Resending, as I received no comments on previous submission. 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 loose everything if 1 disk fails. It should give a warning in these cases.
This patch is a follow up to [PATCH v2] btrfs-progs: check metadata redundancy in order to cover the case of using balance to convert to such a set of raid levels. A simple example to hit this is to create a single device fs, which will default to single:dup, then to add a second device and attempt to convert to raid1 with the command btrfs balance start -dconvert=raid1 /mnt this will result in a filesystem with raid1:dup, which will not survive the loss of one drive. I personally don't see why the tools should allow this, but in the previous thread a warning was considered sufficient. Signed-off-by: Sam Tygier <samtyg...@yahoo.co.uk> From: Sam Tygier <samtyg...@yahoo.co.uk> Date: Sat, 13 Jun 2015 18:13:06 +0100 Subject: [PATCH] Btrfs: Check metadata redundancy on balance When converting a filesystem via balance check that metadata mode is at least as redundant as the data mode. For example give warning when: -dconvert=raid1 -mconvert=single --- fs/btrfs/volumes.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index fbe7c10..a0ce1f7 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -3454,6 +3454,24 @@ static void __cancel_balance(struct btrfs_fs_info *fs_info) atomic_set(&fs_info->mutually_exclusive_operation_running, 0); } +static int group_profile_max_safe_loss(u64 flag) +{ + switch (flag & BTRFS_BLOCK_GROUP_PROFILE_MASK) { + case 0: /* single */ + case BTRFS_BLOCK_GROUP_DUP: + case BTRFS_BLOCK_GROUP_RAID0: + return 0; + case BTRFS_BLOCK_GROUP_RAID1: + case BTRFS_BLOCK_GROUP_RAID5: + case BTRFS_BLOCK_GROUP_RAID10: + return 1; + case BTRFS_BLOCK_GROUP_RAID6: + return 2; + default: + return -1; + } +} + /* * Should be called with both balance and volume mutexes held */ @@ -3572,6 +3590,12 @@ int btrfs_balance(struct btrfs_balance_control *bctl, } } while (read_seqretry(&fs_info->profiles_lock, seq)); + if (group_profile_max_safe_loss(bctl->meta.target) < + group_profile_max_safe_loss(bctl->data.target)){ + btrfs_info(fs_info, + "Warning: metatdata has lower redundancy than data\n"); + } + if (bctl->sys.flags & BTRFS_BALANCE_ARGS_CONVERT) { int num_tolerated_disk_barrier_failures; u64 target = bctl->sys.target; -- 2.4.3 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html