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btrfs: allow balancing to dup with multi-device

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Currently, we don't allow the user to try and rebalance to a dup profile
on a multi-device filesystem.  In most cases, this is a perfectly sensible
restriction as raid1 uses the same amount of space and provides better
protection.

However, when reshaping a multi-device filesystem down to a single device
filesystem, this requires the user to convert metadata and system chunks
to single profile before deleting devices, and then convert again to dup,
which leaves a period of time where metadata integrity is reduced.

This patch removes the single-device-only restriction from converting to
dup profile to remove this potential data integrity reduction.

Signed-off-by: Austin S. Hemmelgarn <ahferroin7@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Austin S. Hemmelgarn 2016-03-23 14:22:59 -04:00 committed by David Sterba
parent cf25ce518e
commit 88be159c90
1 changed files with 2 additions and 4 deletions
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6
fs/btrfs/volumes.c
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@ -3700,10 +3700,8 @@ int btrfs_balance(struct btrfs_balance_control *bctl,
num_devices--;
}
btrfs_dev_replace_unlock(&fs_info->dev_replace, 0);
allowed = BTRFS_AVAIL_ALLOC_BIT_SINGLE;
if (num_devices == 1)
allowed |= BTRFS_BLOCK_GROUP_DUP;
else if (num_devices > 1)
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)
allowed |= BTRFS_BLOCK_GROUP_RAID5;