[PATCH 2/2] btrfs: stop using write_one_page in btrfs_scratch_superblock

[Christoph Hellwig <hch@lst.de>]

write_one_page is an awkward interface that expects the page locked
and ->writepage to be implemented.  Just mark the sb dirty, put
the page and then call the proper bdev helper to sync the range.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/btrfs/volumes.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 2dd7d2c5b0d80..ddf172ba67972 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2009,23 +2009,22 @@ static void btrfs_scratch_superblock(struct btrfs_fs_info *fs_info,
 				     struct block_device *bdev, int copy_num)
 {
 	struct btrfs_super_block *disk_super;
-	struct page *page;
+	const size_t len = sizeof(disk_super->magic);
+	u64 bytenr = btrfs_sb_offset(copy_num);
 	int ret;
 
-	disk_super = btrfs_read_dev_one_super(bdev, copy_num, false);
+	disk_super = btrfs_read_disk_super(bdev, bytenr, bytenr);
 	if (IS_ERR(disk_super))
 		return;
-	memset(&disk_super->magic, 0, sizeof(disk_super->magic));
-	page = virt_to_page(disk_super);
-	set_page_dirty(page);
-	lock_page(page);
-	/* write_on_page() unlocks the page */
-	ret = write_one_page(page);
+	memset(&disk_super->magic, 0, len);
+	set_page_dirty(virt_to_page(disk_super));
+	btrfs_release_disk_super(disk_super);
+
+	ret = sync_blockdev_range(bdev, bytenr, bytenr + len - 1);
 	if (ret)
 		btrfs_warn(fs_info,
 			"error clearing superblock number %d (%d)",
 			copy_num, ret);
-	btrfs_release_disk_super(disk_super);
 }
 
 void btrfs_scratch_superblocks(struct btrfs_fs_info *fs_info,
-- 
2.30.2