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

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

View file

@ -833,6 +833,7 @@ enum btrfs_err_code {
BTRFS_ERROR_DEV_ONLY_WRITABLE,
BTRFS_ERROR_DEV_EXCL_RUN_IN_PROGRESS,
BTRFS_ERROR_DEV_RAID1C3_MIN_NOT_MET,
BTRFS_ERROR_DEV_RAID1C4_MIN_NOT_MET,
};
#define BTRFS_IOC_SNAP_CREATE _IOW(BTRFS_IOCTL_MAGIC, 1, \