md: simplify sync_page_io

Use an on-stack bio and biovec for the single page synchronous I/O.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Song Liu <song@kernel.org>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Acked-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/md/md.c

@@ -1021,29 +1021,29 @@ int md_super_wait(struct mddev *mddev)
 int sync_page_io(struct md_rdev *rdev, sector_t sector, int size,
 		 struct page *page, int op, int op_flags, bool metadata_op)
 {
-	struct bio *bio = md_bio_alloc_sync(rdev->mddev);
-	int ret;
+	struct bio bio;
+	struct bio_vec bvec;
+
+	bio_init(&bio, &bvec, 1);
 
 	if (metadata_op && rdev->meta_bdev)
-		bio_set_dev(bio, rdev->meta_bdev);
+		bio_set_dev(&bio, rdev->meta_bdev);
 	else
-		bio_set_dev(bio, rdev->bdev);
-	bio_set_op_attrs(bio, op, op_flags);
+		bio_set_dev(&bio, rdev->bdev);
+	bio.bi_opf = op | op_flags;
 	if (metadata_op)
-		bio->bi_iter.bi_sector = sector + rdev->sb_start;
+		bio.bi_iter.bi_sector = sector + rdev->sb_start;
 	else if (rdev->mddev->reshape_position != MaxSector &&
 		 (rdev->mddev->reshape_backwards ==
 		  (sector >= rdev->mddev->reshape_position)))
-		bio->bi_iter.bi_sector = sector + rdev->new_data_offset;
+		bio.bi_iter.bi_sector = sector + rdev->new_data_offset;
 	else
-		bio->bi_iter.bi_sector = sector + rdev->data_offset;
-	bio_add_page(bio, page, size, 0);
+		bio.bi_iter.bi_sector = sector + rdev->data_offset;
+	bio_add_page(&bio, page, size, 0);
 
-	submit_bio_wait(bio);
+	submit_bio_wait(&bio);
 
-	ret = !bio->bi_status;
-	bio_put(bio);
-	return ret;
+	return !bio.bi_status;
 }
 EXPORT_SYMBOL_GPL(sync_page_io);