The minimum number of devices for RAID5 is 2, though this is only a bit
expensive RAID1, and for RAID6 it's 3, which is a triple copy that works
only 3 devices.
mkfs.btrfs allows that and mounting such filesystem also works, so the
conversion via balance filters is inconsistent with the others and we
should not prevent it.
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
---
fs/btrfs/volumes.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 8508f6028c8d..10f7de0cc7e6 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -4080,11 +4080,12 @@ int btrfs_balance(struct btrfs_fs_info *fs_info,
allowed = BTRFS_AVAIL_ALLOC_BIT_SINGLE | BTRFS_BLOCK_GROUP_DUP;
if (num_devices > 1)
allowed |= (BTRFS_BLOCK_GROUP_RAID0 | BTRFS_BLOCK_GROUP_RAID1);
- if (num_devices > 2)
+ if (num_devices >= 2)
allowed |= BTRFS_BLOCK_GROUP_RAID5;
+ if (num_devices >= 3)
+ allowed |= BTRFS_BLOCK_GROUP_RAID6;
if (num_devices > 3)
- allowed |= (BTRFS_BLOCK_GROUP_RAID10 |
- BTRFS_BLOCK_GROUP_RAID6);
+ allowed |= BTRFS_BLOCK_GROUP_RAID10;
if (validate_convert_profile(&bctl->data, allowed)) {
int index = btrfs_bg_flags_to_raid_index(bctl->data.target);
--
2.21.0
