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>

1 files changed, 9 insertions, 8 deletions

diff --git a/mm/page_io.c b/mm/page_io.c
index b6c4ac38..9cf1bc7 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -31,7 +31,10 @@ static struct bio *get_swap_bio(gfp_t gfp_flags,
 
 	bio = bio_alloc(gfp_flags, 1);
 	if (bio) {
-		bio->bi_iter.bi_sector = map_swap_page(page, &bio->bi_bdev);
+		struct block_device *bdev;
+
+		bio->bi_iter.bi_sector = map_swap_page(page, &bdev);
+		bio_set_dev(bio, bdev);
 		bio->bi_iter.bi_sector <<= PAGE_SHIFT - 9;
 		bio->bi_end_io = end_io;
 
@@ -57,8 +60,7 @@ void end_swap_bio_write(struct bio *bio)
 		 */
 		set_page_dirty(page);
 		pr_alert("Write-error on swap-device (%u:%u:%llu)\n",
-			 imajor(bio->bi_bdev->bd_inode),
-			 iminor(bio->bi_bdev->bd_inode),
+			 MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)),
 			 (unsigned long long)bio->bi_iter.bi_sector);
 		ClearPageReclaim(page);
 	}
@@ -123,8 +125,7 @@ static void end_swap_bio_read(struct bio *bio)
 		SetPageError(page);
 		ClearPageUptodate(page);
 		pr_alert("Read-error on swap-device (%u:%u:%llu)\n",
-			 imajor(bio->bi_bdev->bd_inode),
-			 iminor(bio->bi_bdev->bd_inode),
+			 MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)),
 			 (unsigned long long)bio->bi_iter.bi_sector);
 		goto out;
 	}
@@ -338,7 +339,7 @@ int swap_readpage(struct page *page, bool do_poll)
 	int ret = 0;
 	struct swap_info_struct *sis = page_swap_info(page);
 	blk_qc_t qc;
-	struct block_device *bdev;
+	struct gendisk *disk;
 
 	VM_BUG_ON_PAGE(!PageSwapCache(page), page);
 	VM_BUG_ON_PAGE(!PageLocked(page), page);
@@ -377,7 +378,7 @@ int swap_readpage(struct page *page, bool do_poll)
 		ret = -ENOMEM;
 		goto out;
 	}
-	bdev = bio->bi_bdev;
+	disk = bio->bi_disk;
 	bio->bi_private = current;
 	bio_set_op_attrs(bio, REQ_OP_READ, 0);
 	count_vm_event(PSWPIN);
@@ -388,7 +389,7 @@ int swap_readpage(struct page *page, bool do_poll)
 		if (!READ_ONCE(bio->bi_private))
 			break;
 
-		if (!blk_mq_poll(bdev_get_queue(bdev), qc))
+		if (!blk_mq_poll(disk->queue, qc))
 			break;
 	}
 	__set_current_state(TASK_RUNNING);