btrfs: if we're restriping, use the target restripe profile

Previously we depended on some weird behavior in our chunk allocator to
force the allocation of new stripes, so by the time we got to doing the
reduce we would usually already have a chunk with the proper target.

However that behavior causes other problems and needs to be removed.
First however we need to remove this check to only restripe if we
already have those available profiles, because if we're allocating our
first chunk it obviously will not be available.  Simply use the target
as specified, and if that fails it'll be because we're out of space.
Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/block-group.c

@@ -65,12 +65,9 @@ static u64 btrfs_reduce_alloc_profile(struct btrfs_fs_info *fs_info, u64 flags)
 	spin_lock(&fs_info->balance_lock);
 	target = get_restripe_target(fs_info, flags);
 	if (target) {
-		/* Pick target profile only if it's already available */
-		if ((flags & target) & BTRFS_EXTENDED_PROFILE_MASK) {
 		spin_unlock(&fs_info->balance_lock);
 		return extended_to_chunk(target);
 	}
-	}
 	spin_unlock(&fs_info->balance_lock);
 
 	/* First, mask out the RAID levels which aren't possible */