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btrfs: add support for 4-copy replication (raid1c4)

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Add new block group profile to store 4 copies in a simliar way that
current RAID1 does.  The profile attributes and constraints are defined
in the raid table and used by the same code that already handles the 2-
and 3-copy RAID1.

The minimum number of devices is 4, the maximum number of devices/chunks
that can be lost/damaged is 3. There is no comparable traditional RAID
level, the profile is added for future needs to accompany triple-parity
and beyond.

Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
David Sterba
2018-03-02 22:56:53 +01:00
parent 47e6f7423b
commit 8d6fac0087
6 changed files with 24 additions and 3 deletions
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2
fs/btrfs/super.c
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@@ -1937,6 +1937,8 @@ static inline int btrfs_calc_avail_data_space(struct btrfs_fs_info *fs_info,
num_stripes = 2;
else if (type & BTRFS_BLOCK_GROUP_RAID1C3)
num_stripes = 3;
else if (type & BTRFS_BLOCK_GROUP_RAID1C4)
num_stripes = 4;
else if (type & BTRFS_BLOCK_GROUP_RAID10)
num_stripes = 4;