>
> +static struct super_block *get_bdev_super(const struct block_device *bdev)
> +{
> + struct super_block *sb_bdev = bdev->bd_holder, *sb = NULL;
> +
> + if (!sb_bdev)
> + return NULL;
> + if (super_lock_excl(sb_bdev) && atomic_inc_not_zero(&sb_bdev->s_active))
> + sb = sb_bdev;
> + super_unlock_excl(sb_bdev);
> + return sb;
I find the flow here a bit confusing, because to me sb_bdev implies
the super_block of the bdev fs, and because the super_lock_excl calling
convention that always locks no matter of the return value is very
confusing. Maybe at least rename sb_bdev to holder_bdev?
> +static int fs_bdev_freeze(struct block_device *bdev)
> + __releases(&bdev->bd_holder_lock)
> +{
> + struct super_block *sb;
> + int error = 0;
> +
> + lockdep_assert_held(&bdev->bd_holder_lock);
> +
> + sb = get_bdev_super(bdev);
> + if (sb) {
We always have a sb in bdev->bd_holder. So the only way get_bdev_super
could return NULL is if we can't get an active reference or the fs is
marked as SB_DYING. I think the best is to just give up and not even
bother with the sync, which is going to cause more problems than it
could help. I think we're better off just straight returning an
error here, and don't bother with the sync_blockdev.
