Correct allowed raid levels on balance.

Raid5 with 3 devices is well defined while the old logic allowed
raid5 only with a minimum of 4 devices when converting the block group
profile via btrfs balance. Creating a raid5 with just three devices
using mkfs.btrfs worked always as expected. This is now fixed and the
whole logic is rewritten.

Signed-off-by: Andreas Philipp <philipp.andreas@gmail.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

1 files changed, 6 insertions, 7 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index a191bac31d85..062e93069c5e 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -3120,14 +3120,13 @@ int btrfs_balance(struct btrfs_balance_control *bctl,
         allowed = BTRFS_AVAIL_ALLOC_BIT_SINGLE;
         if (num_devices == 1)
                 allowed |= BTRFS_BLOCK_GROUP_DUP;
-        else if (num_devices < 4)
+        else if (num_devices > 1)
                 allowed |= (BTRFS_BLOCK_GROUP_RAID0 | BTRFS_BLOCK_GROUP_RAID1);
-        else
-                allowed |= (BTRFS_BLOCK_GROUP_RAID0 | BTRFS_BLOCK_GROUP_RAID1 |
-                                BTRFS_BLOCK_GROUP_RAID10 |
-                                BTRFS_BLOCK_GROUP_RAID5 |
-                                BTRFS_BLOCK_GROUP_RAID6);
-
+        if (num_devices > 2)
+                allowed |= BTRFS_BLOCK_GROUP_RAID5;
+        if (num_devices > 3)
+                allowed |= (BTRFS_BLOCK_GROUP_RAID10 |
+                            BTRFS_BLOCK_GROUP_RAID6);
         if ((bctl->data.flags & BTRFS_BALANCE_ARGS_CONVERT) &&
             (!alloc_profile_is_valid(bctl->data.target, 1) ||
              (bctl->data.target & ~allowed))) {