Re: [PATCH RFC 3/8] fs: refuse to claim any frozen block device

[Jan Kara]

On Tue 02-06-26 12:10:09, Christian Brauner wrote:
> setup_bdev_super() already refuses to bring a filesystem up on a frozen
> block device but only for the primary device. Now that filesystems claim
> every device through fs_bdev_file_open_by_{dev,path}(), do that check
> once in the registration helper so it covers all of them.
> 
> Drop the now-redundant check from setup_bdev_super().
> 
> Signed-off-by: Christian Brauner (Amutable) <brauner@xxxxxxxxxx>
> ---
>  fs/super.c | 21 +++++++++++----------
>  1 file changed, 11 insertions(+), 10 deletions(-)
> 
> diff --git a/fs/super.c b/fs/super.c
> index e0174d5819a0..cea743f699e4 100644
> --- a/fs/super.c
> +++ b/fs/super.c
> @@ -1690,6 +1690,17 @@ static int fs_bdev_register(struct file *bdev_file, struct super_block *sb)
>  	sb->s_count++;
>  	spin_unlock(&sb_lock);
>  
> +	/*
> +	 * Don't bring a filesystem up on a frozen device.  The entry is already
> +	 * published, so a freeze either is seen here or finds it and waits in
> +	 * super_lock() until this mount is born or (on -EBUSY) dies.  The mount
> +	 * aborts, so the entry is torn down without rebalancing @fs_bdev_active.
> +	 */
> +	if (atomic_read(&file_bdev(bdev_file)->bd_fsfreeze_count) > 0) {
> +		fs_bdev_holder_put(h);
> +		return -EBUSY;
> +	}
> +
>  	return 0;
>  }

Shouldn't this check be common also for the branch where we only increase
the refcount? Or is a filesystem where a superblock claims the bdev
multiple times and can get frozen inbetween too insane?

								Honza
-- 
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR