iomap: support ioends for buffered reads

Support using the ioend structure to defer I/O completion for
buffered reads by calling into the buffered read I/O completion
handler from iomap_finish_ioend.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://patch.msgid.link/20260223132021.292832-15-hch@lst.de
Tested-by: Anuj Gupta <anuj20.g@samsung.com>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: Christoph Hellwig

fs/iomap/bio.c

@@ -8,14 +8,27 @@
 #include "internal.h"
 #include "trace.h"
 
-static void iomap_read_end_io(struct bio *bio)
+static u32 __iomap_read_end_io(struct bio *bio, int error)
 {
-	int error = blk_status_to_errno(bio->bi_status);
 	struct folio_iter fi;
+	u32 folio_count = 0;
 
-	bio_for_each_folio_all(fi, bio)
+	bio_for_each_folio_all(fi, bio) {
 		iomap_finish_folio_read(fi.folio, fi.offset, fi.length, error);
+		folio_count++;
+	}
 	bio_put(bio);
+	return folio_count;
+}
+
+static void iomap_read_end_io(struct bio *bio)
+{
+	__iomap_read_end_io(bio, blk_status_to_errno(bio->bi_status));
+}
+
+u32 iomap_finish_ioend_buffered_read(struct iomap_ioend *ioend)
+{
+	return __iomap_read_end_io(&ioend->io_bio, ioend->io_error);
 }
 
 static void iomap_bio_submit_read(const struct iomap_iter *iter,

fs/iomap/internal.h

@@ -4,6 +4,7 @@
 
 #define IOEND_BATCH_SIZE	4096
 
+u32 iomap_finish_ioend_buffered_read(struct iomap_ioend *ioend);
 u32 iomap_finish_ioend_direct(struct iomap_ioend *ioend);
 
 #ifdef CONFIG_BLOCK

fs/iomap/ioend.c

@@ -37,7 +37,7 @@ EXPORT_SYMBOL_GPL(iomap_init_ioend);
  * state, release holds on bios, and finally free up memory.  Do not use the
  * ioend after this.
  */
-static u32 iomap_finish_ioend_buffered(struct iomap_ioend *ioend)
+static u32 iomap_finish_ioend_buffered_write(struct iomap_ioend *ioend)
 {
 	struct inode *inode = ioend->io_inode;
 	struct bio *bio = &ioend->io_bio;
@@ -87,7 +87,7 @@ iomap_fail_ioends(
 	while ((ioend = list_first_entry_or_null(&tmp, struct iomap_ioend,
 			io_list))) {
 		list_del_init(&ioend->io_list);
-		iomap_finish_ioend_buffered(ioend);
+		iomap_finish_ioend_buffered_write(ioend);
 		cond_resched();
 	}
 }
@@ -120,7 +120,7 @@ static void ioend_writeback_end_bio(struct bio *bio)
 		return;
 	}
 
-	iomap_finish_ioend_buffered(ioend);
+	iomap_finish_ioend_buffered_write(ioend);
 }
 
 /*
@@ -313,7 +313,9 @@ static u32 iomap_finish_ioend(struct iomap_ioend *ioend, int error)
 		return 0;
 	if (ioend->io_flags & IOMAP_IOEND_DIRECT)
 		return iomap_finish_ioend_direct(ioend);
-	return iomap_finish_ioend_buffered(ioend);
+	if (bio_op(&ioend->io_bio) == REQ_OP_READ)
+		return iomap_finish_ioend_buffered_read(ioend);
+	return iomap_finish_ioend_buffered_write(ioend);
 }
 
 /*