joanne Koong <joannelkoong@xxxxxxxxx>
---
 fs/iomap/buffered-io.c | 49 +++++++++++++++++++++---------------------
 1 file changed, 25 insertions(+), 24 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index f2bfb3e17bb0..9db233a4a82c 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -353,11 +353,10 @@ static void iomap_read_end_io(struct bio *bio)
 struct iomap_readpage_ctx {
 	struct folio		*cur_folio;
 	bool			folio_unlocked;
-	struct bio		*bio;
 	struct readahead_control *rac;
 };
 
-static void iomap_read_folio_range_async(const struct iomap_iter *iter,
+static void iomap_read_folio_range_async(struct iomap_iter *iter,
 		struct iomap_readpage_ctx *ctx, loff_t pos, size_t plen)
 {
 	struct folio *folio = ctx->cur_folio;
@@ -365,6 +364,7 @@ static void iomap_read_folio_range_async(const struct iomap_iter *iter,
 	struct iomap_folio_state *ifs = folio->private;
 	size_t poff = offset_in_folio(folio, pos);
 	loff_t length = iomap_length(iter);
+	struct bio *bio = iter->private;
 	sector_t sector;
 
 	ctx->folio_unlocked = true;
@@ -375,34 +375,32 @@ static void iomap_read_folio_range_async(const struct iomap_iter *iter,
 	}
 
 	sector = iomap_sector(iomap, pos);
-	if (!ctx->bio ||
-	    bio_end_sector(ctx->bio) != sector ||
-	    !bio_add_folio(ctx->bio, folio, plen, poff)) {
+	if (!bio || bio_end_sector(bio) != sector ||
+	    !bio_add_folio(bio, folio, plen, poff)) {
 		gfp_t gfp = mapping_gfp_constraint(folio->mapping, GFP_KERNEL);
 		gfp_t orig_gfp = gfp;
 		unsigned int nr_vecs = DIV_ROUND_UP(length, PAGE_SIZE);
 
-		if (ctx->bio)
-			submit_bio(ctx->bio);
+		if (bio)
+			submit_bio(bio);
 
 		if (ctx->rac) /* same as readahead_gfp_mask */
 			gfp |= __GFP_NORETRY | __GFP_NOWARN;
-		ctx->bio = bio_alloc(iomap->bdev, bio_max_segs(nr_vecs),
-				     REQ_OP_READ, gfp);
+		bio = bio_alloc(iomap->bdev, bio_max_segs(nr_vecs),
+				REQ_OP_READ, gfp);
 		/*
 		 * If the bio_alloc fails, try it again for a single page to
 		 * avoid having to deal with partial page reads.  This emulates
 		 * what do_mpage_read_folio does.
 		 */
-		if (!ctx->bio) {
-			ctx->bio = bio_alloc(iomap->bdev, 1, REQ_OP_READ,
-					     orig_gfp);
-		}
+		if (!bio)
+			bio = bio_alloc(iomap->bdev, 1, REQ_OP_READ, orig_gfp);
+		iter->private = bio;
 		if (ctx->rac)
-			ctx->bio->bi_opf |= REQ_RAHEAD;
-		ctx->bio->bi_iter.bi_sector = sector;
-		ctx->bio->bi_end_io = iomap_read_end_io;
-		bio_add_folio_nofail(ctx->bio, folio, plen, poff);
+			bio->bi_opf |= REQ_RAHEAD;
+		bio->bi_iter.bi_sector = sector;
+		bio->bi_end_io = iomap_read_end_io;
+		bio_add_folio_nofail(bio, folio, plen, poff);
 	}
 }
 
@@ -447,15 +445,18 @@ static int iomap_readpage_iter(struct iomap_iter *iter,
 	return iomap_iter_advance(iter, &length);
 }
 
-static void iomap_readfolio_submit(const struct iomap_readpage_ctx *ctx)
+static void iomap_readfolio_submit(const struct iomap_iter *iter)
 {
-	if (ctx->bio)
-		submit_bio(ctx->bio);
+	struct bio *bio = iter->private;
+
+	if (bio)
+		submit_bio(bio);
 }
 
-static void iomap_readfolio_complete(const struct iomap_readpage_ctx *ctx)
+static void iomap_readfolio_complete(const struct iomap_iter *iter,
+		const struct iomap_readpage_ctx *ctx)
 {
-	iomap_readfolio_submit(ctx);
+	iomap_readfolio_submit(iter);
 
 	if (ctx->cur_folio && !ctx->folio_unlocked)
 		folio_unlock(ctx->cur_folio);
@@ -492,7 +493,7 @@ int iomap_read_folio(struct folio *folio, const struct iomap_ops *ops)
 	while ((ret = iomap_iter(&iter, ops)) > 0)
 		iter.status = iomap_read_folio_iter(&iter, &ctx);
 
-	iomap_readfolio_complete(&ctx);
+	iomap_readfolio_complete(&iter, &ctx);
 
 	/*
 	 * Just like mpage_readahead and block_read_full_folio, we always
@@ -558,7 +559,7 @@ void iomap_readahead(struct readahead_control *rac, const struct iomap_ops *ops)
 	while (iomap_iter(&iter, ops) > 0)
 		iter.status = iomap_readahead_iter(&iter, &ctx);
 
-	iomap_readfolio_complete(&ctx);
+	iomap_readfolio_complete(&iter, &ctx);
 }
 EXPORT_SYMBOL_GPL(iomap_readahead);
 
-- 
2.47.3