btrfs: get bdev directly from fs_devices in submit_extent_page

This is preparatory patch to remove @bdev parameter from
submit_extent_page. It can't be removed completely, because the cgroups
need it for wbc when initializing the bio

wbc_init_bio
  bio_associate_blkg_from_css
    dereference bdev->bi_disk->queue

The bdev pointer is the same as latest_bdev, thus no functional change.
We can retrieve it from fs_devices that's reachable through several
dereferences. The local variable shadows the parameter, but that's only
temporary.

Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index ceb3c02..9a2339a 100644 (file)
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2987,13 +2987,16 @@ static int submit_extent_page(unsigned int opf, struct extent_io_tree *tree,
        }
 
        bio = btrfs_bio_alloc(offset);
-       bio_set_dev(bio, bdev);
        bio_add_page(bio, page, page_size, pg_offset);
        bio->bi_end_io = end_io_func;
        bio->bi_private = tree;
        bio->bi_write_hint = page->mapping->host->i_write_hint;
        bio->bi_opf = opf;
        if (wbc) {
+               struct block_device *bdev;
+
+               bdev = BTRFS_I(page->mapping->host)->root->fs_info->fs_devices->latest_bdev;
+               bio_set_dev(bio, bdev);
                wbc_init_bio(wbc, bio);
                wbc_account_cgroup_owner(wbc, page, page_size);
        }