btrfs: Consider system chunk array size for new SYSTEM chunks

For SYSTEM chunks, despite the regular chunk item size limit, there is
another limit due to system chunk array size.

The extra limit was removed in a refactoring, so add it back.

Fixes: e3ecdb3f ("btrfs: factor out devs_max setting in __btrfs_alloc_chunk")
CC: stable@vger.kernel.org # 5.3+
Reviewed-by: NNikolay Borisov <nborisov@suse.com>
Reviewed-by: NAnand Jain <anand.jain@oracle.com>
Signed-off-by: NQu Wenruo <wqu@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/volumes.c

@@ -4967,6 +4967,7 @@ static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
 	} else if (type & BTRFS_BLOCK_GROUP_SYSTEM) {
 		max_stripe_size = SZ_32M;
 		max_chunk_size = 2 * max_stripe_size;
+		devs_max = min_t(int, devs_max, BTRFS_MAX_DEVS_SYS_CHUNK);
 	} else {
 		btrfs_err(info, "invalid chunk type 0x%llx requested",
 		       type);