block: replace bi_bdev with a gendisk pointer and partitions index

This way we don't need a block_device structure to submit I/O.  The
block_device has different life time rules from the gendisk and
request_queue and is usually only available when the block device node
is open.  Other callers need to explicitly create one (e.g. the lightnvm
passthrough code, or the new nvme multipathing code).

For the actual I/O path all that we need is the gendisk, which exists
once per block device.  But given that the block layer also does
partition remapping we additionally need a partition index, which is
used for said remapping in generic_make_request.

Note that all the block drivers generally want request_queue or
sometimes the gendisk, so this removes a layer of indirection all
over the stack.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index 6f1e4c9..b0b71e8 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -1738,7 +1738,7 @@ static void scrub_recheck_block(struct btrfs_fs_info *fs_info,
 
 		WARN_ON(!page->page);
 		bio = btrfs_io_bio_alloc(1);
-		bio->bi_bdev = page->dev->bdev;
+		bio_set_dev(bio, page->dev->bdev);
 
 		bio_add_page(bio, page->page, PAGE_SIZE, 0);
 		if (!retry_failed_mirror && scrub_is_page_on_raid56(page)) {
@@ -1826,7 +1826,7 @@ static int scrub_repair_page_from_good_copy(struct scrub_block *sblock_bad,
 		}
 
 		bio = btrfs_io_bio_alloc(1);
-		bio->bi_bdev = page_bad->dev->bdev;
+		bio_set_dev(bio, page_bad->dev->bdev);
 		bio->bi_iter.bi_sector = page_bad->physical >> 9;
 		bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
 
@@ -1921,7 +1921,7 @@ static int scrub_add_page_to_wr_bio(struct scrub_ctx *sctx,
 
 		bio->bi_private = sbio;
 		bio->bi_end_io = scrub_wr_bio_end_io;
-		bio->bi_bdev = sbio->dev->bdev;
+		bio_set_dev(bio, sbio->dev->bdev);
 		bio->bi_iter.bi_sector = sbio->physical >> 9;
 		bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
 		sbio->status = 0;
@@ -1964,7 +1964,7 @@ static void scrub_wr_submit(struct scrub_ctx *sctx)
 
 	sbio = sctx->wr_curr_bio;
 	sctx->wr_curr_bio = NULL;
-	WARN_ON(!sbio->bio->bi_bdev);
+	WARN_ON(!sbio->bio->bi_disk);
 	scrub_pending_bio_inc(sctx);
 	/* process all writes in a single worker thread. Then the block layer
 	 * orders the requests before sending them to the driver which
@@ -2321,7 +2321,7 @@ static int scrub_add_page_to_rd_bio(struct scrub_ctx *sctx,
 
 		bio->bi_private = sbio;
 		bio->bi_end_io = scrub_bio_end_io;
-		bio->bi_bdev = sbio->dev->bdev;
+		bio_set_dev(bio, sbio->dev->bdev);
 		bio->bi_iter.bi_sector = sbio->physical >> 9;
 		bio_set_op_attrs(bio, REQ_OP_READ, 0);
 		sbio->status = 0;
@@ -4627,7 +4627,7 @@ static int write_page_nocow(struct scrub_ctx *sctx,
 	bio = btrfs_io_bio_alloc(1);
 	bio->bi_iter.bi_size = 0;
 	bio->bi_iter.bi_sector = physical_for_dev_replace >> 9;
-	bio->bi_bdev = dev->bdev;
+	bio_set_dev(bio, dev->bdev);
 	bio->bi_opf = REQ_OP_WRITE | REQ_SYNC;
 	ret = bio_add_page(bio, page, PAGE_SIZE, 0);
 	if (ret != PAGE_SIZE) {