btrfs: s_bdev is not null after missing replace

Yauhen reported in the ML that s_bdev is null at mount, and
s_bdev gets updated to some device when missing device is
replaced, as because bdev is null for missing device, things
gets matched up. Fix this by checking if s_bdev is set. I
didn't want to completely remove updating s_bdev because
the future multi device support at vfs layer may need it.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reported-by: Yauhen Kharuzhy <yauhen.kharuzhy@zavadatar.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
index 5aebedf12b5f..c93eec9ca433 100644
--- a/fs/btrfs/dev-replace.c
+++ b/fs/btrfs/dev-replace.c
@@ -569,7 +569,8 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
         ASSERT(list_empty(&src_device->resized_list));
         tgt_device->commit_total_bytes = src_device->commit_total_bytes;
         tgt_device->commit_bytes_used = src_device->bytes_used;
-        if (fs_info->sb->s_bdev == src_device->bdev)
+        if (fs_info->sb->s_bdev &&
+                (fs_info->sb->s_bdev == src_device->bdev))
                 fs_info->sb->s_bdev = tgt_device->bdev;
         if (fs_info->fs_devices->latest_bdev == src_device->bdev)
                 fs_info->fs_devices->latest_bdev = tgt_device->bdev;