[PATCH RFC md-6.16 v3 02/19] md: support discard for bitmap ops

[Yu Kuai <yukuai1@xxxxxxxxxxxxxxx>]

From: Yu Kuai <yukuai3@xxxxxxxxxx>

If {start, end}_discard is implemented from bitmap_operations, then they
will be used to handle discard IO. Currently md-bitmap handle discard
the same as normal write, prepare to support discard for new md bitmap.

Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
 drivers/md/md.c | 19 +++++++++++++++----
 drivers/md/md.h |  1 +
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 32b997dfe6f4..c72c13ed4253 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -8849,14 +8849,24 @@ static void md_bitmap_start(struct mddev *mddev,
 		mddev->pers->bitmap_sector(mddev, &md_io_clone->offset,
 					   &md_io_clone->sectors);
 
-	mddev->bitmap_ops->startwrite(mddev, md_io_clone->offset,
-				      md_io_clone->sectors);
+	if (unlikely(md_io_clone->rw == STAT_DISCARD) &&
+	    mddev->bitmap_ops->start_discard)
+		mddev->bitmap_ops->start_discard(mddev, md_io_clone->offset,
+						 md_io_clone->sectors);
+	else
+		mddev->bitmap_ops->startwrite(mddev, md_io_clone->offset,
+					      md_io_clone->sectors);
 }
 
 static void md_bitmap_end(struct mddev *mddev, struct md_io_clone *md_io_clone)
 {
-	mddev->bitmap_ops->endwrite(mddev, md_io_clone->offset,
-				    md_io_clone->sectors);
+	if (unlikely(md_io_clone->rw == STAT_DISCARD) &&
+	    mddev->bitmap_ops->end_discard)
+		mddev->bitmap_ops->end_discard(mddev, md_io_clone->offset,
+					       md_io_clone->sectors);
+	else
+		mddev->bitmap_ops->endwrite(mddev, md_io_clone->offset,
+					    md_io_clone->sectors);
 }
 
 static void md_end_clone_io(struct bio *bio)
@@ -8895,6 +8905,7 @@ static void md_clone_bio(struct mddev *mddev, struct bio **bio)
 	if (bio_data_dir(*bio) == WRITE && md_bitmap_enabled(mddev)) {
 		md_io_clone->offset = (*bio)->bi_iter.bi_sector;
 		md_io_clone->sectors = bio_sectors(*bio);
+		md_io_clone->rw = op_stat_group(bio_op(*bio));
 		md_bitmap_start(mddev, md_io_clone);
 	}
 
diff --git a/drivers/md/md.h b/drivers/md/md.h
index 6eb5dfdf2f55..c474bf74c345 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -850,6 +850,7 @@ struct md_io_clone {
 	unsigned long	start_time;
 	sector_t	offset;
 	unsigned long	sectors;
+	enum stat_group	rw;
 	struct bio	bio_clone;
 };
 
-- 
2.39.2