[PATCH 4/7] iomap: support ioends for reads

[Christoph Hellwig <hch@xxxxxx>]

Support using the ioend structure to defer I/O completion for
reads in addition to writes.  This requires a check for the operation
to not merge reads and writes, and for buffere I/O a call into the
buffered read I/O completion handler from iomap_finish_ioend.  For
direct I/O the existing call into the direct I/O completion handler
handles reads just fine already.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 fs/iomap/buffered-io.c | 23 ++++++++++++++++++-----
 fs/iomap/internal.h    |  3 ++-
 fs/iomap/ioend.c       |  6 +++++-
 3 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index eaffa23eb8e4..06990e012884 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -306,14 +306,27 @@ static void iomap_finish_folio_read(struct folio *folio, size_t off,
 		folio_end_read(folio, uptodate);
 }
 
-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);
 }
 
 struct iomap_readpage_ctx {
@@ -1568,7 +1581,7 @@ static void iomap_finish_folio_write(struct inode *inode, struct folio *folio,
  * state, release holds on bios, and finally free up memory.  Do not use the
  * ioend after this.
  */
-u32 iomap_finish_ioend_buffered(struct iomap_ioend *ioend)
+u32 iomap_finish_ioend_buffered_write(struct iomap_ioend *ioend)
 {
 	struct inode *inode = ioend->io_inode;
 	struct bio *bio = &ioend->io_bio;
@@ -1600,7 +1613,7 @@ static void iomap_writepage_end_bio(struct bio *bio)
 	struct iomap_ioend *ioend = iomap_ioend_from_bio(bio);
 
 	ioend->io_error = blk_status_to_errno(bio->bi_status);
-	iomap_finish_ioend_buffered(ioend);
+	iomap_finish_ioend_buffered_write(ioend);
 }
 
 /*
diff --git a/fs/iomap/internal.h b/fs/iomap/internal.h
index f6992a3bf66a..c824e74a3526 100644
--- a/fs/iomap/internal.h
+++ b/fs/iomap/internal.h
@@ -4,7 +4,8 @@
 
 #define IOEND_BATCH_SIZE	4096
 
-u32 iomap_finish_ioend_buffered(struct iomap_ioend *ioend);
+u32 iomap_finish_ioend_buffered_read(struct iomap_ioend *ioend);
+u32 iomap_finish_ioend_buffered_write(struct iomap_ioend *ioend);
 u32 iomap_finish_ioend_direct(struct iomap_ioend *ioend);
 
 #endif /* _IOMAP_INTERNAL_H */
diff --git a/fs/iomap/ioend.c b/fs/iomap/ioend.c
index 18894ebba6db..2dd29403dc10 100644
--- a/fs/iomap/ioend.c
+++ b/fs/iomap/ioend.c
@@ -44,7 +44,9 @@ 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);
 }
 
 /*
@@ -83,6 +85,8 @@ EXPORT_SYMBOL_GPL(iomap_finish_ioends);
 static bool iomap_ioend_can_merge(struct iomap_ioend *ioend,
 		struct iomap_ioend *next)
 {
+	if (bio_op(&ioend->io_bio) != bio_op(&next->io_bio))
+		return false;
 	if (ioend->io_bio.bi_status != next->io_bio.bi_status)
 		return false;
 	if (next->io_flags & IOMAP_IOEND_BOUNDARY)
-- 
2.45.2