btrfs-progs: mkfs: check metadata redundancy

Currently BTRFS allows you to make bad choices of data and
metadata levels. For example -d raid1 -m raid0 means you can
only use half your total disk space, but will lose everything
if 1 disk fails. It should give a warning in these cases.

When making a filesystem, check that metadata mode is at least
as redundant as the data mode. For example give warning when:

	-d raid1 -m raid0

Signed-off-by: Sam Tygier <samtygier@yahoo.co.uk>
[make the check more visible in mkfs output]
Signed-off-by: David Sterba <dsterba@suse.cz>

1 files changed, 6 insertions, 0 deletions

diff --git a/mkfs.c b/mkfs.c
index c16aeb9a..83c4a6a6 100644
--- a/mkfs.c
+++ b/mkfs.c
@@ -1429,6 +1429,12 @@ int main(int ac, char **av)
 			nodesize * i;
 	}
 
+	if (group_profile_max_safe_loss(metadata_profile) <
+		group_profile_max_safe_loss(data_profile)){
+		fprintf(stderr,
+			"WARNING: metatdata has lower redundancy than data!\n\n");
+	}
+
 	/*
 	 * FS features that can be set by other means than -O
 	 * just set the bit here